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freebsd-skq/sys/kern/subr_witness.c
mjg afeeba244b devfs: introduce a per-dev lock to protect ->si_devsw 
This allows bumping threadcount without taking the global devmtx lock.

In particular this eliminates contention on said lock while using bhyve
with multiple vms.

Reviewed by:	kib
Tested by:	markj
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D22548
2019-11-30 16:46:19 +00:00

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/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 2008 Isilon Systems, Inc.
* Copyright (c) 2008 Ilya Maykov <ivmaykov@gmail.com>
* Copyright (c) 1998 Berkeley Software Design, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Berkeley Software Design Inc's name may not be used to endorse or
* promote products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
* and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
*/
/*
* Implementation of the `witness' lock verifier. Originally implemented for
* mutexes in BSD/OS. Extended to handle generic lock objects and lock
* classes in FreeBSD.
*/
/*
* Main Entry: witness
* Pronunciation: 'wit-n&s
* Function: noun
* Etymology: Middle English witnesse, from Old English witnes knowledge,
* testimony, witness, from 2wit
* Date: before 12th century
* 1 : attestation of a fact or event : TESTIMONY
* 2 : one that gives evidence; specifically : one who testifies in
* a cause or before a judicial tribunal
* 3 : one asked to be present at a transaction so as to be able to
* testify to its having taken place
* 4 : one who has personal knowledge of something
* 5 a : something serving as evidence or proof : SIGN
* b : public affirmation by word or example of usually
* religious faith or conviction <the heroic witness to divine
* life -- Pilot>
* 6 capitalized : a member of the Jehovah's Witnesses
*/
/*
* Special rules concerning Giant and lock orders:
*
* 1) Giant must be acquired before any other mutexes. Stated another way,
* no other mutex may be held when Giant is acquired.
*
* 2) Giant must be released when blocking on a sleepable lock.
*
* This rule is less obvious, but is a result of Giant providing the same
* semantics as spl(). Basically, when a thread sleeps, it must release
* Giant. When a thread blocks on a sleepable lock, it sleeps. Hence rule
* 2).
*
* 3) Giant may be acquired before or after sleepable locks.
*
* This rule is also not quite as obvious. Giant may be acquired after
* a sleepable lock because it is a non-sleepable lock and non-sleepable
* locks may always be acquired while holding a sleepable lock. The second
* case, Giant before a sleepable lock, follows from rule 2) above. Suppose
* you have two threads T1 and T2 and a sleepable lock X. Suppose that T1
* acquires X and blocks on Giant. Then suppose that T2 acquires Giant and
* blocks on X. When T2 blocks on X, T2 will release Giant allowing T1 to
* execute. Thus, acquiring Giant both before and after a sleepable lock
* will not result in a lock order reversal.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include "opt_hwpmc_hooks.h"
#include "opt_stack.h"
#include "opt_witness.h"
#include <sys/param.h>
#include <sys/bus.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/sbuf.h>
#include <sys/sched.h>
#include <sys/stack.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#ifdef DDB
#include <ddb/ddb.h>
#endif
#include <machine/stdarg.h>
#if !defined(DDB) && !defined(STACK)
#error "DDB or STACK options are required for WITNESS"
#endif
/* Note that these traces do not work with KTR_ALQ. */
#if 0
#define KTR_WITNESS KTR_SUBSYS
#else
#define KTR_WITNESS 0
#endif
#define LI_RECURSEMASK 0x0000ffff /* Recursion depth of lock instance. */
#define LI_EXCLUSIVE 0x00010000 /* Exclusive lock instance. */
#define LI_NORELEASE 0x00020000 /* Lock not allowed to be released. */
#define LI_SLEEPABLE 0x00040000 /* Lock may be held while sleeping. */
#ifndef WITNESS_COUNT
#define WITNESS_COUNT 1536
#endif
#define WITNESS_HASH_SIZE 251 /* Prime, gives load factor < 2 */
#define WITNESS_PENDLIST (512 + (MAXCPU * 4))
/* Allocate 256 KB of stack data space */
#define WITNESS_LO_DATA_COUNT 2048
/* Prime, gives load factor of ~2 at full load */
#define WITNESS_LO_HASH_SIZE 1021
/*
* XXX: This is somewhat bogus, as we assume here that at most 2048 threads
* will hold LOCK_NCHILDREN locks. We handle failure ok, and we should
* probably be safe for the most part, but it's still a SWAG.
*/
#define LOCK_NCHILDREN 5
#define LOCK_CHILDCOUNT 2048
#define MAX_W_NAME 64
#define FULLGRAPH_SBUF_SIZE 512
/*
* These flags go in the witness relationship matrix and describe the
* relationship between any two struct witness objects.
*/
#define WITNESS_UNRELATED 0x00 /* No lock order relation. */
#define WITNESS_PARENT 0x01 /* Parent, aka direct ancestor. */
#define WITNESS_ANCESTOR 0x02 /* Direct or indirect ancestor. */
#define WITNESS_CHILD 0x04 /* Child, aka direct descendant. */
#define WITNESS_DESCENDANT 0x08 /* Direct or indirect descendant. */
#define WITNESS_ANCESTOR_MASK (WITNESS_PARENT | WITNESS_ANCESTOR)
#define WITNESS_DESCENDANT_MASK (WITNESS_CHILD | WITNESS_DESCENDANT)
#define WITNESS_RELATED_MASK \
(WITNESS_ANCESTOR_MASK | WITNESS_DESCENDANT_MASK)
#define WITNESS_REVERSAL 0x10 /* A lock order reversal has been
* observed. */
#define WITNESS_RESERVED1 0x20 /* Unused flag, reserved. */
#define WITNESS_RESERVED2 0x40 /* Unused flag, reserved. */
#define WITNESS_LOCK_ORDER_KNOWN 0x80 /* This lock order is known. */
/* Descendant to ancestor flags */
#define WITNESS_DTOA(x) (((x) & WITNESS_RELATED_MASK) >> 2)
/* Ancestor to descendant flags */
#define WITNESS_ATOD(x) (((x) & WITNESS_RELATED_MASK) << 2)
#define WITNESS_INDEX_ASSERT(i) \
MPASS((i) > 0 && (i) <= w_max_used_index && (i) < witness_count)
static MALLOC_DEFINE(M_WITNESS, "Witness", "Witness");
/*
* Lock instances. A lock instance is the data associated with a lock while
* it is held by witness. For example, a lock instance will hold the
* recursion count of a lock. Lock instances are held in lists. Spin locks
* are held in a per-cpu list while sleep locks are held in per-thread list.
*/
struct lock_instance {
struct lock_object *li_lock;
const char *li_file;
int li_line;
u_int li_flags;
};
/*
* A simple list type used to build the list of locks held by a thread
* or CPU. We can't simply embed the list in struct lock_object since a
* lock may be held by more than one thread if it is a shared lock. Locks
* are added to the head of the list, so we fill up each list entry from
* "the back" logically. To ease some of the arithmetic, we actually fill
* in each list entry the normal way (children[0] then children[1], etc.) but
* when we traverse the list we read children[count-1] as the first entry
* down to children[0] as the final entry.
*/
struct lock_list_entry {
struct lock_list_entry *ll_next;
struct lock_instance ll_children[LOCK_NCHILDREN];
u_int ll_count;
};
/*
* The main witness structure. One of these per named lock type in the system
* (for example, "vnode interlock").
*/
struct witness {
char w_name[MAX_W_NAME];
uint32_t w_index; /* Index in the relationship matrix */
struct lock_class *w_class;
STAILQ_ENTRY(witness) w_list; /* List of all witnesses. */
STAILQ_ENTRY(witness) w_typelist; /* Witnesses of a type. */
struct witness *w_hash_next; /* Linked list in hash buckets. */
const char *w_file; /* File where last acquired */
uint32_t w_line; /* Line where last acquired */
uint32_t w_refcount;
uint16_t w_num_ancestors; /* direct/indirect
* ancestor count */
uint16_t w_num_descendants; /* direct/indirect
* descendant count */
int16_t w_ddb_level;
unsigned w_displayed:1;
unsigned w_reversed:1;
};
STAILQ_HEAD(witness_list, witness);
/*
* The witness hash table. Keys are witness names (const char *), elements are
* witness objects (struct witness *).
*/
struct witness_hash {
struct witness *wh_array[WITNESS_HASH_SIZE];
uint32_t wh_size;
uint32_t wh_count;
};
/*
* Key type for the lock order data hash table.
*/
struct witness_lock_order_key {
uint16_t from;
uint16_t to;
};
struct witness_lock_order_data {
struct stack wlod_stack;
struct witness_lock_order_key wlod_key;
struct witness_lock_order_data *wlod_next;
};
/*
* The witness lock order data hash table. Keys are witness index tuples
* (struct witness_lock_order_key), elements are lock order data objects
* (struct witness_lock_order_data).
*/
struct witness_lock_order_hash {
struct witness_lock_order_data *wloh_array[WITNESS_LO_HASH_SIZE];
u_int wloh_size;
u_int wloh_count;
};
struct witness_blessed {
const char *b_lock1;
const char *b_lock2;
};
struct witness_pendhelp {
const char *wh_type;
struct lock_object *wh_lock;
};
struct witness_order_list_entry {
const char *w_name;
struct lock_class *w_class;
};
/*
* Returns 0 if one of the locks is a spin lock and the other is not.
* Returns 1 otherwise.
*/
static __inline int
witness_lock_type_equal(struct witness *w1, struct witness *w2)
{
return ((w1->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) ==
(w2->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)));
}
static __inline int
witness_lock_order_key_equal(const struct witness_lock_order_key *a,
const struct witness_lock_order_key *b)
{
return (a->from == b->from && a->to == b->to);
}
static int _isitmyx(struct witness *w1, struct witness *w2, int rmask,
const char *fname);
static void adopt(struct witness *parent, struct witness *child);
static int blessed(struct witness *, struct witness *);
static void depart(struct witness *w);
static struct witness *enroll(const char *description,
struct lock_class *lock_class);
static struct lock_instance *find_instance(struct lock_list_entry *list,
const struct lock_object *lock);
static int isitmychild(struct witness *parent, struct witness *child);
static int isitmydescendant(struct witness *parent, struct witness *child);
static void itismychild(struct witness *parent, struct witness *child);
static int sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS);
static int sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS);
static int sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS);
static int sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS);
static void witness_add_fullgraph(struct sbuf *sb, struct witness *parent);
#ifdef DDB
static void witness_ddb_compute_levels(void);
static void witness_ddb_display(int(*)(const char *fmt, ...));
static void witness_ddb_display_descendants(int(*)(const char *fmt, ...),
struct witness *, int indent);
static void witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
struct witness_list *list);
static void witness_ddb_level_descendants(struct witness *parent, int l);
static void witness_ddb_list(struct thread *td);
#endif
static void witness_debugger(int cond, const char *msg);
static void witness_free(struct witness *m);
static struct witness *witness_get(void);
static uint32_t witness_hash_djb2(const uint8_t *key, uint32_t size);
static struct witness *witness_hash_get(const char *key);
static void witness_hash_put(struct witness *w);
static void witness_init_hash_tables(void);
static void witness_increment_graph_generation(void);
static void witness_lock_list_free(struct lock_list_entry *lle);
static struct lock_list_entry *witness_lock_list_get(void);
static int witness_lock_order_add(struct witness *parent,
struct witness *child);
static int witness_lock_order_check(struct witness *parent,
struct witness *child);
static struct witness_lock_order_data *witness_lock_order_get(
struct witness *parent,
struct witness *child);
static void witness_list_lock(struct lock_instance *instance,
int (*prnt)(const char *fmt, ...));
static int witness_output(const char *fmt, ...) __printflike(1, 2);
static int witness_voutput(const char *fmt, va_list ap) __printflike(1, 0);
static void witness_setflag(struct lock_object *lock, int flag, int set);
static SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW, NULL,
"Witness Locking");
/*
* If set to 0, lock order checking is disabled. If set to -1,
* witness is completely disabled. Otherwise witness performs full
* lock order checking for all locks. At runtime, lock order checking
* may be toggled. However, witness cannot be reenabled once it is
* completely disabled.
*/
static int witness_watch = 1;
SYSCTL_PROC(_debug_witness, OID_AUTO, watch, CTLFLAG_RWTUN | CTLTYPE_INT, NULL, 0,
sysctl_debug_witness_watch, "I", "witness is watching lock operations");
#ifdef KDB
/*
* When KDB is enabled and witness_kdb is 1, it will cause the system
* to drop into kdebug() when:
* - a lock hierarchy violation occurs
* - locks are held when going to sleep.
*/
#ifdef WITNESS_KDB
int witness_kdb = 1;
#else
int witness_kdb = 0;
#endif
SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RWTUN, &witness_kdb, 0, "");
#endif /* KDB */
#if defined(DDB) || defined(KDB)
/*
* When DDB or KDB is enabled and witness_trace is 1, it will cause the system
* to print a stack trace:
* - a lock hierarchy violation occurs
* - locks are held when going to sleep.
*/
int witness_trace = 1;
SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RWTUN, &witness_trace, 0, "");
#endif /* DDB || KDB */
#ifdef WITNESS_SKIPSPIN
int witness_skipspin = 1;
#else
int witness_skipspin = 0;
#endif
SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN, &witness_skipspin, 0, "");
int badstack_sbuf_size;
int witness_count = WITNESS_COUNT;
SYSCTL_INT(_debug_witness, OID_AUTO, witness_count, CTLFLAG_RDTUN,
&witness_count, 0, "");
/*
* Output channel for witness messages. By default we print to the console.
*/
enum witness_channel {
WITNESS_CONSOLE,
WITNESS_LOG,
WITNESS_NONE,
};
static enum witness_channel witness_channel = WITNESS_CONSOLE;
SYSCTL_PROC(_debug_witness, OID_AUTO, output_channel, CTLTYPE_STRING |
CTLFLAG_RWTUN, NULL, 0, sysctl_debug_witness_channel, "A",
"Output channel for warnings");
/*
* Call this to print out the relations between locks.
*/
SYSCTL_PROC(_debug_witness, OID_AUTO, fullgraph, CTLTYPE_STRING | CTLFLAG_RD,
NULL, 0, sysctl_debug_witness_fullgraph, "A", "Show locks relation graphs");
/*
* Call this to print out the witness faulty stacks.
*/
SYSCTL_PROC(_debug_witness, OID_AUTO, badstacks, CTLTYPE_STRING | CTLFLAG_RD,
NULL, 0, sysctl_debug_witness_badstacks, "A", "Show bad witness stacks");
static struct mtx w_mtx;
/* w_list */
static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free);
static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all);
/* w_typelist */
static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin);
static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep);
/* lock list */
static struct lock_list_entry *w_lock_list_free = NULL;
static struct witness_pendhelp pending_locks[WITNESS_PENDLIST];
static u_int pending_cnt;
static int w_free_cnt, w_spin_cnt, w_sleep_cnt;
SYSCTL_INT(_debug_witness, OID_AUTO, free_cnt, CTLFLAG_RD, &w_free_cnt, 0, "");
SYSCTL_INT(_debug_witness, OID_AUTO, spin_cnt, CTLFLAG_RD, &w_spin_cnt, 0, "");
SYSCTL_INT(_debug_witness, OID_AUTO, sleep_cnt, CTLFLAG_RD, &w_sleep_cnt, 0,
"");
static struct witness *w_data;
static uint8_t **w_rmatrix;
static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
static struct witness_hash w_hash; /* The witness hash table. */
/* The lock order data hash */
static struct witness_lock_order_data w_lodata[WITNESS_LO_DATA_COUNT];
static struct witness_lock_order_data *w_lofree = NULL;
static struct witness_lock_order_hash w_lohash;
static int w_max_used_index = 0;
static unsigned int w_generation = 0;
static const char w_notrunning[] = "Witness not running\n";
static const char w_stillcold[] = "Witness is still cold\n";
#ifdef __i386__
static const char w_notallowed[] = "The sysctl is disabled on the arch\n";
#endif
static struct witness_order_list_entry order_lists[] = {
/*
* sx locks
*/
{ "proctree", &lock_class_sx },
{ "allproc", &lock_class_sx },
{ "allprison", &lock_class_sx },
{ NULL, NULL },
/*
* Various mutexes
*/
{ "Giant", &lock_class_mtx_sleep },
{ "pipe mutex", &lock_class_mtx_sleep },
{ "sigio lock", &lock_class_mtx_sleep },
{ "process group", &lock_class_mtx_sleep },
#ifdef HWPMC_HOOKS
{ "pmc-sleep", &lock_class_mtx_sleep },
#endif
{ "process lock", &lock_class_mtx_sleep },
{ "session", &lock_class_mtx_sleep },
{ "uidinfo hash", &lock_class_rw },
{ "time lock", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* umtx
*/
{ "umtx lock", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* Sockets
*/
{ "accept", &lock_class_mtx_sleep },
{ "so_snd", &lock_class_mtx_sleep },
{ "so_rcv", &lock_class_mtx_sleep },
{ "sellck", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* Routing
*/
{ "so_rcv", &lock_class_mtx_sleep },
{ "radix node head", &lock_class_rm },
{ "rtentry", &lock_class_mtx_sleep },
{ "ifaddr", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* IPv4 multicast:
* protocol locks before interface locks, after UDP locks.
*/
{ "in_multi_sx", &lock_class_sx },
{ "udpinp", &lock_class_rw },
{ "in_multi_list_mtx", &lock_class_mtx_sleep },
{ "igmp_mtx", &lock_class_mtx_sleep },
{ "ifnet_rw", &lock_class_rw },
{ "if_addr_lock", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* IPv6 multicast:
* protocol locks before interface locks, after UDP locks.
*/
{ "in6_multi_sx", &lock_class_sx },
{ "udpinp", &lock_class_rw },
{ "in6_multi_list_mtx", &lock_class_mtx_sleep },
{ "mld_mtx", &lock_class_mtx_sleep },
{ "ifnet_rw", &lock_class_rw },
{ "if_addr_lock", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* UNIX Domain Sockets
*/
{ "unp_link_rwlock", &lock_class_rw },
{ "unp_list_lock", &lock_class_mtx_sleep },
{ "unp", &lock_class_mtx_sleep },
{ "so_snd", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* UDP/IP
*/
{ "udp", &lock_class_mtx_sleep },
{ "udpinp", &lock_class_rw },
{ "so_snd", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* TCP/IP
*/
{ "tcp", &lock_class_mtx_sleep },
{ "tcpinp", &lock_class_rw },
{ "so_snd", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* BPF
*/
{ "bpf global lock", &lock_class_sx },
{ "bpf cdev lock", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* NFS server
*/
{ "nfsd_mtx", &lock_class_mtx_sleep },
{ "so_snd", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* IEEE 802.11
*/
{ "802.11 com lock", &lock_class_mtx_sleep},
{ NULL, NULL },
/*
* Network drivers
*/
{ "network driver", &lock_class_mtx_sleep},
{ NULL, NULL },
/*
* Netgraph
*/
{ "ng_node", &lock_class_mtx_sleep },
{ "ng_worklist", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* CDEV
*/
{ "vm map (system)", &lock_class_mtx_sleep },
{ "vnode interlock", &lock_class_mtx_sleep },
{ "cdev", &lock_class_mtx_sleep },
{ "devthrd", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* VM
*/
{ "vm map (user)", &lock_class_sx },
{ "vm object", &lock_class_rw },
{ "vm page", &lock_class_mtx_sleep },
{ "pmap pv global", &lock_class_rw },
{ "pmap", &lock_class_mtx_sleep },
{ "pmap pv list", &lock_class_rw },
{ "vm page free queue", &lock_class_mtx_sleep },
{ "vm pagequeue", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* kqueue/VFS interaction
*/
{ "kqueue", &lock_class_mtx_sleep },
{ "struct mount mtx", &lock_class_mtx_sleep },
{ "vnode interlock", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* VFS namecache
*/
{ "ncvn", &lock_class_mtx_sleep },
{ "ncbuc", &lock_class_rw },
{ "vnode interlock", &lock_class_mtx_sleep },
{ "ncneg", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* ZFS locking
*/
{ "dn->dn_mtx", &lock_class_sx },
{ "dr->dt.di.dr_mtx", &lock_class_sx },
{ "db->db_mtx", &lock_class_sx },
{ NULL, NULL },
/*
* TCP log locks
*/
{ "TCP ID tree", &lock_class_rw },
{ "tcp log id bucket", &lock_class_mtx_sleep },
{ "tcpinp", &lock_class_rw },
{ "TCP log expireq", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* spin locks
*/
#ifdef SMP
{ "ap boot", &lock_class_mtx_spin },
#endif
{ "rm.mutex_mtx", &lock_class_mtx_spin },
{ "sio", &lock_class_mtx_spin },
#ifdef __i386__
{ "cy", &lock_class_mtx_spin },
#endif
#ifdef __sparc64__
{ "pcib_mtx", &lock_class_mtx_spin },
{ "rtc_mtx", &lock_class_mtx_spin },
#endif
{ "scc_hwmtx", &lock_class_mtx_spin },
{ "uart_hwmtx", &lock_class_mtx_spin },
{ "fast_taskqueue", &lock_class_mtx_spin },
{ "intr table", &lock_class_mtx_spin },
{ "process slock", &lock_class_mtx_spin },
{ "syscons video lock", &lock_class_mtx_spin },
{ "sleepq chain", &lock_class_mtx_spin },
{ "rm_spinlock", &lock_class_mtx_spin },
{ "turnstile chain", &lock_class_mtx_spin },
{ "turnstile lock", &lock_class_mtx_spin },
{ "sched lock", &lock_class_mtx_spin },
{ "td_contested", &lock_class_mtx_spin },
{ "callout", &lock_class_mtx_spin },
{ "entropy harvest mutex", &lock_class_mtx_spin },
#ifdef SMP
{ "smp rendezvous", &lock_class_mtx_spin },
#endif
#ifdef __powerpc__
{ "tlb0", &lock_class_mtx_spin },
#endif
{ NULL, NULL },
{ "sched lock", &lock_class_mtx_spin },
#ifdef HWPMC_HOOKS
{ "pmc-per-proc", &lock_class_mtx_spin },
#endif
{ NULL, NULL },
/*
* leaf locks
*/
{ "intrcnt", &lock_class_mtx_spin },
{ "icu", &lock_class_mtx_spin },
#if defined(SMP) && defined(__sparc64__)
{ "ipi", &lock_class_mtx_spin },
#endif
#ifdef __i386__
{ "allpmaps", &lock_class_mtx_spin },
{ "descriptor tables", &lock_class_mtx_spin },
#endif
{ "clk", &lock_class_mtx_spin },
{ "cpuset", &lock_class_mtx_spin },
{ "mprof lock", &lock_class_mtx_spin },
{ "zombie lock", &lock_class_mtx_spin },
{ "ALD Queue", &lock_class_mtx_spin },
#if defined(__i386__) || defined(__amd64__)
{ "pcicfg", &lock_class_mtx_spin },
{ "NDIS thread lock", &lock_class_mtx_spin },
#endif
{ "tw_osl_io_lock", &lock_class_mtx_spin },
{ "tw_osl_q_lock", &lock_class_mtx_spin },
{ "tw_cl_io_lock", &lock_class_mtx_spin },
{ "tw_cl_intr_lock", &lock_class_mtx_spin },
{ "tw_cl_gen_lock", &lock_class_mtx_spin },
#ifdef HWPMC_HOOKS
{ "pmc-leaf", &lock_class_mtx_spin },
#endif
{ "blocked lock", &lock_class_mtx_spin },
{ NULL, NULL },
{ NULL, NULL }
};
/*
* Pairs of locks which have been blessed. Witness does not complain about
* order problems with blessed lock pairs. Please do not add an entry to the
* table without an explanatory comment.
*/
static struct witness_blessed blessed_list[] = {
/*
* See the comment in ufs_dirhash.c. Basically, a vnode lock serializes
* both lock orders, so a deadlock cannot happen as a result of this
* LOR.
*/
{ "dirhash", "bufwait" },
/*
* A UFS vnode may be locked in vget() while a buffer belonging to the
* parent directory vnode is locked.
*/
{ "ufs", "bufwait" },
};
/*
* This global is set to 0 once it becomes safe to use the witness code.
*/
static int witness_cold = 1;
/*
* This global is set to 1 once the static lock orders have been enrolled
* so that a warning can be issued for any spin locks enrolled later.
*/
static int witness_spin_warn = 0;
/* Trim useless garbage from filenames. */
static const char *
fixup_filename(const char *file)
{
if (file == NULL)
return (NULL);
while (strncmp(file, "../", 3) == 0)
file += 3;
return (file);
}
/*
* Calculate the size of early witness structures.
*/
int
witness_startup_count(void)
{
int sz;
sz = sizeof(struct witness) * witness_count;
sz += sizeof(*w_rmatrix) * (witness_count + 1);
sz += sizeof(*w_rmatrix[0]) * (witness_count + 1) *
(witness_count + 1);
return (sz);
}
/*
* The WITNESS-enabled diagnostic code. Note that the witness code does
* assume that the early boot is single-threaded at least until after this
* routine is completed.
*/
void
witness_startup(void *mem)
{
struct lock_object *lock;
struct witness_order_list_entry *order;
struct witness *w, *w1;
uintptr_t p;
int i;
p = (uintptr_t)mem;
w_data = (void *)p;
p += sizeof(struct witness) * witness_count;
w_rmatrix = (void *)p;
p += sizeof(*w_rmatrix) * (witness_count + 1);
for (i = 0; i < witness_count + 1; i++) {
w_rmatrix[i] = (void *)p;
p += sizeof(*w_rmatrix[i]) * (witness_count + 1);
}
badstack_sbuf_size = witness_count * 256;
/*
* We have to release Giant before initializing its witness
* structure so that WITNESS doesn't get confused.
*/
mtx_unlock(&Giant);
mtx_assert(&Giant, MA_NOTOWNED);
CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET |
MTX_NOWITNESS | MTX_NOPROFILE);
for (i = witness_count - 1; i >= 0; i--) {
w = &w_data[i];
memset(w, 0, sizeof(*w));
w_data[i].w_index = i; /* Witness index never changes. */
witness_free(w);
}
KASSERT(STAILQ_FIRST(&w_free)->w_index == 0,
("%s: Invalid list of free witness objects", __func__));
/* Witness with index 0 is not used to aid in debugging. */
STAILQ_REMOVE_HEAD(&w_free, w_list);
w_free_cnt--;
for (i = 0; i < witness_count; i++) {
memset(w_rmatrix[i], 0, sizeof(*w_rmatrix[i]) *
(witness_count + 1));
}
for (i = 0; i < LOCK_CHILDCOUNT; i++)
witness_lock_list_free(&w_locklistdata[i]);
witness_init_hash_tables();
/* First add in all the specified order lists. */
for (order = order_lists; order->w_name != NULL; order++) {
w = enroll(order->w_name, order->w_class);
if (w == NULL)
continue;
w->w_file = "order list";
for (order++; order->w_name != NULL; order++) {
w1 = enroll(order->w_name, order->w_class);
if (w1 == NULL)
continue;
w1->w_file = "order list";
itismychild(w, w1);
w = w1;
}
}
witness_spin_warn = 1;
/* Iterate through all locks and add them to witness. */
for (i = 0; pending_locks[i].wh_lock != NULL; i++) {
lock = pending_locks[i].wh_lock;
KASSERT(lock->lo_flags & LO_WITNESS,
("%s: lock %s is on pending list but not LO_WITNESS",
__func__, lock->lo_name));
lock->lo_witness = enroll(pending_locks[i].wh_type,
LOCK_CLASS(lock));
}
/* Mark the witness code as being ready for use. */
witness_cold = 0;
mtx_lock(&Giant);
}
void
witness_init(struct lock_object *lock, const char *type)
{
struct lock_class *class;
/* Various sanity checks. */
class = LOCK_CLASS(lock);
if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
(class->lc_flags & LC_RECURSABLE) == 0)
kassert_panic("%s: lock (%s) %s can not be recursable",
__func__, class->lc_name, lock->lo_name);
if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
(class->lc_flags & LC_SLEEPABLE) == 0)
kassert_panic("%s: lock (%s) %s can not be sleepable",
__func__, class->lc_name, lock->lo_name);
if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
(class->lc_flags & LC_UPGRADABLE) == 0)
kassert_panic("%s: lock (%s) %s can not be upgradable",
__func__, class->lc_name, lock->lo_name);
/*
* If we shouldn't watch this lock, then just clear lo_witness.
* Otherwise, if witness_cold is set, then it is too early to
* enroll this lock, so defer it to witness_initialize() by adding
* it to the pending_locks list. If it is not too early, then enroll
* the lock now.
*/
if (witness_watch < 1 || panicstr != NULL ||
(lock->lo_flags & LO_WITNESS) == 0)
lock->lo_witness = NULL;
else if (witness_cold) {
pending_locks[pending_cnt].wh_lock = lock;
pending_locks[pending_cnt++].wh_type = type;
if (pending_cnt > WITNESS_PENDLIST)
panic("%s: pending locks list is too small, "
"increase WITNESS_PENDLIST\n",
__func__);
} else
lock->lo_witness = enroll(type, class);
}
void
witness_destroy(struct lock_object *lock)
{
struct lock_class *class;
struct witness *w;
class = LOCK_CLASS(lock);
if (witness_cold)
panic("lock (%s) %s destroyed while witness_cold",
class->lc_name, lock->lo_name);
/* XXX: need to verify that no one holds the lock */
if ((lock->lo_flags & LO_WITNESS) == 0 || lock->lo_witness == NULL)
return;
w = lock->lo_witness;
mtx_lock_spin(&w_mtx);
MPASS(w->w_refcount > 0);
w->w_refcount--;
if (w->w_refcount == 0)
depart(w);
mtx_unlock_spin(&w_mtx);
}
#ifdef DDB
static void
witness_ddb_compute_levels(void)
{
struct witness *w;
/*
* First clear all levels.
*/
STAILQ_FOREACH(w, &w_all, w_list)
w->w_ddb_level = -1;
/*
* Look for locks with no parents and level all their descendants.
*/
STAILQ_FOREACH(w, &w_all, w_list) {
/* If the witness has ancestors (is not a root), skip it. */
if (w->w_num_ancestors > 0)
continue;
witness_ddb_level_descendants(w, 0);
}
}
static void
witness_ddb_level_descendants(struct witness *w, int l)
{
int i;
if (w->w_ddb_level >= l)
return;
w->w_ddb_level = l;
l++;
for (i = 1; i <= w_max_used_index; i++) {
if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
witness_ddb_level_descendants(&w_data[i], l);
}
}
static void
witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...),
struct witness *w, int indent)
{
int i;
for (i = 0; i < indent; i++)
prnt(" ");
prnt("%s (type: %s, depth: %d, active refs: %d)",
w->w_name, w->w_class->lc_name,
w->w_ddb_level, w->w_refcount);
if (w->w_displayed) {
prnt(" -- (already displayed)\n");
return;
}
w->w_displayed = 1;
if (w->w_file != NULL && w->w_line != 0)
prnt(" -- last acquired @ %s:%d\n", fixup_filename(w->w_file),
w->w_line);
else
prnt(" -- never acquired\n");
indent++;
WITNESS_INDEX_ASSERT(w->w_index);
for (i = 1; i <= w_max_used_index; i++) {
if (db_pager_quit)
return;
if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
witness_ddb_display_descendants(prnt, &w_data[i],
indent);
}
}
static void
witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
struct witness_list *list)
{
struct witness *w;
STAILQ_FOREACH(w, list, w_typelist) {
if (w->w_file == NULL || w->w_ddb_level > 0)
continue;
/* This lock has no anscestors - display its descendants. */
witness_ddb_display_descendants(prnt, w, 0);
if (db_pager_quit)
return;
}
}
static void
witness_ddb_display(int(*prnt)(const char *fmt, ...))
{
struct witness *w;
KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
witness_ddb_compute_levels();
/* Clear all the displayed flags. */
STAILQ_FOREACH(w, &w_all, w_list)
w->w_displayed = 0;
/*
* First, handle sleep locks which have been acquired at least
* once.
*/
prnt("Sleep locks:\n");
witness_ddb_display_list(prnt, &w_sleep);
if (db_pager_quit)
return;
/*
* Now do spin locks which have been acquired at least once.
*/
prnt("\nSpin locks:\n");
witness_ddb_display_list(prnt, &w_spin);
if (db_pager_quit)
return;
/*
* Finally, any locks which have not been acquired yet.
*/
prnt("\nLocks which were never acquired:\n");
STAILQ_FOREACH(w, &w_all, w_list) {
if (w->w_file != NULL || w->w_refcount == 0)
continue;
prnt("%s (type: %s, depth: %d)\n", w->w_name,
w->w_class->lc_name, w->w_ddb_level);
if (db_pager_quit)
return;
}
}
#endif /* DDB */
int
witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
{
if (witness_watch == -1 || panicstr != NULL)
return (0);
/* Require locks that witness knows about. */
if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
lock2->lo_witness == NULL)
return (EINVAL);
mtx_assert(&w_mtx, MA_NOTOWNED);
mtx_lock_spin(&w_mtx);
/*
* If we already have either an explicit or implied lock order that
* is the other way around, then return an error.
*/
if (witness_watch &&
isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
mtx_unlock_spin(&w_mtx);
return (EDOOFUS);
}
/* Try to add the new order. */
CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
lock2->lo_witness->w_name, lock1->lo_witness->w_name);
itismychild(lock1->lo_witness, lock2->lo_witness);
mtx_unlock_spin(&w_mtx);
return (0);
}
void
witness_checkorder(struct lock_object *lock, int flags, const char *file,
int line, struct lock_object *interlock)
{
struct lock_list_entry *lock_list, *lle;
struct lock_instance *lock1, *lock2, *plock;
struct lock_class *class, *iclass;
struct witness *w, *w1;
struct thread *td;
int i, j;
if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL ||
panicstr != NULL)
return;
w = lock->lo_witness;
class = LOCK_CLASS(lock);
td = curthread;
if (class->lc_flags & LC_SLEEPLOCK) {
/*
* Since spin locks include a critical section, this check
* implicitly enforces a lock order of all sleep locks before
* all spin locks.
*/
if (td->td_critnest != 0 && !kdb_active)
kassert_panic("acquiring blockable sleep lock with "
"spinlock or critical section held (%s) %s @ %s:%d",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
/*
* If this is the first lock acquired then just return as
* no order checking is needed.
*/
lock_list = td->td_sleeplocks;
if (lock_list == NULL || lock_list->ll_count == 0)
return;
} else {
/*
* If this is the first lock, just return as no order
* checking is needed. Avoid problems with thread
* migration pinning the thread while checking if
* spinlocks are held. If at least one spinlock is held
* the thread is in a safe path and it is allowed to
* unpin it.
*/
sched_pin();
lock_list = PCPU_GET(spinlocks);
if (lock_list == NULL || lock_list->ll_count == 0) {
sched_unpin();
return;
}
sched_unpin();
}
/*
* Check to see if we are recursing on a lock we already own. If
* so, make sure that we don't mismatch exclusive and shared lock
* acquires.
*/
lock1 = find_instance(lock_list, lock);
if (lock1 != NULL) {
if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
(flags & LOP_EXCLUSIVE) == 0) {
witness_output("shared lock of (%s) %s @ %s:%d\n",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
witness_output("while exclusively locked from %s:%d\n",
fixup_filename(lock1->li_file), lock1->li_line);
kassert_panic("excl->share");
}
if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
(flags & LOP_EXCLUSIVE) != 0) {
witness_output("exclusive lock of (%s) %s @ %s:%d\n",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
witness_output("while share locked from %s:%d\n",
fixup_filename(lock1->li_file), lock1->li_line);
kassert_panic("share->excl");
}
return;
}
/* Warn if the interlock is not locked exactly once. */
if (interlock != NULL) {
iclass = LOCK_CLASS(interlock);
lock1 = find_instance(lock_list, interlock);
if (lock1 == NULL)
kassert_panic("interlock (%s) %s not locked @ %s:%d",
iclass->lc_name, interlock->lo_name,
fixup_filename(file), line);
else if ((lock1->li_flags & LI_RECURSEMASK) != 0)
kassert_panic("interlock (%s) %s recursed @ %s:%d",
iclass->lc_name, interlock->lo_name,
fixup_filename(file), line);
}
/*
* Find the previously acquired lock, but ignore interlocks.
*/
plock = &lock_list->ll_children[lock_list->ll_count - 1];
if (interlock != NULL && plock->li_lock == interlock) {
if (lock_list->ll_count > 1)
plock =
&lock_list->ll_children[lock_list->ll_count - 2];
else {
lle = lock_list->ll_next;
/*
* The interlock is the only lock we hold, so
* simply return.
*/
if (lle == NULL)
return;
plock = &lle->ll_children[lle->ll_count - 1];
}
}
/*
* Try to perform most checks without a lock. If this succeeds we
* can skip acquiring the lock and return success. Otherwise we redo
* the check with the lock held to handle races with concurrent updates.
*/
w1 = plock->li_lock->lo_witness;
if (witness_lock_order_check(w1, w))
return;
mtx_lock_spin(&w_mtx);
if (witness_lock_order_check(w1, w)) {
mtx_unlock_spin(&w_mtx);
return;
}
witness_lock_order_add(w1, w);
/*
* Check for duplicate locks of the same type. Note that we only
* have to check for this on the last lock we just acquired. Any
* other cases will be caught as lock order violations.
*/
if (w1 == w) {
i = w->w_index;
if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) &&
!(w_rmatrix[i][i] & WITNESS_REVERSAL)) {
w_rmatrix[i][i] |= WITNESS_REVERSAL;
w->w_reversed = 1;
mtx_unlock_spin(&w_mtx);
witness_output(
"acquiring duplicate lock of same type: \"%s\"\n",
w->w_name);
witness_output(" 1st %s @ %s:%d\n", plock->li_lock->lo_name,
fixup_filename(plock->li_file), plock->li_line);
witness_output(" 2nd %s @ %s:%d\n", lock->lo_name,
fixup_filename(file), line);
witness_debugger(1, __func__);
} else
mtx_unlock_spin(&w_mtx);
return;
}
mtx_assert(&w_mtx, MA_OWNED);
/*
* If we know that the lock we are acquiring comes after
* the lock we most recently acquired in the lock order tree,
* then there is no need for any further checks.
*/
if (isitmychild(w1, w))
goto out;
for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) {
for (i = lle->ll_count - 1; i >= 0; i--, j++) {
MPASS(j < LOCK_CHILDCOUNT * LOCK_NCHILDREN);
lock1 = &lle->ll_children[i];
/*
* Ignore the interlock.
*/
if (interlock == lock1->li_lock)
continue;
/*
* If this lock doesn't undergo witness checking,
* then skip it.
*/
w1 = lock1->li_lock->lo_witness;
if (w1 == NULL) {
KASSERT((lock1->li_lock->lo_flags & LO_WITNESS) == 0,
("lock missing witness structure"));
continue;
}
/*
* If we are locking Giant and this is a sleepable
* lock, then skip it.
*/
if ((lock1->li_flags & LI_SLEEPABLE) != 0 &&
lock == &Giant.lock_object)
continue;
/*
* If we are locking a sleepable lock and this lock
* is Giant, then skip it.
*/
if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
(flags & LOP_NOSLEEP) == 0 &&
lock1->li_lock == &Giant.lock_object)
continue;
/*
* If we are locking a sleepable lock and this lock
* isn't sleepable, we want to treat it as a lock
* order violation to enfore a general lock order of
* sleepable locks before non-sleepable locks.
*/
if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
(flags & LOP_NOSLEEP) == 0 &&
(lock1->li_flags & LI_SLEEPABLE) == 0)
goto reversal;
/*
* If we are locking Giant and this is a non-sleepable
* lock, then treat it as a reversal.
*/
if ((lock1->li_flags & LI_SLEEPABLE) == 0 &&
lock == &Giant.lock_object)
goto reversal;
/*
* Check the lock order hierarchy for a reveresal.
*/
if (!isitmydescendant(w, w1))
continue;
reversal:
/*
* We have a lock order violation, check to see if it
* is allowed or has already been yelled about.
*/
/* Bail if this violation is known */
if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL)
goto out;
/* Record this as a violation */
w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL;
w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL;
w->w_reversed = w1->w_reversed = 1;
witness_increment_graph_generation();
/*
* If the lock order is blessed, bail before logging
* anything. We don't look for other lock order
* violations though, which may be a bug.
*/
if (blessed(w, w1))
goto out;
mtx_unlock_spin(&w_mtx);
#ifdef WITNESS_NO_VNODE
/*
* There are known LORs between VNODE locks. They are
* not an indication of a bug. VNODE locks are flagged
* as such (LO_IS_VNODE) and we don't yell if the LOR
* is between 2 VNODE locks.
*/
if ((lock->lo_flags & LO_IS_VNODE) != 0 &&
(lock1->li_lock->lo_flags & LO_IS_VNODE) != 0)
return;
#endif
/*
* Ok, yell about it.
*/
if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
(flags & LOP_NOSLEEP) == 0 &&
(lock1->li_flags & LI_SLEEPABLE) == 0)
witness_output(
"lock order reversal: (sleepable after non-sleepable)\n");
else if ((lock1->li_flags & LI_SLEEPABLE) == 0
&& lock == &Giant.lock_object)
witness_output(
"lock order reversal: (Giant after non-sleepable)\n");
else
witness_output("lock order reversal:\n");
/*
* Try to locate an earlier lock with
* witness w in our list.
*/
do {
lock2 = &lle->ll_children[i];
MPASS(lock2->li_lock != NULL);
if (lock2->li_lock->lo_witness == w)
break;
if (i == 0 && lle->ll_next != NULL) {
lle = lle->ll_next;
i = lle->ll_count - 1;
MPASS(i >= 0 && i < LOCK_NCHILDREN);
} else
i--;
} while (i >= 0);
if (i < 0) {
witness_output(" 1st %p %s (%s) @ %s:%d\n",
lock1->li_lock, lock1->li_lock->lo_name,
w1->w_name, fixup_filename(lock1->li_file),
lock1->li_line);
witness_output(" 2nd %p %s (%s) @ %s:%d\n", lock,
lock->lo_name, w->w_name,
fixup_filename(file), line);
} else {
witness_output(" 1st %p %s (%s) @ %s:%d\n",
lock2->li_lock, lock2->li_lock->lo_name,
lock2->li_lock->lo_witness->w_name,
fixup_filename(lock2->li_file),
lock2->li_line);
witness_output(" 2nd %p %s (%s) @ %s:%d\n",
lock1->li_lock, lock1->li_lock->lo_name,
w1->w_name, fixup_filename(lock1->li_file),
lock1->li_line);
witness_output(" 3rd %p %s (%s) @ %s:%d\n", lock,
lock->lo_name, w->w_name,
fixup_filename(file), line);
}
witness_debugger(1, __func__);
return;
}
}
/*
* If requested, build a new lock order. However, don't build a new
* relationship between a sleepable lock and Giant if it is in the
* wrong direction. The correct lock order is that sleepable locks
* always come before Giant.
*/
if (flags & LOP_NEWORDER &&
!(plock->li_lock == &Giant.lock_object &&
(lock->lo_flags & LO_SLEEPABLE) != 0 &&
(flags & LOP_NOSLEEP) == 0)) {
CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
w->w_name, plock->li_lock->lo_witness->w_name);
itismychild(plock->li_lock->lo_witness, w);
}
out:
mtx_unlock_spin(&w_mtx);
}
void
witness_lock(struct lock_object *lock, int flags, const char *file, int line)
{
struct lock_list_entry **lock_list, *lle;
struct lock_instance *instance;
struct witness *w;
struct thread *td;
if (witness_cold || witness_watch == -1 || lock->lo_witness == NULL ||
panicstr != NULL)
return;
w = lock->lo_witness;
td = curthread;
/* Determine lock list for this lock. */
if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK)
lock_list = &td->td_sleeplocks;
else
lock_list = PCPU_PTR(spinlocks);
/* Check to see if we are recursing on a lock we already own. */
instance = find_instance(*lock_list, lock);
if (instance != NULL) {
instance->li_flags++;
CTR4(KTR_WITNESS, "%s: pid %d recursed on %s r=%d", __func__,
td->td_proc->p_pid, lock->lo_name,
instance->li_flags & LI_RECURSEMASK);
instance->li_file = file;
instance->li_line = line;
return;
}
/* Update per-witness last file and line acquire. */
w->w_file = file;
w->w_line = line;
/* Find the next open lock instance in the list and fill it. */
lle = *lock_list;
if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
lle = witness_lock_list_get();
if (lle == NULL)
return;
lle->ll_next = *lock_list;
CTR3(KTR_WITNESS, "%s: pid %d added lle %p", __func__,
td->td_proc->p_pid, lle);
*lock_list = lle;
}
instance = &lle->ll_children[lle->ll_count++];
instance->li_lock = lock;
instance->li_line = line;
instance->li_file = file;
instance->li_flags = 0;
if ((flags & LOP_EXCLUSIVE) != 0)
instance->li_flags |= LI_EXCLUSIVE;
if ((lock->lo_flags & LO_SLEEPABLE) != 0 && (flags & LOP_NOSLEEP) == 0)
instance->li_flags |= LI_SLEEPABLE;
CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
}
void
witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
{
struct lock_instance *instance;
struct lock_class *class;
KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
return;
class = LOCK_CLASS(lock);
if (witness_watch) {
if ((lock->lo_flags & LO_UPGRADABLE) == 0)
kassert_panic(
"upgrade of non-upgradable lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
if ((class->lc_flags & LC_SLEEPLOCK) == 0)
kassert_panic(
"upgrade of non-sleep lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
}
instance = find_instance(curthread->td_sleeplocks, lock);
if (instance == NULL) {
kassert_panic("upgrade of unlocked lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
return;
}
if (witness_watch) {
if ((instance->li_flags & LI_EXCLUSIVE) != 0)
kassert_panic(
"upgrade of exclusive lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
if ((instance->li_flags & LI_RECURSEMASK) != 0)
kassert_panic(
"upgrade of recursed lock (%s) %s r=%d @ %s:%d",
class->lc_name, lock->lo_name,
instance->li_flags & LI_RECURSEMASK,
fixup_filename(file), line);
}
instance->li_flags |= LI_EXCLUSIVE;
}
void
witness_downgrade(struct lock_object *lock, int flags, const char *file,
int line)
{
struct lock_instance *instance;
struct lock_class *class;
KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
return;
class = LOCK_CLASS(lock);
if (witness_watch) {
if ((lock->lo_flags & LO_UPGRADABLE) == 0)
kassert_panic(
"downgrade of non-upgradable lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
if ((class->lc_flags & LC_SLEEPLOCK) == 0)
kassert_panic(
"downgrade of non-sleep lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
}
instance = find_instance(curthread->td_sleeplocks, lock);
if (instance == NULL) {
kassert_panic("downgrade of unlocked lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
return;
}
if (witness_watch) {
if ((instance->li_flags & LI_EXCLUSIVE) == 0)
kassert_panic(
"downgrade of shared lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
if ((instance->li_flags & LI_RECURSEMASK) != 0)
kassert_panic(
"downgrade of recursed lock (%s) %s r=%d @ %s:%d",
class->lc_name, lock->lo_name,
instance->li_flags & LI_RECURSEMASK,
fixup_filename(file), line);
}
instance->li_flags &= ~LI_EXCLUSIVE;
}
void
witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
{
struct lock_list_entry **lock_list, *lle;
struct lock_instance *instance;
struct lock_class *class;
struct thread *td;
register_t s;
int i, j;
if (witness_cold || lock->lo_witness == NULL || panicstr != NULL)
return;
td = curthread;
class = LOCK_CLASS(lock);
/* Find lock instance associated with this lock. */
if (class->lc_flags & LC_SLEEPLOCK)
lock_list = &td->td_sleeplocks;
else
lock_list = PCPU_PTR(spinlocks);
lle = *lock_list;
for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
for (i = 0; i < (*lock_list)->ll_count; i++) {
instance = &(*lock_list)->ll_children[i];
if (instance->li_lock == lock)
goto found;
}
/*
* When disabling WITNESS through witness_watch we could end up in
* having registered locks in the td_sleeplocks queue.
* We have to make sure we flush these queues, so just search for
* eventual register locks and remove them.
*/
if (witness_watch > 0) {
kassert_panic("lock (%s) %s not locked @ %s:%d", class->lc_name,
lock->lo_name, fixup_filename(file), line);
return;
} else {
return;
}
found:
/* First, check for shared/exclusive mismatches. */
if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 &&
(flags & LOP_EXCLUSIVE) == 0) {
witness_output("shared unlock of (%s) %s @ %s:%d\n",
class->lc_name, lock->lo_name, fixup_filename(file), line);
witness_output("while exclusively locked from %s:%d\n",
fixup_filename(instance->li_file), instance->li_line);
kassert_panic("excl->ushare");
}
if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 &&
(flags & LOP_EXCLUSIVE) != 0) {
witness_output("exclusive unlock of (%s) %s @ %s:%d\n",
class->lc_name, lock->lo_name, fixup_filename(file), line);
witness_output("while share locked from %s:%d\n",
fixup_filename(instance->li_file),
instance->li_line);
kassert_panic("share->uexcl");
}
/* If we are recursed, unrecurse. */
if ((instance->li_flags & LI_RECURSEMASK) > 0) {
CTR4(KTR_WITNESS, "%s: pid %d unrecursed on %s r=%d", __func__,
td->td_proc->p_pid, instance->li_lock->lo_name,
instance->li_flags);
instance->li_flags--;
return;
}
/* The lock is now being dropped, check for NORELEASE flag */
if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) {
witness_output("forbidden unlock of (%s) %s @ %s:%d\n",
class->lc_name, lock->lo_name, fixup_filename(file), line);
kassert_panic("lock marked norelease");
}
/* Otherwise, remove this item from the list. */
s = intr_disable();
CTR4(KTR_WITNESS, "%s: pid %d removed %s from lle[%d]", __func__,
td->td_proc->p_pid, instance->li_lock->lo_name,
(*lock_list)->ll_count - 1);
for (j = i; j < (*lock_list)->ll_count - 1; j++)
(*lock_list)->ll_children[j] =
(*lock_list)->ll_children[j + 1];
(*lock_list)->ll_count--;
intr_restore(s);
/*
* In order to reduce contention on w_mtx, we want to keep always an
* head object into lists so that frequent allocation from the
* free witness pool (and subsequent locking) is avoided.
* In order to maintain the current code simple, when the head
* object is totally unloaded it means also that we do not have
* further objects in the list, so the list ownership needs to be
* hand over to another object if the current head needs to be freed.
*/
if ((*lock_list)->ll_count == 0) {
if (*lock_list == lle) {
if (lle->ll_next == NULL)
return;
} else
lle = *lock_list;
*lock_list = lle->ll_next;
CTR3(KTR_WITNESS, "%s: pid %d removed lle %p", __func__,
td->td_proc->p_pid, lle);
witness_lock_list_free(lle);
}
}
void
witness_thread_exit(struct thread *td)
{
struct lock_list_entry *lle;
int i, n;
lle = td->td_sleeplocks;
if (lle == NULL || panicstr != NULL)
return;
if (lle->ll_count != 0) {
for (n = 0; lle != NULL; lle = lle->ll_next)
for (i = lle->ll_count - 1; i >= 0; i--) {
if (n == 0)
witness_output(
"Thread %p exiting with the following locks held:\n", td);
n++;
witness_list_lock(&lle->ll_children[i],
witness_output);
}
kassert_panic(
"Thread %p cannot exit while holding sleeplocks\n", td);
}
witness_lock_list_free(lle);
}
/*
* Warn if any locks other than 'lock' are held. Flags can be passed in to
* exempt Giant and sleepable locks from the checks as well. If any
* non-exempt locks are held, then a supplied message is printed to the
* output channel along with a list of the offending locks. If indicated in the
* flags then a failure results in a panic as well.
*/
int
witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
{
struct lock_list_entry *lock_list, *lle;
struct lock_instance *lock1;
struct thread *td;
va_list ap;
int i, n;
if (witness_cold || witness_watch < 1 || panicstr != NULL)
return (0);
n = 0;
td = curthread;
for (lle = td->td_sleeplocks; lle != NULL; lle = lle->ll_next)
for (i = lle->ll_count - 1; i >= 0; i--) {
lock1 = &lle->ll_children[i];
if (lock1->li_lock == lock)
continue;
if (flags & WARN_GIANTOK &&
lock1->li_lock == &Giant.lock_object)
continue;
if (flags & WARN_SLEEPOK &&
(lock1->li_flags & LI_SLEEPABLE) != 0)
continue;
if (n == 0) {
va_start(ap, fmt);
vprintf(fmt, ap);
va_end(ap);
printf(" with the following %slocks held:\n",
(flags & WARN_SLEEPOK) != 0 ?
"non-sleepable " : "");
}
n++;
witness_list_lock(lock1, printf);
}
/*
* Pin the thread in order to avoid problems with thread migration.
* Once that all verifies are passed about spinlocks ownership,
* the thread is in a safe path and it can be unpinned.
*/
sched_pin();
lock_list = PCPU_GET(spinlocks);
if (lock_list != NULL && lock_list->ll_count != 0) {
sched_unpin();
/*
* We should only have one spinlock and as long as
* the flags cannot match for this locks class,
* check if the first spinlock is the one curthread
* should hold.
*/
lock1 = &lock_list->ll_children[lock_list->ll_count - 1];
if (lock_list->ll_count == 1 && lock_list->ll_next == NULL &&
lock1->li_lock == lock && n == 0)
return (0);
va_start(ap, fmt);
vprintf(fmt, ap);
va_end(ap);
printf(" with the following %slocks held:\n",
(flags & WARN_SLEEPOK) != 0 ? "non-sleepable " : "");
n += witness_list_locks(&lock_list, printf);
} else
sched_unpin();
if (flags & WARN_PANIC && n)
kassert_panic("%s", __func__);
else
witness_debugger(n, __func__);
return (n);
}
const char *
witness_file(struct lock_object *lock)
{
struct witness *w;
if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
return ("?");
w = lock->lo_witness;
return (w->w_file);
}
int
witness_line(struct lock_object *lock)
{
struct witness *w;
if (witness_cold || witness_watch < 1 || lock->lo_witness == NULL)
return (0);
w = lock->lo_witness;
return (w->w_line);
}
static struct witness *
enroll(const char *description, struct lock_class *lock_class)
{
struct witness *w;
MPASS(description != NULL);
if (witness_watch == -1 || panicstr != NULL)
return (NULL);
if ((lock_class->lc_flags & LC_SPINLOCK)) {
if (witness_skipspin)
return (NULL);
} else if ((lock_class->lc_flags & LC_SLEEPLOCK) == 0) {
kassert_panic("lock class %s is not sleep or spin",
lock_class->lc_name);
return (NULL);
}
mtx_lock_spin(&w_mtx);
w = witness_hash_get(description);
if (w)
goto found;
if ((w = witness_get()) == NULL)
return (NULL);
MPASS(strlen(description) < MAX_W_NAME);
strcpy(w->w_name, description);
w->w_class = lock_class;
w->w_refcount = 1;
STAILQ_INSERT_HEAD(&w_all, w, w_list);
if (lock_class->lc_flags & LC_SPINLOCK) {
STAILQ_INSERT_HEAD(&w_spin, w, w_typelist);
w_spin_cnt++;
} else if (lock_class->lc_flags & LC_SLEEPLOCK) {
STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist);
w_sleep_cnt++;
}
/* Insert new witness into the hash */
witness_hash_put(w);
witness_increment_graph_generation();
mtx_unlock_spin(&w_mtx);
return (w);
found:
w->w_refcount++;
if (w->w_refcount == 1)
w->w_class = lock_class;
mtx_unlock_spin(&w_mtx);
if (lock_class != w->w_class)
kassert_panic(
"lock (%s) %s does not match earlier (%s) lock",
description, lock_class->lc_name,
w->w_class->lc_name);
return (w);
}
static void
depart(struct witness *w)
{
MPASS(w->w_refcount == 0);
if (w->w_class->lc_flags & LC_SLEEPLOCK) {
w_sleep_cnt--;
} else {
w_spin_cnt--;
}
/*
* Set file to NULL as it may point into a loadable module.
*/
w->w_file = NULL;
w->w_line = 0;
witness_increment_graph_generation();
}
static void
adopt(struct witness *parent, struct witness *child)
{
int pi, ci, i, j;
if (witness_cold == 0)
mtx_assert(&w_mtx, MA_OWNED);
/* If the relationship is already known, there's no work to be done. */
if (isitmychild(parent, child))
return;
/* When the structure of the graph changes, bump up the generation. */
witness_increment_graph_generation();
/*
* The hard part ... create the direct relationship, then propagate all
* indirect relationships.
*/
pi = parent->w_index;
ci = child->w_index;
WITNESS_INDEX_ASSERT(pi);
WITNESS_INDEX_ASSERT(ci);
MPASS(pi != ci);
w_rmatrix[pi][ci] |= WITNESS_PARENT;
w_rmatrix[ci][pi] |= WITNESS_CHILD;
/*
* If parent was not already an ancestor of child,
* then we increment the descendant and ancestor counters.
*/
if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) {
parent->w_num_descendants++;
child->w_num_ancestors++;
}
/*
* Find each ancestor of 'pi'. Note that 'pi' itself is counted as
* an ancestor of 'pi' during this loop.
*/
for (i = 1; i <= w_max_used_index; i++) {
if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 &&
(i != pi))
continue;
/* Find each descendant of 'i' and mark it as a descendant. */
for (j = 1; j <= w_max_used_index; j++) {
/*
* Skip children that are already marked as
* descendants of 'i'.
*/
if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK)
continue;
/*
* We are only interested in descendants of 'ci'. Note
* that 'ci' itself is counted as a descendant of 'ci'.
*/
if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 &&
(j != ci))
continue;
w_rmatrix[i][j] |= WITNESS_ANCESTOR;
w_rmatrix[j][i] |= WITNESS_DESCENDANT;
w_data[i].w_num_descendants++;
w_data[j].w_num_ancestors++;
/*
* Make sure we aren't marking a node as both an
* ancestor and descendant. We should have caught
* this as a lock order reversal earlier.
*/
if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) &&
(w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) {
printf("witness rmatrix paradox! [%d][%d]=%d "
"both ancestor and descendant\n",
i, j, w_rmatrix[i][j]);
kdb_backtrace();
printf("Witness disabled.\n");
witness_watch = -1;
}
if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) &&
(w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) {
printf("witness rmatrix paradox! [%d][%d]=%d "
"both ancestor and descendant\n",
j, i, w_rmatrix[j][i]);
kdb_backtrace();
printf("Witness disabled.\n");
witness_watch = -1;
}
}
}
}
static void
itismychild(struct witness *parent, struct witness *child)
{
int unlocked;
MPASS(child != NULL && parent != NULL);
if (witness_cold == 0)
mtx_assert(&w_mtx, MA_OWNED);
if (!witness_lock_type_equal(parent, child)) {
if (witness_cold == 0) {
unlocked = 1;
mtx_unlock_spin(&w_mtx);
} else {
unlocked = 0;
}
kassert_panic(
"%s: parent \"%s\" (%s) and child \"%s\" (%s) are not "
"the same lock type", __func__, parent->w_name,
parent->w_class->lc_name, child->w_name,
child->w_class->lc_name);
if (unlocked)
mtx_lock_spin(&w_mtx);
}
adopt(parent, child);
}
/*
* Generic code for the isitmy*() functions. The rmask parameter is the
* expected relationship of w1 to w2.
*/
static int
_isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname)
{
unsigned char r1, r2;
int i1, i2;
i1 = w1->w_index;
i2 = w2->w_index;
WITNESS_INDEX_ASSERT(i1);
WITNESS_INDEX_ASSERT(i2);
r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK;
r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK;
/* The flags on one better be the inverse of the flags on the other */
if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) ||
(WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) {
/* Don't squawk if we're potentially racing with an update. */
if (!mtx_owned(&w_mtx))
return (0);
printf("%s: rmatrix mismatch between %s (index %d) and %s "
"(index %d): w_rmatrix[%d][%d] == %hhx but "
"w_rmatrix[%d][%d] == %hhx\n",
fname, w1->w_name, i1, w2->w_name, i2, i1, i2, r1,
i2, i1, r2);
kdb_backtrace();
printf("Witness disabled.\n");
witness_watch = -1;
}
return (r1 & rmask);
}
/*
* Checks if @child is a direct child of @parent.
*/
static int
isitmychild(struct witness *parent, struct witness *child)
{
return (_isitmyx(parent, child, WITNESS_PARENT, __func__));
}
/*
* Checks if @descendant is a direct or inderect descendant of @ancestor.
*/
static int
isitmydescendant(struct witness *ancestor, struct witness *descendant)
{
return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK,
__func__));
}
static int
blessed(struct witness *w1, struct witness *w2)
{
int i;
struct witness_blessed *b;
for (i = 0; i < nitems(blessed_list); i++) {
b = &blessed_list[i];
if (strcmp(w1->w_name, b->b_lock1) == 0) {
if (strcmp(w2->w_name, b->b_lock2) == 0)
return (1);
continue;
}
if (strcmp(w1->w_name, b->b_lock2) == 0)
if (strcmp(w2->w_name, b->b_lock1) == 0)
return (1);
}
return (0);
}
static struct witness *
witness_get(void)
{
struct witness *w;
int index;
if (witness_cold == 0)
mtx_assert(&w_mtx, MA_OWNED);
if (witness_watch == -1) {
mtx_unlock_spin(&w_mtx);
return (NULL);
}
if (STAILQ_EMPTY(&w_free)) {
witness_watch = -1;
mtx_unlock_spin(&w_mtx);
printf("WITNESS: unable to allocate a new witness object\n");
return (NULL);
}
w = STAILQ_FIRST(&w_free);
STAILQ_REMOVE_HEAD(&w_free, w_list);
w_free_cnt--;
index = w->w_index;
MPASS(index > 0 && index == w_max_used_index+1 &&
index < witness_count);
bzero(w, sizeof(*w));
w->w_index = index;
if (index > w_max_used_index)
w_max_used_index = index;
return (w);
}
static void
witness_free(struct witness *w)
{
STAILQ_INSERT_HEAD(&w_free, w, w_list);
w_free_cnt++;
}
static struct lock_list_entry *
witness_lock_list_get(void)
{
struct lock_list_entry *lle;
if (witness_watch == -1)
return (NULL);
mtx_lock_spin(&w_mtx);
lle = w_lock_list_free;
if (lle == NULL) {
witness_watch = -1;
mtx_unlock_spin(&w_mtx);
printf("%s: witness exhausted\n", __func__);
return (NULL);
}
w_lock_list_free = lle->ll_next;
mtx_unlock_spin(&w_mtx);
bzero(lle, sizeof(*lle));
return (lle);
}
static void
witness_lock_list_free(struct lock_list_entry *lle)
{
mtx_lock_spin(&w_mtx);
lle->ll_next = w_lock_list_free;
w_lock_list_free = lle;
mtx_unlock_spin(&w_mtx);
}
static struct lock_instance *
find_instance(struct lock_list_entry *list, const struct lock_object *lock)
{
struct lock_list_entry *lle;
struct lock_instance *instance;
int i;
for (lle = list; lle != NULL; lle = lle->ll_next)
for (i = lle->ll_count - 1; i >= 0; i--) {
instance = &lle->ll_children[i];
if (instance->li_lock == lock)
return (instance);
}
return (NULL);
}
static void
witness_list_lock(struct lock_instance *instance,
int (*prnt)(const char *fmt, ...))
{
struct lock_object *lock;
lock = instance->li_lock;
prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
"exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
if (lock->lo_witness->w_name != lock->lo_name)
prnt(" (%s)", lock->lo_witness->w_name);
prnt(" r = %d (%p) locked @ %s:%d\n",
instance->li_flags & LI_RECURSEMASK, lock,
fixup_filename(instance->li_file), instance->li_line);
}
static int
witness_output(const char *fmt, ...)
{
va_list ap;
int ret;
va_start(ap, fmt);
ret = witness_voutput(fmt, ap);
va_end(ap);
return (ret);
}
static int
witness_voutput(const char *fmt, va_list ap)
{
int ret;
ret = 0;
switch (witness_channel) {
case WITNESS_CONSOLE:
ret = vprintf(fmt, ap);
break;
case WITNESS_LOG:
vlog(LOG_NOTICE, fmt, ap);
break;
case WITNESS_NONE:
break;
}
return (ret);
}
#ifdef DDB
static int
witness_thread_has_locks(struct thread *td)
{
if (td->td_sleeplocks == NULL)
return (0);
return (td->td_sleeplocks->ll_count != 0);
}
static int
witness_proc_has_locks(struct proc *p)
{
struct thread *td;
FOREACH_THREAD_IN_PROC(p, td) {
if (witness_thread_has_locks(td))
return (1);
}
return (0);
}
#endif
int
witness_list_locks(struct lock_list_entry **lock_list,
int (*prnt)(const char *fmt, ...))
{
struct lock_list_entry *lle;
int i, nheld;
nheld = 0;
for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
for (i = lle->ll_count - 1; i >= 0; i--) {
witness_list_lock(&lle->ll_children[i], prnt);
nheld++;
}
return (nheld);
}
/*
* This is a bit risky at best. We call this function when we have timed
* out acquiring a spin lock, and we assume that the other CPU is stuck
* with this lock held. So, we go groveling around in the other CPU's
* per-cpu data to try to find the lock instance for this spin lock to
* see when it was last acquired.
*/
void
witness_display_spinlock(struct lock_object *lock, struct thread *owner,
int (*prnt)(const char *fmt, ...))
{
struct lock_instance *instance;
struct pcpu *pc;
if (owner->td_critnest == 0 || owner->td_oncpu == NOCPU)
return;
pc = pcpu_find(owner->td_oncpu);
instance = find_instance(pc->pc_spinlocks, lock);
if (instance != NULL)
witness_list_lock(instance, prnt);
}
void
witness_save(struct lock_object *lock, const char **filep, int *linep)
{
struct lock_list_entry *lock_list;
struct lock_instance *instance;
struct lock_class *class;
/*
* This function is used independently in locking code to deal with
* Giant, SCHEDULER_STOPPED() check can be removed here after Giant
* is gone.
*/
if (SCHEDULER_STOPPED())
return;
KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
return;
class = LOCK_CLASS(lock);
if (class->lc_flags & LC_SLEEPLOCK)
lock_list = curthread->td_sleeplocks;
else {
if (witness_skipspin)
return;
lock_list = PCPU_GET(spinlocks);
}
instance = find_instance(lock_list, lock);
if (instance == NULL) {
kassert_panic("%s: lock (%s) %s not locked", __func__,
class->lc_name, lock->lo_name);
return;
}
*filep = instance->li_file;
*linep = instance->li_line;
}
void
witness_restore(struct lock_object *lock, const char *file, int line)
{
struct lock_list_entry *lock_list;
struct lock_instance *instance;
struct lock_class *class;
/*
* This function is used independently in locking code to deal with
* Giant, SCHEDULER_STOPPED() check can be removed here after Giant
* is gone.
*/
if (SCHEDULER_STOPPED())
return;
KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
return;
class = LOCK_CLASS(lock);
if (class->lc_flags & LC_SLEEPLOCK)
lock_list = curthread->td_sleeplocks;
else {
if (witness_skipspin)
return;
lock_list = PCPU_GET(spinlocks);
}
instance = find_instance(lock_list, lock);
if (instance == NULL)
kassert_panic("%s: lock (%s) %s not locked", __func__,
class->lc_name, lock->lo_name);
lock->lo_witness->w_file = file;
lock->lo_witness->w_line = line;
if (instance == NULL)
return;
instance->li_file = file;
instance->li_line = line;
}
void
witness_assert(const struct lock_object *lock, int flags, const char *file,
int line)
{
#ifdef INVARIANT_SUPPORT
struct lock_instance *instance;
struct lock_class *class;
if (lock->lo_witness == NULL || witness_watch < 1 || panicstr != NULL)
return;
class = LOCK_CLASS(lock);
if ((class->lc_flags & LC_SLEEPLOCK) != 0)
instance = find_instance(curthread->td_sleeplocks, lock);
else if ((class->lc_flags & LC_SPINLOCK) != 0)
instance = find_instance(PCPU_GET(spinlocks), lock);
else {
kassert_panic("Lock (%s) %s is not sleep or spin!",
class->lc_name, lock->lo_name);
return;
}
switch (flags) {
case LA_UNLOCKED:
if (instance != NULL)
kassert_panic("Lock (%s) %s locked @ %s:%d.",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
break;
case LA_LOCKED:
case LA_LOCKED | LA_RECURSED:
case LA_LOCKED | LA_NOTRECURSED:
case LA_SLOCKED:
case LA_SLOCKED | LA_RECURSED:
case LA_SLOCKED | LA_NOTRECURSED:
case LA_XLOCKED:
case LA_XLOCKED | LA_RECURSED:
case LA_XLOCKED | LA_NOTRECURSED:
if (instance == NULL) {
kassert_panic("Lock (%s) %s not locked @ %s:%d.",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
break;
}
if ((flags & LA_XLOCKED) != 0 &&
(instance->li_flags & LI_EXCLUSIVE) == 0)
kassert_panic(
"Lock (%s) %s not exclusively locked @ %s:%d.",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
if ((flags & LA_SLOCKED) != 0 &&
(instance->li_flags & LI_EXCLUSIVE) != 0)
kassert_panic(
"Lock (%s) %s exclusively locked @ %s:%d.",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
if ((flags & LA_RECURSED) != 0 &&
(instance->li_flags & LI_RECURSEMASK) == 0)
kassert_panic("Lock (%s) %s not recursed @ %s:%d.",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
if ((flags & LA_NOTRECURSED) != 0 &&
(instance->li_flags & LI_RECURSEMASK) != 0)
kassert_panic("Lock (%s) %s recursed @ %s:%d.",
class->lc_name, lock->lo_name,
fixup_filename(file), line);
break;
default:
kassert_panic("Invalid lock assertion at %s:%d.",
fixup_filename(file), line);
}
#endif /* INVARIANT_SUPPORT */
}
static void
witness_setflag(struct lock_object *lock, int flag, int set)
{
struct lock_list_entry *lock_list;
struct lock_instance *instance;
struct lock_class *class;
if (lock->lo_witness == NULL || witness_watch == -1 || panicstr != NULL)
return;
class = LOCK_CLASS(lock);
if (class->lc_flags & LC_SLEEPLOCK)
lock_list = curthread->td_sleeplocks;
else {
if (witness_skipspin)
return;
lock_list = PCPU_GET(spinlocks);
}
instance = find_instance(lock_list, lock);
if (instance == NULL) {
kassert_panic("%s: lock (%s) %s not locked", __func__,
class->lc_name, lock->lo_name);
return;
}
if (set)
instance->li_flags |= flag;
else
instance->li_flags &= ~flag;
}
void
witness_norelease(struct lock_object *lock)
{
witness_setflag(lock, LI_NORELEASE, 1);
}
void
witness_releaseok(struct lock_object *lock)
{
witness_setflag(lock, LI_NORELEASE, 0);
}
#ifdef DDB
static void
witness_ddb_list(struct thread *td)
{
KASSERT(witness_cold == 0, ("%s: witness_cold", __func__));
KASSERT(kdb_active, ("%s: not in the debugger", __func__));
if (witness_watch < 1)
return;
witness_list_locks(&td->td_sleeplocks, db_printf);
/*
* We only handle spinlocks if td == curthread. This is somewhat broken
* if td is currently executing on some other CPU and holds spin locks
* as we won't display those locks. If we had a MI way of getting
* the per-cpu data for a given cpu then we could use
* td->td_oncpu to get the list of spinlocks for this thread
* and "fix" this.
*
* That still wouldn't really fix this unless we locked the scheduler
* lock or stopped the other CPU to make sure it wasn't changing the
* list out from under us. It is probably best to just not try to
* handle threads on other CPU's for now.
*/
if (td == curthread && PCPU_GET(spinlocks) != NULL)
witness_list_locks(PCPU_PTR(spinlocks), db_printf);
}
DB_SHOW_COMMAND(locks, db_witness_list)
{
struct thread *td;
if (have_addr)
td = db_lookup_thread(addr, true);
else
td = kdb_thread;
witness_ddb_list(td);
}
DB_SHOW_ALL_COMMAND(locks, db_witness_list_all)
{
struct thread *td;
struct proc *p;
/*
* It would be nice to list only threads and processes that actually
* held sleep locks, but that information is currently not exported
* by WITNESS.
*/
FOREACH_PROC_IN_SYSTEM(p) {
if (!witness_proc_has_locks(p))
continue;
FOREACH_THREAD_IN_PROC(p, td) {
if (!witness_thread_has_locks(td))
continue;
db_printf("Process %d (%s) thread %p (%d)\n", p->p_pid,
p->p_comm, td, td->td_tid);
witness_ddb_list(td);
if (db_pager_quit)
return;
}
}
}
DB_SHOW_ALIAS(alllocks, db_witness_list_all)
DB_SHOW_COMMAND(witness, db_witness_display)
{
witness_ddb_display(db_printf);
}
#endif
static void
sbuf_print_witness_badstacks(struct sbuf *sb, size_t *oldidx)
{
struct witness_lock_order_data *data1, *data2, *tmp_data1, *tmp_data2;
struct witness *tmp_w1, *tmp_w2, *w1, *w2;
int generation, i, j;
tmp_data1 = NULL;
tmp_data2 = NULL;
tmp_w1 = NULL;
tmp_w2 = NULL;
/* Allocate and init temporary storage space. */
tmp_w1 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
tmp_w2 = malloc(sizeof(struct witness), M_TEMP, M_WAITOK | M_ZERO);
tmp_data1 = malloc(sizeof(struct witness_lock_order_data), M_TEMP,
M_WAITOK | M_ZERO);
tmp_data2 = malloc(sizeof(struct witness_lock_order_data), M_TEMP,
M_WAITOK | M_ZERO);
stack_zero(&tmp_data1->wlod_stack);
stack_zero(&tmp_data2->wlod_stack);
restart:
mtx_lock_spin(&w_mtx);
generation = w_generation;
mtx_unlock_spin(&w_mtx);
sbuf_printf(sb, "Number of known direct relationships is %d\n",
w_lohash.wloh_count);
for (i = 1; i < w_max_used_index; i++) {
mtx_lock_spin(&w_mtx);
if (generation != w_generation) {
mtx_unlock_spin(&w_mtx);
/* The graph has changed, try again. */
*oldidx = 0;
sbuf_clear(sb);
goto restart;
}
w1 = &w_data[i];
if (w1->w_reversed == 0) {
mtx_unlock_spin(&w_mtx);
continue;
}
/* Copy w1 locally so we can release the spin lock. */
*tmp_w1 = *w1;
mtx_unlock_spin(&w_mtx);
if (tmp_w1->w_reversed == 0)
continue;
for (j = 1; j < w_max_used_index; j++) {
if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j)
continue;
mtx_lock_spin(&w_mtx);
if (generation != w_generation) {
mtx_unlock_spin(&w_mtx);
/* The graph has changed, try again. */
*oldidx = 0;
sbuf_clear(sb);
goto restart;
}
w2 = &w_data[j];
data1 = witness_lock_order_get(w1, w2);
data2 = witness_lock_order_get(w2, w1);
/*
* Copy information locally so we can release the
* spin lock.
*/
*tmp_w2 = *w2;
if (data1) {
stack_zero(&tmp_data1->wlod_stack);
stack_copy(&data1->wlod_stack,
&tmp_data1->wlod_stack);
}
if (data2 && data2 != data1) {
stack_zero(&tmp_data2->wlod_stack);
stack_copy(&data2->wlod_stack,
&tmp_data2->wlod_stack);
}
mtx_unlock_spin(&w_mtx);
if (blessed(tmp_w1, tmp_w2))
continue;
sbuf_printf(sb,
"\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n",
tmp_w1->w_name, tmp_w1->w_class->lc_name,
tmp_w2->w_name, tmp_w2->w_class->lc_name);
if (data1) {
sbuf_printf(sb,
"Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
tmp_w1->w_name, tmp_w1->w_class->lc_name,
tmp_w2->w_name, tmp_w2->w_class->lc_name);
stack_sbuf_print(sb, &tmp_data1->wlod_stack);
sbuf_printf(sb, "\n");
}
if (data2 && data2 != data1) {
sbuf_printf(sb,
"Lock order \"%s\"(%s) -> \"%s\"(%s) first seen at:\n",
tmp_w2->w_name, tmp_w2->w_class->lc_name,
tmp_w1->w_name, tmp_w1->w_class->lc_name);
stack_sbuf_print(sb, &tmp_data2->wlod_stack);
sbuf_printf(sb, "\n");
}
}
}
mtx_lock_spin(&w_mtx);
if (generation != w_generation) {
mtx_unlock_spin(&w_mtx);
/*
* The graph changed while we were printing stack data,
* try again.
*/
*oldidx = 0;
sbuf_clear(sb);
goto restart;
}
mtx_unlock_spin(&w_mtx);
/* Free temporary storage space. */
free(tmp_data1, M_TEMP);
free(tmp_data2, M_TEMP);
free(tmp_w1, M_TEMP);
free(tmp_w2, M_TEMP);
}
static int
sysctl_debug_witness_badstacks(SYSCTL_HANDLER_ARGS)
{
struct sbuf *sb;
int error;
if (witness_watch < 1) {
error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
return (error);
}
if (witness_cold) {
error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
return (error);
}
error = 0;
sb = sbuf_new(NULL, NULL, badstack_sbuf_size, SBUF_AUTOEXTEND);
if (sb == NULL)
return (ENOMEM);
sbuf_print_witness_badstacks(sb, &req->oldidx);
sbuf_finish(sb);
error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
sbuf_delete(sb);
return (error);
}
#ifdef DDB
static int
sbuf_db_printf_drain(void *arg __unused, const char *data, int len)
{
return (db_printf("%.*s", len, data));
}
DB_SHOW_COMMAND(badstacks, db_witness_badstacks)
{
struct sbuf sb;
char buffer[128];
size_t dummy;
sbuf_new(&sb, buffer, sizeof(buffer), SBUF_FIXEDLEN);
sbuf_set_drain(&sb, sbuf_db_printf_drain, NULL);
sbuf_print_witness_badstacks(&sb, &dummy);
sbuf_finish(&sb);
}
#endif
static int
sysctl_debug_witness_channel(SYSCTL_HANDLER_ARGS)
{
static const struct {
enum witness_channel channel;
const char *name;
} channels[] = {
{ WITNESS_CONSOLE, "console" },
{ WITNESS_LOG, "log" },
{ WITNESS_NONE, "none" },
};
char buf[16];
u_int i;
int error;
buf[0] = '\0';
for (i = 0; i < nitems(channels); i++)
if (witness_channel == channels[i].channel) {
snprintf(buf, sizeof(buf), "%s", channels[i].name);
break;
}
error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
if (error != 0 || req->newptr == NULL)
return (error);
error = EINVAL;
for (i = 0; i < nitems(channels); i++)
if (strcmp(channels[i].name, buf) == 0) {
witness_channel = channels[i].channel;
error = 0;
break;
}
return (error);
}
static int
sysctl_debug_witness_fullgraph(SYSCTL_HANDLER_ARGS)
{
struct witness *w;
struct sbuf *sb;
int error;
#ifdef __i386__
error = SYSCTL_OUT(req, w_notallowed, sizeof(w_notallowed));
return (error);
#endif
if (witness_watch < 1) {
error = SYSCTL_OUT(req, w_notrunning, sizeof(w_notrunning));
return (error);
}
if (witness_cold) {
error = SYSCTL_OUT(req, w_stillcold, sizeof(w_stillcold));
return (error);
}
error = 0;
error = sysctl_wire_old_buffer(req, 0);
if (error != 0)
return (error);
sb = sbuf_new_for_sysctl(NULL, NULL, FULLGRAPH_SBUF_SIZE, req);
if (sb == NULL)
return (ENOMEM);
sbuf_printf(sb, "\n");
mtx_lock_spin(&w_mtx);
STAILQ_FOREACH(w, &w_all, w_list)
w->w_displayed = 0;
STAILQ_FOREACH(w, &w_all, w_list)
witness_add_fullgraph(sb, w);
mtx_unlock_spin(&w_mtx);
/*
* Close the sbuf and return to userland.
*/
error = sbuf_finish(sb);
sbuf_delete(sb);
return (error);
}
static int
sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
{
int error, value;
value = witness_watch;
error = sysctl_handle_int(oidp, &value, 0, req);
if (error != 0 || req->newptr == NULL)
return (error);
if (value > 1 || value < -1 ||
(witness_watch == -1 && value != witness_watch))
return (EINVAL);
witness_watch = value;
return (0);
}
static void
witness_add_fullgraph(struct sbuf *sb, struct witness *w)
{
int i;
if (w->w_displayed != 0 || (w->w_file == NULL && w->w_line == 0))
return;
w->w_displayed = 1;
WITNESS_INDEX_ASSERT(w->w_index);
for (i = 1; i <= w_max_used_index; i++) {
if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) {
sbuf_printf(sb, "\"%s\",\"%s\"\n", w->w_name,
w_data[i].w_name);
witness_add_fullgraph(sb, &w_data[i]);
}
}
}
/*
* A simple hash function. Takes a key pointer and a key size. If size == 0,
* interprets the key as a string and reads until the null
* terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit
* hash value computed from the key.
*/
static uint32_t
witness_hash_djb2(const uint8_t *key, uint32_t size)
{
unsigned int hash = 5381;
int i;
/* hash = hash * 33 + key[i] */
if (size)
for (i = 0; i < size; i++)
hash = ((hash << 5) + hash) + (unsigned int)key[i];
else
for (i = 0; key[i] != 0; i++)
hash = ((hash << 5) + hash) + (unsigned int)key[i];
return (hash);
}
/*
* Initializes the two witness hash tables. Called exactly once from
* witness_initialize().
*/
static void
witness_init_hash_tables(void)
{
int i;
MPASS(witness_cold);
/* Initialize the hash tables. */
for (i = 0; i < WITNESS_HASH_SIZE; i++)
w_hash.wh_array[i] = NULL;
w_hash.wh_size = WITNESS_HASH_SIZE;
w_hash.wh_count = 0;
/* Initialize the lock order data hash. */
w_lofree = NULL;
for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) {
memset(&w_lodata[i], 0, sizeof(w_lodata[i]));
w_lodata[i].wlod_next = w_lofree;
w_lofree = &w_lodata[i];
}
w_lohash.wloh_size = WITNESS_LO_HASH_SIZE;
w_lohash.wloh_count = 0;
for (i = 0; i < WITNESS_LO_HASH_SIZE; i++)
w_lohash.wloh_array[i] = NULL;
}
static struct witness *
witness_hash_get(const char *key)
{
struct witness *w;
uint32_t hash;
MPASS(key != NULL);
if (witness_cold == 0)
mtx_assert(&w_mtx, MA_OWNED);
hash = witness_hash_djb2(key, 0) % w_hash.wh_size;
w = w_hash.wh_array[hash];
while (w != NULL) {
if (strcmp(w->w_name, key) == 0)
goto out;
w = w->w_hash_next;
}
out:
return (w);
}
static void
witness_hash_put(struct witness *w)
{
uint32_t hash;
MPASS(w != NULL);
MPASS(w->w_name != NULL);
if (witness_cold == 0)
mtx_assert(&w_mtx, MA_OWNED);
KASSERT(witness_hash_get(w->w_name) == NULL,
("%s: trying to add a hash entry that already exists!", __func__));
KASSERT(w->w_hash_next == NULL,
("%s: w->w_hash_next != NULL", __func__));
hash = witness_hash_djb2(w->w_name, 0) % w_hash.wh_size;
w->w_hash_next = w_hash.wh_array[hash];
w_hash.wh_array[hash] = w;
w_hash.wh_count++;
}
static struct witness_lock_order_data *
witness_lock_order_get(struct witness *parent, struct witness *child)
{
struct witness_lock_order_data *data = NULL;
struct witness_lock_order_key key;
unsigned int hash;
MPASS(parent != NULL && child != NULL);
key.from = parent->w_index;
key.to = child->w_index;
WITNESS_INDEX_ASSERT(key.from);
WITNESS_INDEX_ASSERT(key.to);
if ((w_rmatrix[parent->w_index][child->w_index]
& WITNESS_LOCK_ORDER_KNOWN) == 0)
goto out;
hash = witness_hash_djb2((const char*)&key,
sizeof(key)) % w_lohash.wloh_size;
data = w_lohash.wloh_array[hash];
while (data != NULL) {
if (witness_lock_order_key_equal(&data->wlod_key, &key))
break;
data = data->wlod_next;
}
out:
return (data);
}
/*
* Verify that parent and child have a known relationship, are not the same,
* and child is actually a child of parent. This is done without w_mtx
* to avoid contention in the common case.
*/
static int
witness_lock_order_check(struct witness *parent, struct witness *child)
{
if (parent != child &&
w_rmatrix[parent->w_index][child->w_index]
& WITNESS_LOCK_ORDER_KNOWN &&
isitmychild(parent, child))
return (1);
return (0);
}
static int
witness_lock_order_add(struct witness *parent, struct witness *child)
{
struct witness_lock_order_data *data = NULL;
struct witness_lock_order_key key;
unsigned int hash;
MPASS(parent != NULL && child != NULL);
key.from = parent->w_index;
key.to = child->w_index;
WITNESS_INDEX_ASSERT(key.from);
WITNESS_INDEX_ASSERT(key.to);
if (w_rmatrix[parent->w_index][child->w_index]
& WITNESS_LOCK_ORDER_KNOWN)
return (1);
hash = witness_hash_djb2((const char*)&key,
sizeof(key)) % w_lohash.wloh_size;
w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN;
data = w_lofree;
if (data == NULL)
return (0);
w_lofree = data->wlod_next;
data->wlod_next = w_lohash.wloh_array[hash];
data->wlod_key = key;
w_lohash.wloh_array[hash] = data;
w_lohash.wloh_count++;
stack_zero(&data->wlod_stack);
stack_save(&data->wlod_stack);
return (1);
}
/* Call this whenever the structure of the witness graph changes. */
static void
witness_increment_graph_generation(void)
{
if (witness_cold == 0)
mtx_assert(&w_mtx, MA_OWNED);
w_generation++;
}
static int
witness_output_drain(void *arg __unused, const char *data, int len)
{
witness_output("%.*s", len, data);
return (len);
}
static void
witness_debugger(int cond, const char *msg)
{
char buf[32];
struct sbuf sb;
struct stack st;
if (!cond)
return;
if (witness_trace) {
sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
sbuf_set_drain(&sb, witness_output_drain, NULL);
stack_zero(&st);
stack_save(&st);
witness_output("stack backtrace:\n");
stack_sbuf_print_ddb(&sb, &st);
sbuf_finish(&sb);
}
#ifdef KDB
if (witness_kdb)
kdb_enter(KDB_WHY_WITNESS, msg);
#endif
}
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