/*- * 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 * 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 __FBSDID("$FreeBSD$"); #include "opt_ddb.h" #include "opt_witness.h" #include #include #include #include #include #include #include #include #include #include #include #include #include /* Define this to check for blessed mutexes */ #undef BLESSING #define WITNESS_COUNT 1024 #define WITNESS_CHILDCOUNT (WITNESS_COUNT * 4) /* * 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 struct witness_child_list_entry; 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; }; #ifdef BLESSING static int blessed(struct witness *, struct witness *); #endif static int 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 int rebalancetree(struct witness_list *list); static void removechild(struct witness *parent, struct witness *child); static int reparentchildren(struct witness *newparent, struct witness *oldparent); static int sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS); static void witness_displaydescendants(void(*)(const char *fmt, ...), struct witness *, int indent); static const char *fixup_filename(const char *file); static void witness_leveldescendents(struct witness *parent, int level); static void witness_levelall(void); 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_list(struct thread *td); static void witness_display_list(void(*prnt)(const char *fmt, ...), struct witness_list *list); static void witness_display(void(*)(const char *fmt, ...)); #endif SYSCTL_NODE(_debug, OID_AUTO, witness, CTLFLAG_RW, 0, "Witness Locking"); /* * If set to 0, witness is disabled. If set to 1, witness performs full lock * order checking for all locks. If set to 2 or higher, then witness skips * the full lock order check if the lock being acquired is at a higher level * (i.e. farther down in the tree) than the current lock. This last mode is * somewhat experimental and not considered fully safe. 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"); #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 heirarchy 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 heirarchy 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 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[] = { { "proctree", &lock_class_sx }, { "allproc", &lock_class_sx }, { "Giant", &lock_class_mtx_sleep }, { "filedesc structure", &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_mtx_sleep }, { "uidinfo struct", &lock_class_mtx_sleep }, { "allprison", &lock_class_mtx_sleep }, { NULL, NULL }, /* * Sockets */ { "filedesc structure", &lock_class_mtx_sleep }, { "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 }, /* * UNIX Domain Sockets */ { "unp", &lock_class_mtx_sleep }, { "so_snd", &lock_class_mtx_sleep }, { NULL, NULL }, /* * UDP/IP */ { "udp", &lock_class_mtx_sleep }, { "udpinp", &lock_class_mtx_sleep }, { "so_snd", &lock_class_mtx_sleep }, { NULL, NULL }, /* * TCP/IP */ { "tcp", &lock_class_mtx_sleep }, { "tcpinp", &lock_class_mtx_sleep }, { "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 }, /* * NFS server */ { "nfsd_mtx", &lock_class_mtx_sleep }, { "so_snd", &lock_class_mtx_sleep }, { NULL, NULL }, /* * spin locks */ #ifdef SMP { "ap boot", &lock_class_mtx_spin }, #endif { "sio", &lock_class_mtx_spin }, #ifdef __i386__ { "cy", &lock_class_mtx_spin }, #endif { "uart_hwmtx", &lock_class_mtx_spin }, { "sabtty", &lock_class_mtx_spin }, { "zstty", &lock_class_mtx_spin }, { "ng_node", &lock_class_mtx_spin }, { "ng_worklist", &lock_class_mtx_spin }, { "taskqueue_fast", &lock_class_mtx_spin }, { "intr table", &lock_class_mtx_spin }, { "ithread table lock", &lock_class_mtx_spin }, { "sleepq chain", &lock_class_mtx_spin }, { "sched lock", &lock_class_mtx_spin }, { "turnstile chain", &lock_class_mtx_spin }, { "td_contested", &lock_class_mtx_spin }, { "callout", &lock_class_mtx_spin }, { "entropy harvest mutex", &lock_class_mtx_spin }, /* * leaf locks */ { "allpmaps", &lock_class_mtx_spin }, { "vm page queue free mutex", &lock_class_mtx_spin }, { "icu", &lock_class_mtx_spin }, #ifdef SMP { "smp rendezvous", &lock_class_mtx_spin }, #if defined(__i386__) || defined(__amd64__) { "tlb", &lock_class_mtx_spin }, #endif #ifdef __sparc64__ { "ipi", &lock_class_mtx_spin }, #endif #endif { "clk", &lock_class_mtx_spin }, { "mutex profiling lock", &lock_class_mtx_spin }, { "kse 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 { 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 /* * List of all locks in the system. */ TAILQ_HEAD(, lock_object) all_locks = TAILQ_HEAD_INITIALIZER(all_locks); static struct mtx all_mtx = { { &lock_class_mtx_sleep, /* mtx_object.lo_class */ "All locks list", /* mtx_object.lo_name */ "All locks list", /* mtx_object.lo_type */ LO_INITIALIZED, /* mtx_object.lo_flags */ { NULL, NULL }, /* mtx_object.lo_list */ NULL }, /* mtx_object.lo_witness */ MTX_UNOWNED, 0 /* mtx_lock, mtx_recurse */ }; /* * This global is set to 0 once it becomes safe to use the witness code. */ static int witness_cold = 1; /* * Global variables for book keeping. */ static int lock_cur_cnt; static int lock_max_cnt; /* * The WITNESS-enabled diagnostic code. */ 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__); TAILQ_INSERT_HEAD(&all_locks, &all_mtx.mtx_object, lo_list); mtx_init(&w_mtx, "witness lock", NULL, MTX_SPIN | MTX_QUIET | MTX_NOWITNESS); 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; } } /* Iterate through all locks and add them to witness. */ mtx_lock(&all_mtx); TAILQ_FOREACH(lock, &all_locks, lo_list) { if (lock->lo_flags & LO_WITNESS) lock->lo_witness = enroll(lock->lo_type, lock->lo_class); else lock->lo_witness = NULL; } mtx_unlock(&all_mtx); /* Mark the witness code as being ready for use. */ atomic_store_rel_int(&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); error = suser(req->td); if (error != 0) return (error); if (value == witness_watch) return (0); if (value != 0) return (EINVAL); witness_watch = 0; return (0); } void witness_init(struct lock_object *lock) { struct lock_class *class; class = lock->lo_class; if (lock->lo_flags & LO_INITIALIZED) panic("%s: lock (%s) %s is already initialized", __func__, class->lc_name, lock->lo_name); 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); mtx_lock(&all_mtx); TAILQ_INSERT_TAIL(&all_locks, lock, lo_list); lock->lo_flags |= LO_INITIALIZED; lock_cur_cnt++; if (lock_cur_cnt > lock_max_cnt) lock_max_cnt = lock_cur_cnt; mtx_unlock(&all_mtx); if (!witness_cold && witness_watch != 0 && panicstr == NULL && (lock->lo_flags & LO_WITNESS) != 0) lock->lo_witness = enroll(lock->lo_type, class); else lock->lo_witness = NULL; } void witness_destroy(struct lock_object *lock) { struct witness *w; if (witness_cold) panic("lock (%s) %s destroyed while witness_cold", lock->lo_class->lc_name, lock->lo_name); if ((lock->lo_flags & LO_INITIALIZED) == 0) panic("%s: lock (%s) %s is not initialized", __func__, lock->lo_class->lc_name, lock->lo_name); /* XXX: need to verify that no one holds the lock */ w = lock->lo_witness; if (w != NULL) { mtx_lock_spin(&w_mtx); MPASS(w->w_refcount > 0); w->w_refcount--; /* * Lock is already released if we have an allocation failure * and depart() fails. */ if (w->w_refcount != 0 || depart(w)) mtx_unlock_spin(&w_mtx); } mtx_lock(&all_mtx); lock_cur_cnt--; TAILQ_REMOVE(&all_locks, lock, lo_list); lock->lo_flags &= ~LO_INITIALIZED; mtx_unlock(&all_mtx); } #ifdef DDB 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_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_type, lock1->lo_type); 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->lo_class; 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; } /* * 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. */ if (flags & LOP_TRYLOCK) 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)) return; w->w_same_squawked = 1; printf("acquiring duplicate lock of same type: \"%s\"\n", lock->lo_type); 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 have a known higher number just say ok */ if (witness_watch > 1 && w->w_level > w1->w_level) { mtx_unlock_spin(&w_mtx); return; } /* * 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 (isitmydescendant(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.mtx_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.mtx_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)) /* * Check the lock order hierarchy for a reveresal. */ if (!isitmydescendant(w, w1)) continue; /* * 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.mtx_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. */ 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, lock1->li_lock->lo_type, lock1->li_file, lock1->li_line); printf(" 2nd %p %s (%s) @ %s:%d\n", lock, lock->lo_name, lock->lo_type, file, line); } else { printf(" 1st %p %s (%s) @ %s:%d\n", lock2->li_lock, lock2->li_lock->lo_name, lock2->li_lock->lo_type, lock2->li_file, lock2->li_line); printf(" 2nd %p %s (%s) @ %s:%d\n", lock1->li_lock, lock1->li_lock->lo_name, lock1->li_lock->lo_type, lock1->li_file, lock1->li_line); printf(" 3rd %p %s (%s) @ %s:%d\n", lock, lock->lo_name, lock->lo_type, 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.mtx_object && (lock->lo_flags & LO_SLEEPABLE) != 0)) { CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__, lock->lo_type, lock1->li_lock->lo_type); 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(__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->lo_class->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->lo_class; 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 ((flags & LOP_TRYLOCK) == 0) panic("non-try upgrade of lock (%s) %s @ %s:%d", class->lc_name, lock->lo_name, file, line); if ((lock->lo_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->lo_class; 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 ((lock->lo_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->lo_class; 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.mtx_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(__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); } } /* * This isn't quite right, as witness_cold is still 0 while we * enroll all the locks initialized before witness_initialize(). */ if ((lock_class->lc_flags & LC_SPINLOCK) && !witness_cold) { mtx_unlock_spin(&w_mtx); panic("spin lock %s not in order list", description); } if ((w = witness_get()) == NULL) return (NULL); 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); else if (lock_class->lc_flags & LC_SLEEPLOCK) STAILQ_INSERT_HEAD(&w_sleep, w, w_typelist); else { mtx_unlock_spin(&w_mtx); panic("lock class %s is not sleep or spin", lock_class->lc_name); } mtx_unlock_spin(&w_mtx); return (w); } /* Don't let the door bang you on the way out... */ static int 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; else list = &w_spin; /* * 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); if (!reparentchildren(parent, w)) return (0); } /* * 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; 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); /* Finally, fixup the tree. */ return (rebalancetree(list)); } /* * Prune an entire lock order tree. We look for cases where a lock * is now both a descendant and a direct child of a given lock. In * that case, we want to remove the direct child link from the tree. * * Returns false if insertchild() fails. */ static int rebalancetree(struct witness_list *list) { struct witness *child, *parent; STAILQ_FOREACH(child, list, w_typelist) { STAILQ_FOREACH(parent, list, w_typelist) { if (!isitmychild(parent, child)) continue; removechild(parent, child); if (isitmydescendant(parent, child)) continue; if (!insertchild(parent, child)) return (0); } } witness_levelall(); return (1); } /* * 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); } (*wcl)->wcl_children[(*wcl)->wcl_count++] = child; return (1); } /* * Make all the direct descendants of oldparent be direct descendants * of newparent. */ static int reparentchildren(struct witness *newparent, struct witness *oldparent) { struct witness_child_list_entry *wcl; int i; /* Avoid making a witness a child of itself. */ MPASS(!isitmychild(oldparent, newparent)); for (wcl = oldparent->w_children; wcl != NULL; wcl = wcl->wcl_next) for (i = 0; i < wcl->wcl_count; i++) if (!insertchild(newparent, wcl->wcl_children[i])) return (0); return (1); } static int itismychild(struct witness *parent, struct witness *child) { struct witness_list *list; 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); if (!insertchild(parent, child)) return (0); if (parent->w_class->lc_flags & LC_SLEEPLOCK) list = &w_sleep; else list = &w_spin; return (rebalancetree(list)); } 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; 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); } 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); } #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); bzero(w, sizeof(*w)); return (w); } static void witness_free(struct witness *w) { STAILQ_INSERT_HEAD(&w_free, w, w_list); } 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; 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; } 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->lo_class->lc_name, lock->lo_name); if (lock->lo_type != lock->lo_name) printf(" (%s)", lock->lo_type); 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_instance *instance; KASSERT(!witness_cold, ("%s: witness_cold", __func__)); if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) return; if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0) panic("%s: lock (%s) %s is not a sleep lock", __func__, lock->lo_class->lc_name, lock->lo_name); instance = find_instance(curthread->td_sleeplocks, lock); if (instance == NULL) panic("%s: lock (%s) %s not locked", __func__, lock->lo_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_instance *instance; KASSERT(!witness_cold, ("%s: witness_cold", __func__)); if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) return; if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0) panic("%s: lock (%s) %s is not a sleep lock", __func__, lock->lo_class->lc_name, lock->lo_name); instance = find_instance(curthread->td_sleeplocks, lock); if (instance == NULL) panic("%s: lock (%s) %s not locked", __func__, lock->lo_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; if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL) return; if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) != 0) instance = find_instance(curthread->td_sleeplocks, lock); else if ((lock->lo_class->lc_flags & LC_SPINLOCK) != 0) instance = find_instance(PCPU_GET(spinlocks), lock); else { panic("Lock (%s) %s is not sleep or spin!", lock->lo_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.", lock->lo_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.", lock->lo_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.", lock->lo_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.", lock->lo_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.", lock->lo_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.", lock->lo_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 sched_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; pid_t pid; struct proc *p; if (have_addr) { pid = (addr % 16) + ((addr >> 4) % 16) * 10 + ((addr >> 8) % 16) * 100 + ((addr >> 12) % 16) * 1000 + ((addr >> 16) % 16) * 10000; /* sx_slock(&allproc_lock); */ FOREACH_PROC_IN_SYSTEM(p) { if (p->p_pid == pid) break; } /* sx_sunlock(&allproc_lock); */ if (p == NULL) { db_printf("pid %d not found\n", pid); return; } FOREACH_THREAD_IN_PROC(p, td) { witness_list(td); } } else { td = curthread; 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; printf("Process %d (%s) thread %p (%d)\n", p->p_pid, p->p_comm, td, td->td_tid); witness_list(td); } } } DB_SHOW_COMMAND(witness, db_witness_display) { witness_display(db_printf); } #endif