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freebsd-skq/sys/kern/subr_witness.c
attilio f7f31164f1 - Embed the recursion counter for any locking primitive directly in the 
lock_object, using an unified field called lo_data.
- Replace lo_type usage with the w_name usage and at init time pass the
  lock "type" directly to witness_init() from the parent lock init
  function.  Handle delayed initialization before than
  witness_initialize() is called through the witness_pendhelp structure.
- Axe out LO_ENROLLPEND as it is not really needed.  The case where the
  mutex init delayed wants to be destroyed can't happen because
  witness_destroy() checks for witness_cold and panic in case.
- In enroll(), if we cannot allocate a new object from the freelist,
  notify that to userspace through a printf().
- Modify the depart function in order to return nothing as in the current
  CVS version it always returns true and adjust callers accordingly.
- Fix the witness_addgraph() argument name prototype.
- Remove unuseful code from itismychild().

This commit leads to a shrinked struct lock_object and so smaller locks,
in particular on amd64 where 2 uintptr_t (16 bytes per-primitive) are
gained.

Reviewed by:	jhb
2008-05-15 20:10:06 +00:00

2095 lines
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/*-
* 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_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/sysctl.h>
#include <sys/systm.h>
#include <ddb/ddb.h>
#include <machine/stdarg.h>
/* 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 this to check for blessed mutexes */
#undef BLESSING
#define WITNESS_COUNT 1024
#define WITNESS_CHILDCOUNT (WITNESS_COUNT * 4)
#define WITNESS_SBUFSIZE 32768
#define WITNESS_PENDLIST 512
/*
* XXX: This is somewhat bogus, as we assume here that at most 1024 threads
* will hold LOCK_NCHILDREN * 2 locks. We handle failure ok, and we should
* probably be safe for the most part, but it's still a SWAG.
*/
#define LOCK_CHILDCOUNT (MAXCPU + 1024) * 2
#define WITNESS_NCHILDREN 6
#define LOCK_NCHILDREN 3
struct witness_child_list_entry;
/*
* 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; /* Recursion count and 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;
};
struct witness {
const char *w_name;
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_child_list_entry *w_children; /* Great evilness... */
const char *w_file;
int w_line;
u_int w_level;
u_int w_refcount;
u_char w_Giant_squawked:1;
u_char w_other_squawked:1;
u_char w_same_squawked:1;
u_char w_displayed:1;
};
struct witness_child_list_entry {
struct witness_child_list_entry *wcl_next;
struct witness *wcl_children[WITNESS_NCHILDREN];
u_int wcl_count;
};
STAILQ_HEAD(witness_list, witness);
#ifdef BLESSING
struct witness_blessed {
const char *b_lock1;
const char *b_lock2;
};
#endif
struct witness_order_list_entry {
const char *w_name;
struct lock_class *w_class;
};
struct witness_pendhelp {
const char *wh_type;
struct lock_object *wh_lock;
};
#ifdef BLESSING
static int blessed(struct witness *, struct witness *);
#endif
static void depart(struct witness *w);
static struct witness *enroll(const char *description,
struct lock_class *lock_class);
static int insertchild(struct witness *parent, struct witness *child);
static int isitmychild(struct witness *parent, struct witness *child);
static int isitmydescendant(struct witness *parent, struct witness *child);
static int itismychild(struct witness *parent, struct witness *child);
static void removechild(struct witness *parent, struct witness *child);
static int sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS);
static int sysctl_debug_witness_graphs(SYSCTL_HANDLER_ARGS);
static const char *fixup_filename(const char *file);
static void witness_addgraph(struct sbuf *sb, struct witness *parent);
static struct witness *witness_get(void);
static void witness_free(struct witness *m);
static struct witness_child_list_entry *witness_child_get(void);
static void witness_child_free(struct witness_child_list_entry *wcl);
static struct lock_list_entry *witness_lock_list_get(void);
static void witness_lock_list_free(struct lock_list_entry *lle);
static struct lock_instance *find_instance(struct lock_list_entry *lock_list,
struct lock_object *lock);
static void witness_list_lock(struct lock_instance *instance);
#ifdef DDB
static void witness_leveldescendents(struct witness *parent, int level);
static void witness_levelall(void);
static void witness_displaydescendants(void(*)(const char *fmt, ...),
struct witness *, int indent);
static void witness_display_list(void(*prnt)(const char *fmt, ...),
struct witness_list *list);
static void witness_display(void(*)(const char *fmt, ...));
static void witness_list(struct thread *td);
#endif
SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW, 0, "Witness Locking");
/*
* If set to 0, witness is disabled. If set to a non-zero value, witness
* performs full lock order checking for all locks. At runtime, this
* value may be set to 0 to turn off witness. witness is not allowed be
* turned on once it is turned off, however.
*/
static int witness_watch = 1;
TUNABLE_INT("debug.witness.watch", &witness_watch);
SYSCTL_PROC(_debug_witness, OID_AUTO, watch, CTLFLAG_RW | CTLTYPE_INT, NULL, 0,
sysctl_debug_witness_watch, "I", "witness is watching lock operations");
SYSCTL_PROC(_debug_witness, OID_AUTO, graphs, CTLTYPE_STRING | CTLFLAG_RD,
NULL, 0, sysctl_debug_witness_graphs, "A", "Show locks relation graphs");
#ifdef KDB
/*
* When KDB is enabled and witness_kdb is set to 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
TUNABLE_INT("debug.witness.kdb", &witness_kdb);
SYSCTL_INT(_debug_witness, OID_AUTO, kdb, CTLFLAG_RW, &witness_kdb, 0, "");
/*
* When KDB is enabled and witness_trace is set to 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;
TUNABLE_INT("debug.witness.trace", &witness_trace);
SYSCTL_INT(_debug_witness, OID_AUTO, trace, CTLFLAG_RW, &witness_trace, 0, "");
#endif /* KDB */
#ifdef WITNESS_SKIPSPIN
int witness_skipspin = 1;
#else
int witness_skipspin = 0;
#endif
TUNABLE_INT("debug.witness.skipspin", &witness_skipspin);
SYSCTL_INT(_debug_witness, OID_AUTO, skipspin, CTLFLAG_RDTUN,
&witness_skipspin, 0, "");
static struct mtx w_mtx;
static struct witness_list w_free = STAILQ_HEAD_INITIALIZER(w_free);
static struct witness_list w_all = STAILQ_HEAD_INITIALIZER(w_all);
static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin);
static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep);
static struct witness_child_list_entry *w_child_free = NULL;
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, w_child_free_cnt, w_child_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,
"");
SYSCTL_INT(_debug_witness, OID_AUTO, child_free_cnt, CTLFLAG_RD,
&w_child_free_cnt, 0, "");
SYSCTL_INT(_debug_witness, OID_AUTO, child_cnt, CTLFLAG_RD, &w_child_cnt, 0,
"");
static struct witness w_data[WITNESS_COUNT];
static struct witness_child_list_entry w_childdata[WITNESS_CHILDCOUNT];
static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
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 },
{ "process lock", &lock_class_mtx_sleep },
{ "session", &lock_class_mtx_sleep },
{ "uidinfo hash", &lock_class_rw },
#ifdef HWPMC_HOOKS
{ "pmc-sleep", &lock_class_mtx_sleep },
#endif
{ 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_mtx_sleep },
{ "rtentry", &lock_class_mtx_sleep },
{ "ifaddr", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* Multicast - protocol locks before interface locks, after UDP locks.
*/
{ "udpinp", &lock_class_rw },
{ "in_multi_mtx", &lock_class_mtx_sleep },
{ "igmp_mtx", &lock_class_mtx_sleep },
{ "if_addr_mtx", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* UNIX Domain Sockets
*/
{ "unp", &lock_class_mtx_sleep },
{ "so_snd", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* UDP/IP
*/
{ "udp", &lock_class_rw },
{ "udpinp", &lock_class_rw },
{ "so_snd", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* TCP/IP
*/
{ "tcp", &lock_class_rw },
{ "tcpinp", &lock_class_rw },
{ "so_snd", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* SLIP
*/
{ "slip_mtx", &lock_class_mtx_sleep },
{ "slip sc_mtx", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* netatalk
*/
{ "ddp_list_mtx", &lock_class_mtx_sleep },
{ "ddp_mtx", &lock_class_mtx_sleep },
{ NULL, NULL },
/*
* BPF
*/
{ "bpf global lock", &lock_class_mtx_sleep },
{ "bpf interface lock", &lock_class_mtx_sleep },
{ "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
*/
{ "system map", &lock_class_mtx_sleep },
{ "vm page queue mutex", &lock_class_mtx_sleep },
{ "vnode interlock", &lock_class_mtx_sleep },
{ "cdev", &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 },
/*
* spin locks
*/
#ifdef SMP
{ "ap boot", &lock_class_mtx_spin },
#endif
{ "rm.mutex_mtx", &lock_class_mtx_spin },
{ "sio", &lock_class_mtx_spin },
{ "scrlock", &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 },
#ifdef HWPMC_HOOKS
{ "pmc-per-proc", &lock_class_mtx_spin },
#endif
{ "process slock", &lock_class_mtx_spin },
{ "sleepq chain", &lock_class_mtx_spin },
{ "umtx lock", &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 },
{ "syscons video lock", &lock_class_mtx_spin },
{ "time lock", &lock_class_mtx_spin },
#ifdef SMP
{ "smp rendezvous", &lock_class_mtx_spin },
#endif
#ifdef __powerpc__
{ "tlb0", &lock_class_mtx_spin },
#endif
/*
* 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 },
#ifdef __ia64__
{ "MCA spin lock", &lock_class_mtx_spin },
#endif
#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 }
};
#ifdef BLESSING
/*
* Pairs of locks which have been blessed
* Don't complain about order problems with blessed locks
*/
static struct witness_blessed blessed_list[] = {
};
static int blessed_count =
sizeof(blessed_list) / sizeof(struct witness_blessed);
#endif
/*
* 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;
/*
* 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.
*/
static void
witness_initialize(void *dummy __unused)
{
struct lock_object *lock;
struct witness_order_list_entry *order;
struct witness *w, *w1;
int i;
/*
* 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 = 0; i < WITNESS_COUNT; i++)
witness_free(&w_data[i]);
for (i = 0; i < WITNESS_CHILDCOUNT; i++)
witness_child_free(&w_childdata[i]);
for (i = 0; i < LOCK_CHILDCOUNT; i++)
witness_lock_list_free(&w_locklistdata[i]);
/* 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";
if (!itismychild(w, w1))
panic("Not enough memory for static orders!");
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);
}
SYSINIT(witness_init, SI_SUB_WITNESS, SI_ORDER_FIRST, witness_initialize,
NULL);
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 == witness_watch)
return (0);
if (value != 0)
return (EINVAL);
witness_watch = 0;
return (0);
}
static int
sysctl_debug_witness_graphs(SYSCTL_HANDLER_ARGS)
{
struct witness *w;
struct sbuf *sb;
int error;
KASSERT(witness_cold == 0, ("%s: witness is still cold", __func__));
sb = sbuf_new(NULL, NULL, WITNESS_SBUFSIZE, SBUF_FIXEDLEN);
if (sb == NULL)
return (ENOMEM);
mtx_lock_spin(&w_mtx);
STAILQ_FOREACH(w, &w_all, w_list)
w->w_displayed = 0;
STAILQ_FOREACH(w, &w_all, w_list)
witness_addgraph(sb, w);
mtx_unlock_spin(&w_mtx);
if (sbuf_overflowed(sb)) {
sbuf_delete(sb);
panic("%s: sbuf overflowed, bump the static buffer size\n",
__func__);
}
sbuf_finish(sb);
error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
sbuf_delete(sb);
return (error);
}
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)
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)
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)
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 == 0 || 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, bump it\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) && lock->lo_witness != NULL) {
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_levelall (void)
{
struct witness_list *list;
struct witness *w, *w1;
/*
* First clear all levels.
*/
STAILQ_FOREACH(w, &w_all, w_list) {
w->w_level = 0;
}
/*
* Look for locks with no parent and level all their descendants.
*/
STAILQ_FOREACH(w, &w_all, w_list) {
/*
* This is just an optimization, technically we could get
* away just walking the all list each time.
*/
if (w->w_class->lc_flags & LC_SLEEPLOCK)
list = &w_sleep;
else
list = &w_spin;
STAILQ_FOREACH(w1, list, w_typelist) {
if (isitmychild(w1, w))
goto skip;
}
witness_leveldescendents(w, 0);
skip:
; /* silence GCC 3.x */
}
}
static void
witness_leveldescendents(struct witness *parent, int level)
{
struct witness_child_list_entry *wcl;
int i;
if (parent->w_level < level)
parent->w_level = level;
level++;
for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next)
for (i = 0; i < wcl->wcl_count; i++)
witness_leveldescendents(wcl->wcl_children[i], level);
}
static void
witness_displaydescendants(void(*prnt)(const char *fmt, ...),
struct witness *parent, int indent)
{
struct witness_child_list_entry *wcl;
int i, level;
level = parent->w_level;
prnt("%-2d", level);
for (i = 0; i < indent; i++)
prnt(" ");
if (parent->w_refcount > 0)
prnt("%s", parent->w_name);
else
prnt("(dead)");
if (parent->w_displayed) {
prnt(" -- (already displayed)\n");
return;
}
parent->w_displayed = 1;
if (parent->w_refcount > 0) {
if (parent->w_file != NULL)
prnt(" -- last acquired @ %s:%d", parent->w_file,
parent->w_line);
}
prnt("\n");
for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next)
for (i = 0; i < wcl->wcl_count; i++)
witness_displaydescendants(prnt,
wcl->wcl_children[i], indent + 1);
}
static void
witness_display_list(void(*prnt)(const char *fmt, ...),
struct witness_list *list)
{
struct witness *w;
STAILQ_FOREACH(w, list, w_typelist) {
if (w->w_file == NULL || w->w_level > 0)
continue;
/*
* This lock has no anscestors, display its descendants.
*/
witness_displaydescendants(prnt, w, 0);
}
}
static void
witness_addgraph(struct sbuf *sb, struct witness *parent)
{
struct witness_child_list_entry *wcl;
int i;
if (parent->w_displayed != 0 || parent->w_refcount == 0 ||
parent->w_file == NULL)
return;
parent->w_displayed = 1;
for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next)
for (i = 0; i < wcl->wcl_count; i++) {
sbuf_printf(sb, "\"%s\",\"%s\"\n", parent->w_name,
wcl->wcl_children[i]->w_name);
witness_addgraph(sb, wcl->wcl_children[i]);
}
}
static void
witness_display(void(*prnt)(const char *fmt, ...))
{
struct witness *w;
KASSERT(!witness_cold, ("%s: witness_cold", __func__));
witness_levelall();
/* 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_display_list(prnt, &w_sleep);
/*
* Now do spin locks which have been acquired at least once.
*/
prnt("\nSpin locks:\n");
witness_display_list(prnt, &w_spin);
/*
* 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\n", w->w_name);
}
}
#endif /* DDB */
/* 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);
}
int
witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
{
if (witness_watch == 0 || 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);
MPASS(!mtx_owned(&w_mtx));
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 (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);
if (!itismychild(lock1->lo_witness, lock2->lo_witness))
return (ENOMEM);
mtx_unlock_spin(&w_mtx);
return (0);
}
void
witness_checkorder(struct lock_object *lock, int flags, const char *file,
int line)
{
struct lock_list_entry **lock_list, *lle;
struct lock_instance *lock1, *lock2;
struct lock_class *class;
struct witness *w, *w1;
struct thread *td;
int i, j;
if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL ||
panicstr != NULL)
return;
/*
* Try locks do not block if they fail to acquire the lock, thus
* there is no danger of deadlocks or of switching while holding a
* spin lock if we acquire a lock via a try operation. This
* function shouldn't even be called for try locks, so panic if
* that happens.
*/
if (flags & LOP_TRYLOCK)
panic("%s should not be called for try lock operations",
__func__);
w = lock->lo_witness;
class = LOCK_CLASS(lock);
td = curthread;
file = fixup_filename(file);
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)
panic("blockable sleep lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name, file, line);
/*
* If this is the first lock acquired then just return as
* no order checking is needed.
*/
if (td->td_sleeplocks == NULL)
return;
lock_list = &td->td_sleeplocks;
} else {
/*
* If this is the first lock, just return as no order
* checking is needed. We check this in both if clauses
* here as unifying the check would require us to use a
* critical section to ensure we don't migrate while doing
* the check. Note that if this is not the first lock, we
* are already in a critical section and are safe for the
* rest of the check.
*/
if (PCPU_GET(spinlocks) == NULL)
return;
lock_list = PCPU_PTR(spinlocks);
}
/*
* 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) {
printf("shared lock of (%s) %s @ %s:%d\n",
class->lc_name, lock->lo_name, file, line);
printf("while exclusively locked from %s:%d\n",
lock1->li_file, lock1->li_line);
panic("share->excl");
}
if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
(flags & LOP_EXCLUSIVE) != 0) {
printf("exclusive lock of (%s) %s @ %s:%d\n",
class->lc_name, lock->lo_name, file, line);
printf("while share locked from %s:%d\n",
lock1->li_file, lock1->li_line);
panic("excl->share");
}
return;
}
/*
* 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.
*/
lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1];
w1 = lock1->li_lock->lo_witness;
if (w1 == w) {
if (w->w_same_squawked || (lock->lo_flags & LO_DUPOK) ||
(flags & LOP_DUPOK))
return;
w->w_same_squawked = 1;
printf("acquiring duplicate lock of same type: \"%s\"\n",
w->w_name);
printf(" 1st %s @ %s:%d\n", lock1->li_lock->lo_name,
lock1->li_file, lock1->li_line);
printf(" 2nd %s @ %s:%d\n", lock->lo_name, file, line);
#ifdef KDB
goto debugger;
#else
return;
#endif
}
MPASS(!mtx_owned(&w_mtx));
mtx_lock_spin(&w_mtx);
/*
* If we know that the 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)) {
mtx_unlock_spin(&w_mtx);
return;
}
for (j = 0, lle = *lock_list; lle != NULL; lle = lle->ll_next) {
for (i = lle->ll_count - 1; i >= 0; i--, j++) {
MPASS(j < WITNESS_COUNT);
lock1 = &lle->ll_children[i];
w1 = lock1->li_lock->lo_witness;
/*
* If this lock doesn't undergo witness checking,
* then skip it.
*/
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_lock->lo_flags & LO_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 &&
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 &&
(lock1->li_lock->lo_flags & LO_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_lock->lo_flags & LO_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.
*/
mtx_unlock_spin(&w_mtx);
#ifdef BLESSING
/*
* If the lock order is blessed, just bail. We don't
* look for other lock order violations though, which
* may be a bug.
*/
if (blessed(w, w1))
return;
#endif
if (lock1->li_lock == &Giant.lock_object) {
if (w1->w_Giant_squawked)
return;
else
w1->w_Giant_squawked = 1;
} else {
if (w1->w_other_squawked)
return;
else
w1->w_other_squawked = 1;
}
/*
* Ok, yell about it.
*/
if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
(lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
printf(
"lock order reversal: (sleepable after non-sleepable)\n");
else if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0
&& lock == &Giant.lock_object)
printf(
"lock order reversal: (Giant after non-sleepable)\n");
else
printf("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) {
printf(" 1st %p %s (%s) @ %s:%d\n",
lock1->li_lock, lock1->li_lock->lo_name,
w1->w_name, lock1->li_file, lock1->li_line);
printf(" 2nd %p %s (%s) @ %s:%d\n", lock,
lock->lo_name, w->w_name, file, line);
} else {
printf(" 1st %p %s (%s) @ %s:%d\n",
lock2->li_lock, lock2->li_lock->lo_name,
lock2->li_lock->lo_witness->w_name,
lock2->li_file, lock2->li_line);
printf(" 2nd %p %s (%s) @ %s:%d\n",
lock1->li_lock, lock1->li_lock->lo_name,
w1->w_name, lock1->li_file, lock1->li_line);
printf(" 3rd %p %s (%s) @ %s:%d\n", lock,
lock->lo_name, w->w_name, file, line);
}
#ifdef KDB
goto debugger;
#else
return;
#endif
}
}
lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1];
/*
* 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 &&
!(lock1->li_lock == &Giant.lock_object &&
(lock->lo_flags & LO_SLEEPABLE) != 0)) {
CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
w->w_name, lock1->li_lock->lo_witness->w_name);
if (!itismychild(lock1->li_lock->lo_witness, w))
/* Witness is dead. */
return;
}
mtx_unlock_spin(&w_mtx);
return;
#ifdef KDB
debugger:
if (witness_trace)
kdb_backtrace();
if (witness_kdb)
kdb_enter(KDB_WHY_WITNESS, __func__);
#endif
}
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 == 0 || lock->lo_witness == NULL ||
panicstr != NULL)
return;
w = lock->lo_witness;
td = curthread;
file = fixup_filename(file);
/* 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;
if ((flags & LOP_EXCLUSIVE) != 0)
instance->li_flags = LI_EXCLUSIVE;
else
instance->li_flags = 0;
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, ("%s: witness_cold", __func__));
if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
return;
class = LOCK_CLASS(lock);
file = fixup_filename(file);
if ((lock->lo_flags & LO_UPGRADABLE) == 0)
panic("upgrade of non-upgradable lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name, file, line);
if ((class->lc_flags & LC_SLEEPLOCK) == 0)
panic("upgrade of non-sleep lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name, file, line);
instance = find_instance(curthread->td_sleeplocks, lock);
if (instance == NULL)
panic("upgrade of unlocked lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name, file, line);
if ((instance->li_flags & LI_EXCLUSIVE) != 0)
panic("upgrade of exclusive lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name, file, line);
if ((instance->li_flags & LI_RECURSEMASK) != 0)
panic("upgrade of recursed lock (%s) %s r=%d @ %s:%d",
class->lc_name, lock->lo_name,
instance->li_flags & LI_RECURSEMASK, 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, ("%s: witness_cold", __func__));
if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
return;
class = LOCK_CLASS(lock);
file = fixup_filename(file);
if ((lock->lo_flags & LO_UPGRADABLE) == 0)
panic("downgrade of non-upgradable lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name, file, line);
if ((class->lc_flags & LC_SLEEPLOCK) == 0)
panic("downgrade of non-sleep lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name, file, line);
instance = find_instance(curthread->td_sleeplocks, lock);
if (instance == NULL)
panic("downgrade of unlocked lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name, file, line);
if ((instance->li_flags & LI_EXCLUSIVE) == 0)
panic("downgrade of shared lock (%s) %s @ %s:%d",
class->lc_name, lock->lo_name, file, line);
if ((instance->li_flags & LI_RECURSEMASK) != 0)
panic("downgrade of recursed lock (%s) %s r=%d @ %s:%d",
class->lc_name, lock->lo_name,
instance->li_flags & LI_RECURSEMASK, 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 || witness_watch == 0 || lock->lo_witness == NULL ||
panicstr != NULL)
return;
td = curthread;
class = LOCK_CLASS(lock);
file = fixup_filename(file);
/* Find lock instance associated with this lock. */
if (class->lc_flags & LC_SLEEPLOCK)
lock_list = &td->td_sleeplocks;
else
lock_list = PCPU_PTR(spinlocks);
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;
}
panic("lock (%s) %s not locked @ %s:%d", class->lc_name, lock->lo_name,
file, line);
found:
/* First, check for shared/exclusive mismatches. */
if ((instance->li_flags & LI_EXCLUSIVE) != 0 &&
(flags & LOP_EXCLUSIVE) == 0) {
printf("shared unlock of (%s) %s @ %s:%d\n", class->lc_name,
lock->lo_name, file, line);
printf("while exclusively locked from %s:%d\n",
instance->li_file, instance->li_line);
panic("excl->ushare");
}
if ((instance->li_flags & LI_EXCLUSIVE) == 0 &&
(flags & LOP_EXCLUSIVE) != 0) {
printf("exclusive unlock of (%s) %s @ %s:%d\n", class->lc_name,
lock->lo_name, file, line);
printf("while share locked from %s:%d\n", instance->li_file,
instance->li_line);
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;
}
/* 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);
/* If this lock list entry is now empty, free it. */
if ((*lock_list)->ll_count == 0) {
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);
}
}
/*
* 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
* console 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 *lle;
struct lock_instance *lock1;
struct thread *td;
va_list ap;
int i, n;
if (witness_cold || witness_watch == 0 || 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_lock->lo_flags & LO_SLEEPABLE) != 0)
continue;
if (n == 0) {
va_start(ap, fmt);
vprintf(fmt, ap);
va_end(ap);
printf(" with the following");
if (flags & WARN_SLEEPOK)
printf(" non-sleepable");
printf(" locks held:\n");
}
n++;
witness_list_lock(lock1);
}
if (PCPU_GET(spinlocks) != NULL) {
/*
* Since we already hold a spinlock preemption is
* already blocked.
*/
if (n == 0) {
va_start(ap, fmt);
vprintf(fmt, ap);
va_end(ap);
printf(" with the following");
if (flags & WARN_SLEEPOK)
printf(" non-sleepable");
printf(" locks held:\n");
}
n += witness_list_locks(PCPU_PTR(spinlocks));
}
if (flags & WARN_PANIC && n)
panic("witness_warn");
#ifdef KDB
else if (witness_kdb && n)
kdb_enter(KDB_WHY_WITNESS, __func__);
else if (witness_trace && n)
kdb_backtrace();
#endif
return (n);
}
const char *
witness_file(struct lock_object *lock)
{
struct witness *w;
if (witness_cold || witness_watch == 0 || 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 == 0 || 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;
if (witness_watch == 0 || panicstr != NULL)
return (NULL);
if ((lock_class->lc_flags & LC_SPINLOCK) && witness_skipspin)
return (NULL);
mtx_lock_spin(&w_mtx);
STAILQ_FOREACH(w, &w_all, w_list) {
if (w->w_name == description || (w->w_refcount > 0 &&
strcmp(description, w->w_name) == 0)) {
w->w_refcount++;
mtx_unlock_spin(&w_mtx);
if (lock_class != w->w_class)
panic(
"lock (%s) %s does not match earlier (%s) lock",
description, lock_class->lc_name,
w->w_class->lc_name);
return (w);
}
}
if ((w = witness_get()) == NULL) {
printf("WITNESS: unable to allocate a new witness object\n");
goto out;
}
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++;
} else {
mtx_unlock_spin(&w_mtx);
panic("lock class %s is not sleep or spin",
lock_class->lc_name);
}
mtx_unlock_spin(&w_mtx);
out:
/*
* We issue a warning for any spin locks not defined in the static
* order list as a way to discourage their use (folks should really
* be using non-spin mutexes most of the time). However, several
* 3rd part device drivers use spin locks because that is all they
* have available on Windows and Linux and they think that normal
* mutexes are insufficient.
*/
if ((lock_class->lc_flags & LC_SPINLOCK) && witness_spin_warn)
printf("WITNESS: spin lock %s not in order list\n",
description);
return (w);
}
/* Don't let the door bang you on the way out... */
static void
depart(struct witness *w)
{
struct witness_child_list_entry *wcl, *nwcl;
struct witness_list *list;
struct witness *parent;
MPASS(w->w_refcount == 0);
if (w->w_class->lc_flags & LC_SLEEPLOCK) {
list = &w_sleep;
w_sleep_cnt--;
} else {
list = &w_spin;
w_spin_cnt--;
}
/*
* First, we run through the entire tree looking for any
* witnesses that the outgoing witness is a child of. For
* each parent that we find, we reparent all the direct
* children of the outgoing witness to its parent.
*/
STAILQ_FOREACH(parent, list, w_typelist) {
if (!isitmychild(parent, w))
continue;
removechild(parent, w);
}
/*
* Now we go through and free up the child list of the
* outgoing witness.
*/
for (wcl = w->w_children; wcl != NULL; wcl = nwcl) {
nwcl = wcl->wcl_next;
w_child_cnt--;
witness_child_free(wcl);
}
/*
* Detach from various lists and free.
*/
STAILQ_REMOVE(list, w, witness, w_typelist);
STAILQ_REMOVE(&w_all, w, witness, w_list);
witness_free(w);
}
/*
* Add "child" as a direct child of "parent". Returns false if
* we fail due to out of memory.
*/
static int
insertchild(struct witness *parent, struct witness *child)
{
struct witness_child_list_entry **wcl;
MPASS(child != NULL && parent != NULL);
/*
* Insert "child" after "parent"
*/
wcl = &parent->w_children;
while (*wcl != NULL && (*wcl)->wcl_count == WITNESS_NCHILDREN)
wcl = &(*wcl)->wcl_next;
if (*wcl == NULL) {
*wcl = witness_child_get();
if (*wcl == NULL)
return (0);
w_child_cnt++;
}
(*wcl)->wcl_children[(*wcl)->wcl_count++] = child;
return (1);
}
static int
itismychild(struct witness *parent, struct witness *child)
{
MPASS(child != NULL && parent != NULL);
if ((parent->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) !=
(child->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)))
panic(
"%s: parent (%s) and child (%s) are not the same lock type",
__func__, parent->w_class->lc_name,
child->w_class->lc_name);
return (insertchild(parent, child));
}
static void
removechild(struct witness *parent, struct witness *child)
{
struct witness_child_list_entry **wcl, *wcl1;
int i;
for (wcl = &parent->w_children; *wcl != NULL; wcl = &(*wcl)->wcl_next)
for (i = 0; i < (*wcl)->wcl_count; i++)
if ((*wcl)->wcl_children[i] == child)
goto found;
return;
found:
(*wcl)->wcl_count--;
if ((*wcl)->wcl_count > i)
(*wcl)->wcl_children[i] =
(*wcl)->wcl_children[(*wcl)->wcl_count];
MPASS((*wcl)->wcl_children[i] != NULL);
if ((*wcl)->wcl_count != 0)
return;
wcl1 = *wcl;
*wcl = wcl1->wcl_next;
w_child_cnt--;
witness_child_free(wcl1);
}
static int
isitmychild(struct witness *parent, struct witness *child)
{
struct witness_child_list_entry *wcl;
int i;
for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) {
for (i = 0; i < wcl->wcl_count; i++) {
if (wcl->wcl_children[i] == child)
return (1);
}
}
return (0);
}
static int
isitmydescendant(struct witness *parent, struct witness *child)
{
struct witness_child_list_entry *wcl;
int i, j;
if (isitmychild(parent, child))
return (1);
j = 0;
for (wcl = parent->w_children; wcl != NULL; wcl = wcl->wcl_next) {
MPASS(j < 1000);
for (i = 0; i < wcl->wcl_count; i++) {
if (isitmydescendant(wcl->wcl_children[i], child))
return (1);
}
j++;
}
return (0);
}
#ifdef BLESSING
static int
blessed(struct witness *w1, struct witness *w2)
{
int i;
struct witness_blessed *b;
for (i = 0; i < blessed_count; 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);
}
#endif
static struct witness *
witness_get(void)
{
struct witness *w;
if (witness_watch == 0) {
mtx_unlock_spin(&w_mtx);
return (NULL);
}
if (STAILQ_EMPTY(&w_free)) {
witness_watch = 0;
mtx_unlock_spin(&w_mtx);
printf("%s: witness exhausted\n", __func__);
return (NULL);
}
w = STAILQ_FIRST(&w_free);
STAILQ_REMOVE_HEAD(&w_free, w_list);
w_free_cnt--;
bzero(w, sizeof(*w));
return (w);
}
static void
witness_free(struct witness *w)
{
STAILQ_INSERT_HEAD(&w_free, w, w_list);
w_free_cnt++;
}
static struct witness_child_list_entry *
witness_child_get(void)
{
struct witness_child_list_entry *wcl;
if (witness_watch == 0) {
mtx_unlock_spin(&w_mtx);
return (NULL);
}
wcl = w_child_free;
if (wcl == NULL) {
witness_watch = 0;
mtx_unlock_spin(&w_mtx);
printf("%s: witness exhausted\n", __func__);
return (NULL);
}
w_child_free = wcl->wcl_next;
w_child_free_cnt--;
bzero(wcl, sizeof(*wcl));
return (wcl);
}
static void
witness_child_free(struct witness_child_list_entry *wcl)
{
wcl->wcl_next = w_child_free;
w_child_free = wcl;
w_child_free_cnt++;
}
static struct lock_list_entry *
witness_lock_list_get(void)
{
struct lock_list_entry *lle;
if (witness_watch == 0)
return (NULL);
mtx_lock_spin(&w_mtx);
lle = w_lock_list_free;
if (lle == NULL) {
witness_watch = 0;
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 *lock_list, struct lock_object *lock)
{
struct lock_list_entry *lle;
struct lock_instance *instance;
int i;
for (lle = lock_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)
{
struct lock_object *lock;
lock = instance->li_lock;
printf("%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)
printf(" (%s)", lock->lo_witness->w_name);
printf(" r = %d (%p) locked @ %s:%d\n",
instance->li_flags & LI_RECURSEMASK, lock, instance->li_file,
instance->li_line);
}
#ifdef DDB
static int
witness_thread_has_locks(struct thread *td)
{
return (td->td_sleeplocks != NULL);
}
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)
{
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]);
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)
{
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);
}
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;
KASSERT(!witness_cold, ("%s: witness_cold", __func__));
if (lock->lo_witness == NULL || witness_watch == 0 || 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)
panic("%s: lock (%s) %s not locked", __func__,
class->lc_name, lock->lo_name);
*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;
KASSERT(!witness_cold, ("%s: witness_cold", __func__));
if (lock->lo_witness == NULL || witness_watch == 0 || 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)
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;
instance->li_file = file;
instance->li_line = line;
}
void
witness_assert(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 == 0 || 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 {
panic("Lock (%s) %s is not sleep or spin!",
class->lc_name, lock->lo_name);
}
file = fixup_filename(file);
switch (flags) {
case LA_UNLOCKED:
if (instance != NULL)
panic("Lock (%s) %s locked @ %s:%d.",
class->lc_name, lock->lo_name, 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) {
panic("Lock (%s) %s not locked @ %s:%d.",
class->lc_name, lock->lo_name, file, line);
break;
}
if ((flags & LA_XLOCKED) != 0 &&
(instance->li_flags & LI_EXCLUSIVE) == 0)
panic("Lock (%s) %s not exclusively locked @ %s:%d.",
class->lc_name, lock->lo_name, file, line);
if ((flags & LA_SLOCKED) != 0 &&
(instance->li_flags & LI_EXCLUSIVE) != 0)
panic("Lock (%s) %s exclusively locked @ %s:%d.",
class->lc_name, lock->lo_name, file, line);
if ((flags & LA_RECURSED) != 0 &&
(instance->li_flags & LI_RECURSEMASK) == 0)
panic("Lock (%s) %s not recursed @ %s:%d.",
class->lc_name, lock->lo_name, file, line);
if ((flags & LA_NOTRECURSED) != 0 &&
(instance->li_flags & LI_RECURSEMASK) != 0)
panic("Lock (%s) %s recursed @ %s:%d.",
class->lc_name, lock->lo_name, file, line);
break;
default:
panic("Invalid lock assertion at %s:%d.", file, line);
}
#endif /* INVARIANT_SUPPORT */
}
#ifdef DDB
static void
witness_list(struct thread *td)
{
KASSERT(!witness_cold, ("%s: witness_cold", __func__));
KASSERT(kdb_active, ("%s: not in the debugger", __func__));
if (witness_watch == 0)
return;
witness_list_locks(&td->td_sleeplocks);
/*
* 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_SHOW_COMMAND(locks, db_witness_list)
{
struct thread *td;
if (have_addr)
td = db_lookup_thread(addr, TRUE);
else
td = kdb_thread;
witness_list(td);
}
DB_SHOW_COMMAND(alllocks, 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,
td->td_name, td, td->td_tid);
witness_list(td);
}
}
}
DB_SHOW_COMMAND(witness, db_witness_display)
{
witness_display(db_printf);
}
#endif
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