/*- * 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 $ * $FreeBSD$ */ /* * Machine independent bits of mutex implementation and implementation of * `witness' structure & related debugging routines. */ /* * 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 */ #include "opt_ddb.h" #include "opt_witness.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * The WITNESS-enabled mutex debug structure. */ #ifdef WITNESS struct mtx_debug { struct witness *mtxd_witness; LIST_ENTRY(mtx) mtxd_held; const char *mtxd_file; int mtxd_line; }; #define mtx_held mtx_debug->mtxd_held #define mtx_file mtx_debug->mtxd_file #define mtx_line mtx_debug->mtxd_line #define mtx_witness mtx_debug->mtxd_witness #endif /* WITNESS */ /* * Internal utility macros. */ #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED) #define mtx_owner(m) (mtx_unowned((m)) ? NULL \ : (struct proc *)((m)->mtx_lock & MTX_FLAGMASK)) #define SET_PRIO(p, pri) (p)->p_pri.pri_level = (pri) /* * Early WITNESS-enabled declarations. */ #ifdef WITNESS /* * Internal WITNESS routines which must be prototyped early. * * XXX: When/if witness code is cleaned up, it would be wise to place all * witness prototyping early in this file. */ static void witness_init(struct mtx *, int flag); static void witness_destroy(struct mtx *); static void witness_display(void(*)(const char *fmt, ...)); MALLOC_DEFINE(M_WITNESS, "witness", "witness mtx_debug structure"); /* All mutexes in system (used for debug/panic) */ static struct mtx_debug all_mtx_debug = { NULL, {NULL, NULL}, NULL, 0 }; /* * This global is set to 0 once it becomes safe to use the witness code. */ static int witness_cold = 1; #else /* WITNESS */ /* XXX XXX XXX * flag++ is sleazoid way of shuting up warning */ #define witness_init(m, flag) flag++ #define witness_destroy(m) #define witness_try_enter(m, t, f, l) #endif /* WITNESS */ /* * All mutex locks in system are kept on the all_mtx list. */ static struct mtx all_mtx = { MTX_UNOWNED, 0, 0, 0, "All mutexes queue head", TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked), { NULL, NULL }, &all_mtx, &all_mtx, #ifdef WITNESS &all_mtx_debug #else NULL #endif }; /* * Global variables for book keeping. */ static int mtx_cur_cnt; static int mtx_max_cnt; /* * Couple of strings for KTR_LOCK tracing in order to avoid duplicates. */ char STR_mtx_lock_slp[] = "GOT (sleep) %s [%p] r=%d at %s:%d"; char STR_mtx_unlock_slp[] = "REL (sleep) %s [%p] r=%d at %s:%d"; char STR_mtx_lock_spn[] = "GOT (spin) %s [%p] r=%d at %s:%d"; char STR_mtx_unlock_spn[] = "REL (spin) %s [%p] r=%d at %s:%d"; /* * Prototypes for non-exported routines. * * NOTE: Prototypes for witness routines are placed at the bottom of the file. */ static void propagate_priority(struct proc *); static void propagate_priority(struct proc *p) { int pri = p->p_pri.pri_level; struct mtx *m = p->p_blocked; mtx_assert(&sched_lock, MA_OWNED); for (;;) { struct proc *p1; p = mtx_owner(m); if (p == NULL) { /* * This really isn't quite right. Really * ought to bump priority of process that * next acquires the mutex. */ MPASS(m->mtx_lock == MTX_CONTESTED); return; } MPASS(p->p_magic == P_MAGIC); KASSERT(p->p_stat != SSLEEP, ("sleeping process owns a mutex")); if (p->p_pri.pri_level <= pri) return; /* * Bump this process' priority. */ SET_PRIO(p, pri); /* * If lock holder is actually running, just bump priority. */ if (p->p_oncpu != NOCPU) { MPASS(p->p_stat == SRUN || p->p_stat == SZOMB); return; } #ifndef SMP /* * For UP, we check to see if p is curproc (this shouldn't * ever happen however as it would mean we are in a deadlock.) */ KASSERT(p != curproc, ("Deadlock detected")); #endif /* * If on run queue move to new run queue, and * quit. */ if (p->p_stat == SRUN) { MPASS(p->p_blocked == NULL); remrunqueue(p); setrunqueue(p); return; } /* * If we aren't blocked on a mutex, we should be. */ KASSERT(p->p_stat == SMTX, ( "process %d(%s):%d holds %s but isn't blocked on a mutex\n", p->p_pid, p->p_comm, p->p_stat, m->mtx_description)); /* * Pick up the mutex that p is blocked on. */ m = p->p_blocked; MPASS(m != NULL); /* * Check if the proc needs to be moved up on * the blocked chain */ if (p == TAILQ_FIRST(&m->mtx_blocked)) { continue; } p1 = TAILQ_PREV(p, procqueue, p_procq); if (p1->p_pri.pri_level <= pri) { continue; } /* * Remove proc from blocked chain and determine where * it should be moved up to. Since we know that p1 has * a lower priority than p, we know that at least one * process in the chain has a lower priority and that * p1 will thus not be NULL after the loop. */ TAILQ_REMOVE(&m->mtx_blocked, p, p_procq); TAILQ_FOREACH(p1, &m->mtx_blocked, p_procq) { MPASS(p1->p_magic == P_MAGIC); if (p1->p_pri.pri_level > pri) break; } MPASS(p1 != NULL); TAILQ_INSERT_BEFORE(p1, p, p_procq); CTR4(KTR_LOCK, "propagate_priority: p %p moved before %p on [%p] %s", p, p1, m, m->mtx_description); } } /* * The important part of mtx_trylock{,_flags}() * Tries to acquire lock `m.' We do NOT handle recursion here; we assume that * if we're called, it's because we know we don't already own this lock. */ int _mtx_trylock(struct mtx *m, int opts, const char *file, int line) { int rval; MPASS(curproc != NULL); /* * _mtx_trylock does not accept MTX_NOSWITCH option. */ KASSERT((opts & MTX_NOSWITCH) == 0, ("mtx_trylock() called with invalid option flag(s) %d", opts)); rval = _obtain_lock(m, curproc); #ifdef WITNESS if (rval && m->mtx_witness != NULL) { /* * We do not handle recursion in _mtx_trylock; see the * note at the top of the routine. */ KASSERT(!mtx_recursed(m), ("mtx_trylock() called on a recursed mutex")); witness_try_enter(m, (opts | m->mtx_flags), file, line); } #endif /* WITNESS */ if ((opts & MTX_QUIET) == 0) CTR5(KTR_LOCK, "TRY_LOCK %s [%p] result=%d at %s:%d", m->mtx_description, m, rval, file, line); return rval; } /* * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock. * * We call this if the lock is either contested (i.e. we need to go to * sleep waiting for it), or if we need to recurse on it. */ void _mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line) { struct proc *p = curproc; if ((m->mtx_lock & MTX_FLAGMASK) == (uintptr_t)p) { m->mtx_recurse++; atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); if ((opts & MTX_QUIET) == 0) CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); return; } if ((opts & MTX_QUIET) == 0) CTR4(KTR_LOCK, "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", m->mtx_description, (void *)m->mtx_lock, file, line); while (!_obtain_lock(m, p)) { uintptr_t v; struct proc *p1; mtx_lock_spin(&sched_lock); /* * Check if the lock has been released while spinning for * the sched_lock. */ if ((v = m->mtx_lock) == MTX_UNOWNED) { mtx_unlock_spin(&sched_lock); continue; } /* * The mutex was marked contested on release. This means that * there are processes blocked on it. */ if (v == MTX_CONTESTED) { p1 = TAILQ_FIRST(&m->mtx_blocked); MPASS(p1 != NULL); m->mtx_lock = (uintptr_t)p | MTX_CONTESTED; if (p1->p_pri.pri_level < p->p_pri.pri_level) SET_PRIO(p, p1->p_pri.pri_level); mtx_unlock_spin(&sched_lock); return; } /* * If the mutex isn't already contested and a failure occurs * setting the contested bit, the mutex was either released * or the state of the MTX_RECURSED bit changed. */ if ((v & MTX_CONTESTED) == 0 && !atomic_cmpset_ptr(&m->mtx_lock, (void *)v, (void *)(v | MTX_CONTESTED))) { mtx_unlock_spin(&sched_lock); continue; } /* * We deffinately must sleep for this lock. */ mtx_assert(m, MA_NOTOWNED); #ifdef notyet /* * If we're borrowing an interrupted thread's VM context, we * must clean up before going to sleep. */ if (p->p_ithd != NULL) { struct ithd *it = p->p_ithd; if (it->it_interrupted) { if ((opts & MTX_QUIET) == 0) CTR2(KTR_LOCK, "_mtx_lock_sleep: %p interrupted %p", it, it->it_interrupted); intr_thd_fixup(it); } } #endif /* * Put us on the list of threads blocked on this mutex. */ if (TAILQ_EMPTY(&m->mtx_blocked)) { p1 = (struct proc *)(m->mtx_lock & MTX_FLAGMASK); LIST_INSERT_HEAD(&p1->p_contested, m, mtx_contested); TAILQ_INSERT_TAIL(&m->mtx_blocked, p, p_procq); } else { TAILQ_FOREACH(p1, &m->mtx_blocked, p_procq) if (p1->p_pri.pri_level > p->p_pri.pri_level) break; if (p1) TAILQ_INSERT_BEFORE(p1, p, p_procq); else TAILQ_INSERT_TAIL(&m->mtx_blocked, p, p_procq); } /* * Save who we're blocked on. */ p->p_blocked = m; p->p_mtxname = m->mtx_description; p->p_stat = SMTX; propagate_priority(p); if ((opts & MTX_QUIET) == 0) CTR3(KTR_LOCK, "_mtx_lock_sleep: p %p blocked on [%p] %s", p, m, m->mtx_description); mi_switch(); if ((opts & MTX_QUIET) == 0) CTR3(KTR_LOCK, "_mtx_lock_sleep: p %p free from blocked on [%p] %s", p, m, m->mtx_description); mtx_unlock_spin(&sched_lock); } return; } /* * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock. * * This is only called if we need to actually spin for the lock. Recursion * is handled inline. */ void _mtx_lock_spin(struct mtx *m, int opts, u_int mtx_intr, const char *file, int line) { int i = 0; if ((opts & MTX_QUIET) == 0) CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); for (;;) { if (_obtain_lock(m, curproc)) break; while (m->mtx_lock != MTX_UNOWNED) { if (i++ < 1000000) continue; if (i++ < 6000000) DELAY(1); #ifdef DDB else if (!db_active) #else else #endif panic("spin lock %s held by %p for > 5 seconds", m->mtx_description, (void *)m->mtx_lock); } } m->mtx_saveintr = mtx_intr; if ((opts & MTX_QUIET) == 0) CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); return; } /* * _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock. * * We are only called here if the lock is recursed or contested (i.e. we * need to wake up a blocked thread). */ void _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) { struct proc *p, *p1; struct mtx *m1; int pri; p = curproc; if (mtx_recursed(m)) { if (--(m->mtx_recurse) == 0) atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); if ((opts & MTX_QUIET) == 0) CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); return; } mtx_lock_spin(&sched_lock); if ((opts & MTX_QUIET) == 0) CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); p1 = TAILQ_FIRST(&m->mtx_blocked); MPASS(p->p_magic == P_MAGIC); MPASS(p1->p_magic == P_MAGIC); TAILQ_REMOVE(&m->mtx_blocked, p1, p_procq); if (TAILQ_EMPTY(&m->mtx_blocked)) { LIST_REMOVE(m, mtx_contested); _release_lock_quick(m); if ((opts & MTX_QUIET) == 0) CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m); } else atomic_store_rel_ptr(&m->mtx_lock, (void *)MTX_CONTESTED); pri = PRI_MAX; LIST_FOREACH(m1, &p->p_contested, mtx_contested) { int cp = TAILQ_FIRST(&m1->mtx_blocked)->p_pri.pri_level; if (cp < pri) pri = cp; } if (pri > p->p_pri.pri_native) pri = p->p_pri.pri_native; SET_PRIO(p, pri); if ((opts & MTX_QUIET) == 0) CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p contested setrunqueue %p", m, p1); p1->p_blocked = NULL; p1->p_stat = SRUN; setrunqueue(p1); if ((opts & MTX_NOSWITCH) == 0 && p1->p_pri.pri_level < pri) { #ifdef notyet if (p->p_ithd != NULL) { struct ithd *it = p->p_ithd; if (it->it_interrupted) { if ((opts & MTX_QUIET) == 0) CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p interrupted %p", it, it->it_interrupted); intr_thd_fixup(it); } } #endif setrunqueue(p); if ((opts & MTX_QUIET) == 0) CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p switching out lock=%p", m, (void *)m->mtx_lock); mi_switch(); if ((opts & MTX_QUIET) == 0) CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", m, (void *)m->mtx_lock); } mtx_unlock_spin(&sched_lock); return; } /* * All the unlocking of MTX_SPIN locks is done inline. * See the _rel_spin_lock() macro for the details. */ /* * The backing function for the INVARIANTS-enabled mtx_assert() */ #ifdef INVARIANT_SUPPORT void _mtx_assert(struct mtx *m, int what, const char *file, int line) { switch (what) { case MA_OWNED: case MA_OWNED | MA_RECURSED: case MA_OWNED | MA_NOTRECURSED: if (!mtx_owned(m)) panic("mutex %s not owned at %s:%d", m->mtx_description, file, line); if (mtx_recursed(m)) { if ((what & MA_NOTRECURSED) != 0) panic("mutex %s recursed at %s:%d", m->mtx_description, file, line); } else if ((what & MA_RECURSED) != 0) { panic("mutex %s unrecursed at %s:%d", m->mtx_description, file, line); } break; case MA_NOTOWNED: if (mtx_owned(m)) panic("mutex %s owned at %s:%d", m->mtx_description, file, line); break; default: panic("unknown mtx_assert at %s:%d", file, line); } } #endif /* * The MUTEX_DEBUG-enabled mtx_validate() */ #define MV_DESTROY 0 /* validate before destory */ #define MV_INIT 1 /* validate before init */ #ifdef MUTEX_DEBUG int mtx_validate __P((struct mtx *, int)); int mtx_validate(struct mtx *m, int when) { struct mtx *mp; int i; int retval = 0; #ifdef WITNESS if (witness_cold) return 0; #endif if (m == &all_mtx || cold) return 0; mtx_lock(&all_mtx); /* * XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly * we can re-enable the kernacc() checks. */ #ifndef __alpha__ MPASS(kernacc((caddr_t)all_mtx.mtx_next, sizeof(uintptr_t), VM_PROT_READ) == 1); #endif MPASS(all_mtx.mtx_next->mtx_prev == &all_mtx); for (i = 0, mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next) { #ifndef __alpha__ if (kernacc((caddr_t)mp->mtx_next, sizeof(uintptr_t), VM_PROT_READ) != 1) { panic("mtx_validate: mp=%p mp->mtx_next=%p", mp, mp->mtx_next); } #endif i++; if (i > mtx_cur_cnt) { panic("mtx_validate: too many in chain, known=%d\n", mtx_cur_cnt); } } MPASS(i == mtx_cur_cnt); switch (when) { case MV_DESTROY: for (mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next) if (mp == m) break; MPASS(mp == m); break; case MV_INIT: for (mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next) if (mp == m) { /* * Not good. This mutex already exists. */ printf("re-initing existing mutex %s\n", m->mtx_description); MPASS(m->mtx_lock == MTX_UNOWNED); retval = 1; } } mtx_unlock(&all_mtx); return (retval); } #endif /* * Mutex initialization routine; initialize lock `m' of type contained in * `opts' with options contained in `opts' and description `description.' * Place on "all_mtx" queue. */ void mtx_init(struct mtx *m, const char *description, int opts) { if ((opts & MTX_QUIET) == 0) CTR2(KTR_LOCK, "mtx_init %p (%s)", m, description); #ifdef MUTEX_DEBUG /* Diagnostic and error correction */ if (mtx_validate(m, MV_INIT)) return; #endif bzero((void *)m, sizeof *m); TAILQ_INIT(&m->mtx_blocked); #ifdef WITNESS if (!witness_cold) { m->mtx_debug = malloc(sizeof(struct mtx_debug), M_WITNESS, M_NOWAIT | M_ZERO); MPASS(m->mtx_debug != NULL); } #endif m->mtx_description = description; m->mtx_flags = opts; m->mtx_lock = MTX_UNOWNED; /* Put on all mutex queue */ mtx_lock(&all_mtx); m->mtx_next = &all_mtx; m->mtx_prev = all_mtx.mtx_prev; m->mtx_prev->mtx_next = m; all_mtx.mtx_prev = m; if (++mtx_cur_cnt > mtx_max_cnt) mtx_max_cnt = mtx_cur_cnt; mtx_unlock(&all_mtx); #ifdef WITNESS if (!witness_cold) witness_init(m, opts); #endif } /* * Remove lock `m' from all_mtx queue. */ void mtx_destroy(struct mtx *m) { #ifdef WITNESS KASSERT(!witness_cold, ("%s: Cannot destroy while still cold\n", __FUNCTION__)); #endif CTR2(KTR_LOCK, "mtx_destroy %p (%s)", m, m->mtx_description); #ifdef MUTEX_DEBUG if (m->mtx_next == NULL) panic("mtx_destroy: %p (%s) already destroyed", m, m->mtx_description); if (!mtx_owned(m)) { MPASS(m->mtx_lock == MTX_UNOWNED); } else { MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); } /* diagnostic */ mtx_validate(m, MV_DESTROY); #endif #ifdef WITNESS if (m->mtx_witness) witness_destroy(m); #endif /* WITNESS */ /* Remove from the all mutex queue */ mtx_lock(&all_mtx); m->mtx_next->mtx_prev = m->mtx_prev; m->mtx_prev->mtx_next = m->mtx_next; #ifdef MUTEX_DEBUG m->mtx_next = m->mtx_prev = NULL; #endif #ifdef WITNESS free(m->mtx_debug, M_WITNESS); m->mtx_debug = NULL; #endif mtx_cur_cnt--; mtx_unlock(&all_mtx); } /* * The WITNESS-enabled diagnostic code. */ #ifdef WITNESS static void witness_fixup(void *dummy __unused) { struct mtx *mp; /* * 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); mtx_lock(&all_mtx); /* Iterate through all mutexes and finish up mutex initialization. */ for (mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next) { mp->mtx_debug = malloc(sizeof(struct mtx_debug), M_WITNESS, M_NOWAIT | M_ZERO); MPASS(mp->mtx_debug != NULL); witness_init(mp, mp->mtx_flags); } mtx_unlock(&all_mtx); /* Mark the witness code as being ready for use. */ atomic_store_rel_int(&witness_cold, 0); mtx_lock(&Giant); } SYSINIT(wtnsfxup, SI_SUB_MUTEX, SI_ORDER_FIRST, witness_fixup, NULL) #define WITNESS_COUNT 200 #define WITNESS_NCHILDREN 2 int witness_watch = 1; struct witness { struct witness *w_next; const char *w_description; const char *w_file; int w_line; struct witness *w_morechildren; u_char w_childcnt; u_char w_Giant_squawked:1; u_char w_other_squawked:1; u_char w_same_squawked:1; u_char w_spin:1; /* MTX_SPIN type mutex. */ u_int w_level; struct witness *w_children[WITNESS_NCHILDREN]; }; struct witness_blessed { char *b_lock1; char *b_lock2; }; #ifdef DDB /* * When DDB is enabled and witness_ddb 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. */ int witness_ddb; #ifdef WITNESS_DDB TUNABLE_INT_DECL("debug.witness_ddb", 1, witness_ddb); #else TUNABLE_INT_DECL("debug.witness_ddb", 0, witness_ddb); #endif SYSCTL_INT(_debug, OID_AUTO, witness_ddb, CTLFLAG_RW, &witness_ddb, 0, ""); #endif /* DDB */ int witness_skipspin; #ifdef WITNESS_SKIPSPIN TUNABLE_INT_DECL("debug.witness_skipspin", 1, witness_skipspin); #else TUNABLE_INT_DECL("debug.witness_skipspin", 0, witness_skipspin); #endif SYSCTL_INT(_debug, OID_AUTO, witness_skipspin, CTLFLAG_RD, &witness_skipspin, 0, ""); /* * Witness-enabled globals */ static struct mtx w_mtx; static struct witness *w_free; static struct witness *w_all; static int w_inited; static int witness_dead; /* fatal error, probably no memory */ static struct witness w_data[WITNESS_COUNT]; /* * Internal witness routine prototypes */ static struct witness *enroll(const char *description, int flag); static int itismychild(struct witness *parent, struct witness *child); static void removechild(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 dup_ok(struct witness *); static int blessed(struct witness *, struct witness *); static void witness_displaydescendants(void(*)(const char *fmt, ...), struct witness *); 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 char *ignore_list[] = { "witness lock", NULL }; static char *spin_order_list[] = { #if defined(__i386__) && defined (SMP) "com", #endif "sio", #ifdef __i386__ "cy", #endif "ng_node", "ng_worklist", "ithread table lock", "ithread list lock", "sched lock", #ifdef __i386__ "clk", #endif "callout", /* * leaf locks */ #ifdef SMP #ifdef __i386__ "ap boot", "imen", #endif "smp rendezvous", #endif NULL }; static char *order_list[] = { "Giant", "proctree", "allproc", "process lock", "uidinfo hash", "uidinfo struct", NULL, NULL }; static char *dup_list[] = { "process lock", NULL }; static char *sleep_list[] = { "Giant", NULL }; /* * 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); static void witness_init(struct mtx *m, int flag) { m->mtx_witness = enroll(m->mtx_description, flag); } static void witness_destroy(struct mtx *m) { struct mtx *m1; struct proc *p; p = curproc; LIST_FOREACH(m1, &p->p_heldmtx, mtx_held) { if (m1 == m) { LIST_REMOVE(m, mtx_held); break; } } return; } static void witness_display(void(*prnt)(const char *fmt, ...)) { struct witness *w, *w1; int level, found; KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__)); witness_levelall(); /* * First, handle sleep mutexes which have been acquired at least * once. */ prnt("Sleep mutexes:\n"); for (w = w_all; w; w = w->w_next) { if (w->w_file == NULL || w->w_spin) continue; for (w1 = w_all; w1; w1 = w1->w_next) { if (isitmychild(w1, w)) break; } if (w1 != NULL) continue; /* * This lock has no anscestors, display its descendants. */ witness_displaydescendants(prnt, w); } /* * Now do spin mutexes which have been acquired at least once. */ prnt("\nSpin mutexes:\n"); level = 0; while (level < sizeof(spin_order_list) / sizeof(char *)) { found = 0; for (w = w_all; w; w = w->w_next) { if (w->w_file == NULL || !w->w_spin) continue; if (w->w_level == 1 << level) { witness_displaydescendants(prnt, w); level++; found = 1; } } if (found == 0) level++; } /* * Finally, any mutexes which have not been acquired yet. */ prnt("\nMutexes which were never acquired:\n"); for (w = w_all; w; w = w->w_next) { if (w->w_file != NULL) continue; prnt("%s\n", w->w_description); } } void witness_enter(struct mtx *m, int flags, const char *file, int line) { struct witness *w, *w1; struct mtx *m1; struct proc *p; int i; #ifdef DDB int go_into_ddb = 0; #endif /* DDB */ if (witness_cold || m->mtx_witness == NULL || panicstr) return; w = m->mtx_witness; p = curproc; if (flags & MTX_SPIN) { if ((m->mtx_flags & MTX_SPIN) == 0) panic("mutex_enter: MTX_SPIN on MTX_DEF mutex %s @" " %s:%d", m->mtx_description, file, line); if (mtx_recursed(m)) { if ((m->mtx_flags & MTX_RECURSE) == 0) panic("mutex_enter: recursion on non-recursive" " mutex %s @ %s:%d", m->mtx_description, file, line); return; } mtx_lock_spin_flags(&w_mtx, MTX_QUIET); i = PCPU_GET(witness_spin_check); if (i != 0 && w->w_level < i) { mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); panic("mutex_enter(%s:%x, MTX_SPIN) out of order @" " %s:%d already holding %s:%x", m->mtx_description, w->w_level, file, line, spin_order_list[ffs(i)-1], i); } PCPU_SET(witness_spin_check, i | w->w_level); mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); w->w_file = file; w->w_line = line; m->mtx_line = line; m->mtx_file = file; return; } if ((m->mtx_flags & MTX_SPIN) != 0) panic("mutex_enter: MTX_DEF on MTX_SPIN mutex %s @ %s:%d", m->mtx_description, file, line); if (mtx_recursed(m)) { if ((m->mtx_flags & MTX_RECURSE) == 0) panic("mutex_enter: recursion on non-recursive" " mutex %s @ %s:%d", m->mtx_description, file, line); return; } if (witness_dead) goto out; if (cold) goto out; if (!mtx_legal2block()) panic("blockable mtx_lock() of %s when not legal @ %s:%d", m->mtx_description, file, line); /* * Is this the first mutex acquired */ if ((m1 = LIST_FIRST(&p->p_heldmtx)) == NULL) goto out; if ((w1 = m1->mtx_witness) == w) { if (w->w_same_squawked || dup_ok(w)) goto out; w->w_same_squawked = 1; printf("acquring duplicate lock of same type: \"%s\"\n", m->mtx_description); printf(" 1st @ %s:%d\n", w->w_file, w->w_line); printf(" 2nd @ %s:%d\n", file, line); #ifdef DDB go_into_ddb = 1; #endif /* DDB */ goto out; } MPASS(!mtx_owned(&w_mtx)); mtx_lock_spin_flags(&w_mtx, MTX_QUIET); /* * If we have a known higher number just say ok */ if (witness_watch > 1 && w->w_level > w1->w_level) { mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); goto out; } if (isitmydescendant(m1->mtx_witness, w)) { mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); goto out; } for (i = 0; m1 != NULL; m1 = LIST_NEXT(m1, mtx_held), i++) { MPASS(i < 200); w1 = m1->mtx_witness; if (isitmydescendant(w, w1)) { mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); if (blessed(w, w1)) goto out; if (m1 == &Giant) { if (w1->w_Giant_squawked) goto out; else w1->w_Giant_squawked = 1; } else { if (w1->w_other_squawked) goto out; else w1->w_other_squawked = 1; } printf("lock order reversal\n"); printf(" 1st %s last acquired @ %s:%d\n", w->w_description, w->w_file, w->w_line); printf(" 2nd %p %s @ %s:%d\n", m1, w1->w_description, w1->w_file, w1->w_line); printf(" 3rd %p %s @ %s:%d\n", m, w->w_description, file, line); #ifdef DDB go_into_ddb = 1; #endif /* DDB */ goto out; } } m1 = LIST_FIRST(&p->p_heldmtx); if (!itismychild(m1->mtx_witness, w)) mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); out: #ifdef DDB if (witness_ddb && go_into_ddb) Debugger("witness_enter"); #endif /* DDB */ w->w_file = file; w->w_line = line; m->mtx_line = line; m->mtx_file = file; /* * If this pays off it likely means that a mutex being witnessed * is acquired in hardclock. Put it in the ignore list. It is * likely not the mutex this assert fails on. */ MPASS(m->mtx_held.le_prev == NULL); LIST_INSERT_HEAD(&p->p_heldmtx, (struct mtx*)m, mtx_held); } void witness_try_enter(struct mtx *m, int flags, const char *file, int line) { struct proc *p; struct witness *w = m->mtx_witness; if (witness_cold) return; if (panicstr) return; if (flags & MTX_SPIN) { if ((m->mtx_flags & MTX_SPIN) == 0) panic("mutex_try_enter: " "MTX_SPIN on MTX_DEF mutex %s @ %s:%d", m->mtx_description, file, line); if (mtx_recursed(m)) { if ((m->mtx_flags & MTX_RECURSE) == 0) panic("mutex_try_enter: recursion on" " non-recursive mutex %s @ %s:%d", m->mtx_description, file, line); return; } mtx_lock_spin_flags(&w_mtx, MTX_QUIET); PCPU_SET(witness_spin_check, PCPU_GET(witness_spin_check) | w->w_level); mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); w->w_file = file; w->w_line = line; m->mtx_line = line; m->mtx_file = file; return; } if ((m->mtx_flags & MTX_SPIN) != 0) panic("mutex_try_enter: MTX_DEF on MTX_SPIN mutex %s @ %s:%d", m->mtx_description, file, line); if (mtx_recursed(m)) { if ((m->mtx_flags & MTX_RECURSE) == 0) panic("mutex_try_enter: recursion on non-recursive" " mutex %s @ %s:%d", m->mtx_description, file, line); return; } w->w_file = file; w->w_line = line; m->mtx_line = line; m->mtx_file = file; p = curproc; MPASS(m->mtx_held.le_prev == NULL); LIST_INSERT_HEAD(&p->p_heldmtx, (struct mtx*)m, mtx_held); } void witness_exit(struct mtx *m, int flags, const char *file, int line) { struct witness *w; if (witness_cold || m->mtx_witness == NULL || panicstr) return; w = m->mtx_witness; if (flags & MTX_SPIN) { if ((m->mtx_flags & MTX_SPIN) == 0) panic("mutex_exit: MTX_SPIN on MTX_DEF mutex %s @" " %s:%d", m->mtx_description, file, line); if (mtx_recursed(m)) { if ((m->mtx_flags & MTX_RECURSE) == 0) panic("mutex_exit: recursion on non-recursive" " mutex %s @ %s:%d", m->mtx_description, file, line); return; } mtx_lock_spin_flags(&w_mtx, MTX_QUIET); PCPU_SET(witness_spin_check, PCPU_GET(witness_spin_check) & ~w->w_level); mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); return; } if ((m->mtx_flags & MTX_SPIN) != 0) panic("mutex_exit: MTX_DEF on MTX_SPIN mutex %s @ %s:%d", m->mtx_description, file, line); if (mtx_recursed(m)) { if ((m->mtx_flags & MTX_RECURSE) == 0) panic("mutex_exit: recursion on non-recursive" " mutex %s @ %s:%d", m->mtx_description, file, line); return; } if ((flags & MTX_NOSWITCH) == 0 && !mtx_legal2block() && !cold) panic("switchable mtx_unlock() of %s when not legal @ %s:%d", m->mtx_description, file, line); LIST_REMOVE(m, mtx_held); m->mtx_held.le_prev = NULL; } int witness_sleep(int check_only, struct mtx *mtx, const char *file, int line) { struct mtx *m; struct proc *p; char **sleep; int n = 0; KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__)); p = curproc; LIST_FOREACH(m, &p->p_heldmtx, mtx_held) { if (m == mtx) continue; for (sleep = sleep_list; *sleep!= NULL; sleep++) if (strcmp(m->mtx_description, *sleep) == 0) goto next; if (n == 0) printf("Whee!\n"); printf("%s:%d: %s with \"%s\" locked from %s:%d\n", file, line, check_only ? "could sleep" : "sleeping", m->mtx_description, m->mtx_witness->w_file, m->mtx_witness->w_line); n++; next: } #ifdef DDB if (witness_ddb && n) Debugger("witness_sleep"); #endif /* DDB */ return (n); } static struct witness * enroll(const char *description, int flag) { int i; struct witness *w, *w1; char **ignore; char **order; if (!witness_watch) return (NULL); for (ignore = ignore_list; *ignore != NULL; ignore++) if (strcmp(description, *ignore) == 0) return (NULL); if (w_inited == 0) { mtx_init(&w_mtx, "witness lock", MTX_SPIN); for (i = 0; i < WITNESS_COUNT; i++) { w = &w_data[i]; witness_free(w); } w_inited = 1; for (order = order_list; *order != NULL; order++) { w = enroll(*order, MTX_DEF); w->w_file = "order list"; for (order++; *order != NULL; order++) { w1 = enroll(*order, MTX_DEF); w1->w_file = "order list"; itismychild(w, w1); w = w1; } } } if ((flag & MTX_SPIN) && witness_skipspin) return (NULL); mtx_lock_spin_flags(&w_mtx, MTX_QUIET); for (w = w_all; w; w = w->w_next) { if (strcmp(description, w->w_description) == 0) { mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); return (w); } } if ((w = witness_get()) == NULL) return (NULL); w->w_next = w_all; w_all = w; w->w_description = description; mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); if (flag & MTX_SPIN) { w->w_spin = 1; i = 1; for (order = spin_order_list; *order != NULL; order++) { if (strcmp(description, *order) == 0) break; i <<= 1; } if (*order == NULL) panic("spin lock %s not in order list", description); w->w_level = i; } return (w); } static int itismychild(struct witness *parent, struct witness *child) { static int recursed; /* * Insert "child" after "parent" */ while (parent->w_morechildren) parent = parent->w_morechildren; if (parent->w_childcnt == WITNESS_NCHILDREN) { if ((parent->w_morechildren = witness_get()) == NULL) return (1); parent = parent->w_morechildren; } MPASS(child != NULL); parent->w_children[parent->w_childcnt++] = child; /* * now prune whole tree */ if (recursed) return (0); recursed = 1; for (child = w_all; child != NULL; child = child->w_next) { for (parent = w_all; parent != NULL; parent = parent->w_next) { if (!isitmychild(parent, child)) continue; removechild(parent, child); if (isitmydescendant(parent, child)) continue; itismychild(parent, child); } } recursed = 0; witness_levelall(); return (0); } static void removechild(struct witness *parent, struct witness *child) { struct witness *w, *w1; int i; for (w = parent; w != NULL; w = w->w_morechildren) for (i = 0; i < w->w_childcnt; i++) if (w->w_children[i] == child) goto found; return; found: for (w1 = w; w1->w_morechildren != NULL; w1 = w1->w_morechildren) continue; w->w_children[i] = w1->w_children[--w1->w_childcnt]; MPASS(w->w_children[i] != NULL); if (w1->w_childcnt != 0) return; if (w1 == parent) return; for (w = parent; w->w_morechildren != w1; w = w->w_morechildren) continue; w->w_morechildren = 0; witness_free(w1); } static int isitmychild(struct witness *parent, struct witness *child) { struct witness *w; int i; for (w = parent; w != NULL; w = w->w_morechildren) { for (i = 0; i < w->w_childcnt; i++) { if (w->w_children[i] == child) return (1); } } return (0); } static int isitmydescendant(struct witness *parent, struct witness *child) { struct witness *w; int i; int j; for (j = 0, w = parent; w != NULL; w = w->w_morechildren, j++) { MPASS(j < 1000); for (i = 0; i < w->w_childcnt; i++) { if (w->w_children[i] == child) return (1); } for (i = 0; i < w->w_childcnt; i++) { if (isitmydescendant(w->w_children[i], child)) return (1); } } return (0); } void witness_levelall (void) { struct witness *w, *w1; for (w = w_all; w; w = w->w_next) if (!(w->w_spin)) w->w_level = 0; for (w = w_all; w; w = w->w_next) { if (w->w_spin) continue; for (w1 = w_all; w1; w1 = w1->w_next) { if (isitmychild(w1, w)) break; } if (w1 != NULL) continue; witness_leveldescendents(w, 0); } } static void witness_leveldescendents(struct witness *parent, int level) { int i; struct witness *w; if (parent->w_level < level) parent->w_level = level; level++; for (w = parent; w != NULL; w = w->w_morechildren) for (i = 0; i < w->w_childcnt; i++) witness_leveldescendents(w->w_children[i], level); } static void witness_displaydescendants(void(*prnt)(const char *fmt, ...), struct witness *parent) { struct witness *w; int i; int level; level = parent->w_spin ? ffs(parent->w_level) : parent->w_level; prnt("%d", level); if (level < 10) prnt(" "); for (i = 0; i < level; i++) prnt(" "); prnt("%s", parent->w_description); if (parent->w_file != NULL) prnt(" -- last acquired @ %s:%d\n", parent->w_file, parent->w_line); for (w = parent; w != NULL; w = w->w_morechildren) for (i = 0; i < w->w_childcnt; i++) witness_displaydescendants(prnt, w->w_children[i]); } static int dup_ok(struct witness *w) { char **dup; for (dup = dup_list; *dup!= NULL; dup++) if (strcmp(w->w_description, *dup) == 0) return (1); return (0); } 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_description, b->b_lock1) == 0) { if (strcmp(w2->w_description, b->b_lock2) == 0) return (1); continue; } if (strcmp(w1->w_description, b->b_lock2) == 0) if (strcmp(w2->w_description, b->b_lock1) == 0) return (1); } return (0); } static struct witness * witness_get() { struct witness *w; if ((w = w_free) == NULL) { witness_dead = 1; mtx_unlock_spin_flags(&w_mtx, MTX_QUIET); printf("witness exhausted\n"); return (NULL); } w_free = w->w_next; bzero(w, sizeof(*w)); return (w); } static void witness_free(struct witness *w) { w->w_next = w_free; w_free = w; } int witness_list(struct proc *p) { struct mtx *m; int nheld; KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__)); nheld = 0; LIST_FOREACH(m, &p->p_heldmtx, mtx_held) { printf("\t\"%s\" (%p) locked at %s:%d\n", m->mtx_description, m, m->mtx_witness->w_file, m->mtx_witness->w_line); nheld++; } return (nheld); } #ifdef DDB DB_SHOW_COMMAND(mutexes, db_witness_list) { witness_list(curproc); } DB_SHOW_COMMAND(witness, db_witness_display) { witness_display(db_printf); } #endif void witness_save(struct mtx *m, const char **filep, int *linep) { KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__)); if (m->mtx_witness == NULL) return; *filep = m->mtx_witness->w_file; *linep = m->mtx_witness->w_line; } void witness_restore(struct mtx *m, const char *file, int line) { KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__)); if (m->mtx_witness == NULL) return; m->mtx_witness->w_file = file; m->mtx_witness->w_line = line; } #endif /* WITNESS */