/*- * 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 $ */ /* * Machine independent bits of mutex implementation. */ #include __FBSDID("$FreeBSD$"); #include "opt_adaptive_mutexes.h" #include "opt_ddb.h" #include "opt_global.h" #include "opt_mutex_wake_all.h" #include "opt_sched.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Force MUTEX_WAKE_ALL for now. * single thread wakeup needs fixes to avoid race conditions with * priority inheritance. */ #ifndef MUTEX_WAKE_ALL #define MUTEX_WAKE_ALL #endif #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES) #define ADAPTIVE_MUTEXES #endif /* * Internal utility macros. */ #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED) #define mtx_owner(m) ((struct thread *)((m)->mtx_lock & ~MTX_FLAGMASK)) #ifdef DDB static void db_show_mtx(struct lock_object *lock); #endif static void lock_mtx(struct lock_object *lock, int how); static void lock_spin(struct lock_object *lock, int how); static int unlock_mtx(struct lock_object *lock); static int unlock_spin(struct lock_object *lock); /* * Lock classes for sleep and spin mutexes. */ struct lock_class lock_class_mtx_sleep = { .lc_name = "sleep mutex", .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE, #ifdef DDB .lc_ddb_show = db_show_mtx, #endif .lc_lock = lock_mtx, .lc_unlock = unlock_mtx, }; struct lock_class lock_class_mtx_spin = { .lc_name = "spin mutex", .lc_flags = LC_SPINLOCK | LC_RECURSABLE, #ifdef DDB .lc_ddb_show = db_show_mtx, #endif .lc_lock = lock_spin, .lc_unlock = unlock_spin, }; /* * System-wide mutexes */ struct mtx sched_lock; struct mtx Giant; #ifdef LOCK_PROFILING static inline void lock_profile_init(void) { int i; /* Initialize the mutex profiling locks */ for (i = 0; i < LPROF_LOCK_SIZE; i++) { mtx_init(&lprof_locks[i], "mprof lock", NULL, MTX_SPIN|MTX_QUIET|MTX_NOPROFILE); } } #else static inline void lock_profile_init(void) {;} #endif void lock_mtx(struct lock_object *lock, int how) { mtx_lock((struct mtx *)lock); } void lock_spin(struct lock_object *lock, int how) { panic("spin locks can only use msleep_spin"); } int unlock_mtx(struct lock_object *lock) { struct mtx *m; m = (struct mtx *)lock; mtx_assert(m, MA_OWNED | MA_NOTRECURSED); mtx_unlock(m); return (0); } int unlock_spin(struct lock_object *lock) { panic("spin locks can only use msleep_spin"); } /* * Function versions of the inlined __mtx_* macros. These are used by * modules and can also be called from assembly language if needed. */ void _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line) { MPASS(curthread != NULL); KASSERT(m->mtx_lock != MTX_DESTROYED, ("mtx_lock() of destroyed mutex @ %s:%d", file, line)); KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, file, line)); WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line); _get_sleep_lock(m, curthread, opts, file, line); LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, line); WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); curthread->td_locks++; } void _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line) { MPASS(curthread != NULL); KASSERT(m->mtx_lock != MTX_DESTROYED, ("mtx_unlock() of destroyed mutex @ %s:%d", file, line)); KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, file, line)); curthread->td_locks--; WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, line); mtx_assert(m, MA_OWNED); lock_profile_release_lock(&m->lock_object); _rel_sleep_lock(m, curthread, opts, file, line); } void _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line) { MPASS(curthread != NULL); KASSERT(m->mtx_lock != MTX_DESTROYED, ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line)); KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, ("mtx_lock_spin() of sleep mutex %s @ %s:%d", m->lock_object.lo_name, file, line)); WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line); _get_spin_lock(m, curthread, opts, file, line); LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file, line); WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); } void _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line) { MPASS(curthread != NULL); KASSERT(m->mtx_lock != MTX_DESTROYED, ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line)); KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin, ("mtx_unlock_spin() of sleep mutex %s @ %s:%d", m->lock_object.lo_name, file, line)); WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line); LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file, line); mtx_assert(m, MA_OWNED); lock_profile_release_lock(&m->lock_object); _rel_spin_lock(m); } /* * The important part of mtx_trylock{,_flags}() * Tries to acquire lock `m.' If this function is called on a mutex that * is already owned, it will recursively acquire the lock. */ int _mtx_trylock(struct mtx *m, int opts, const char *file, int line) { int rval, contested = 0; uint64_t waittime = 0; MPASS(curthread != NULL); KASSERT(m->mtx_lock != MTX_DESTROYED, ("mtx_trylock() of destroyed mutex @ %s:%d", file, line)); KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep, ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name, file, line)); if (mtx_owned(m) && (m->lock_object.lo_flags & LO_RECURSABLE) != 0) { m->mtx_recurse++; atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); rval = 1; } else rval = _obtain_lock(m, (uintptr_t)curthread); LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line); if (rval) { WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK, file, line); curthread->td_locks++; if (m->mtx_recurse == 0) lock_profile_obtain_lock_success(&m->lock_object, contested, waittime, 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, uintptr_t tid, int opts, const char *file, int line) { #ifdef ADAPTIVE_MUTEXES volatile struct thread *owner; #endif #ifdef KTR int cont_logged = 0; #endif uintptr_t v; if (mtx_owned(m)) { KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0, ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n", m->lock_object.lo_name, file, line)); m->mtx_recurse++; atomic_set_ptr(&m->mtx_lock, MTX_RECURSED); if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m); return; } if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR4(KTR_LOCK, "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d", m->lock_object.lo_name, (void *)m->mtx_lock, file, line); while (!_obtain_lock(m, tid)) { turnstile_lock(&m->lock_object); v = m->mtx_lock; /* * Check if the lock has been released while spinning for * the turnstile chain lock. */ if (v == MTX_UNOWNED) { turnstile_release(&m->lock_object); cpu_spinwait(); continue; } #ifdef MUTEX_WAKE_ALL MPASS(v != MTX_CONTESTED); #else /* * The mutex was marked contested on release. This means that * there are other threads blocked on it. Grab ownership of * it and propagate its priority to the current thread if * necessary. */ if (v == MTX_CONTESTED) { m->mtx_lock = tid | MTX_CONTESTED; turnstile_claim(&m->lock_object); break; } #endif /* * 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, v, v | MTX_CONTESTED)) { turnstile_release(&m->lock_object); cpu_spinwait(); continue; } #ifdef ADAPTIVE_MUTEXES /* * If the current owner of the lock is executing on another * CPU, spin instead of blocking. */ owner = (struct thread *)(v & ~MTX_FLAGMASK); #ifdef ADAPTIVE_GIANT if (TD_IS_RUNNING(owner)) #else if (m != &Giant && TD_IS_RUNNING(owner)) #endif { turnstile_release(&m->lock_object); while (mtx_owner(m) == owner && TD_IS_RUNNING(owner)) { cpu_spinwait(); } continue; } #endif /* ADAPTIVE_MUTEXES */ /* * We definitely must sleep for this lock. */ mtx_assert(m, MA_NOTOWNED); #ifdef KTR if (!cont_logged) { CTR6(KTR_CONTENTION, "contention: %p at %s:%d wants %s, taken by %s:%d", (void *)tid, file, line, m->lock_object.lo_name, WITNESS_FILE(&m->lock_object), WITNESS_LINE(&m->lock_object)); cont_logged = 1; } #endif /* * Block on the turnstile. */ turnstile_wait(&m->lock_object, mtx_owner(m), TS_EXCLUSIVE_QUEUE); } #ifdef KTR if (cont_logged) { CTR4(KTR_CONTENTION, "contention end: %s acquired by %p at %s:%d", m->lock_object.lo_name, (void *)tid, file, line); } #endif return; } #ifdef SMP /* * _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, uintptr_t tid, int opts, const char *file, int line) { int i = 0; struct thread *td; if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m); while (!_obtain_lock(m, tid)) { /* Give interrupts a chance while we spin. */ spinlock_exit(); while (m->mtx_lock != MTX_UNOWNED) { if (i++ < 10000000) { cpu_spinwait(); continue; } if (i < 60000000 || kdb_active || panicstr != NULL) DELAY(1); else { td = mtx_owner(m); /* If the mutex is unlocked, try again. */ if (td == NULL) continue; printf( "spin lock %p (%s) held by %p (tid %d) too long\n", m, m->lock_object.lo_name, td, td->td_tid); #ifdef WITNESS witness_display_spinlock(&m->lock_object, td); #endif panic("spin lock held too long"); } cpu_spinwait(); } spinlock_enter(); } if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m); return; } #endif /* SMP */ /* * _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 turnstile *ts; #ifndef PREEMPTION struct thread *td, *td1; #endif if (mtx_recursed(m)) { if (--(m->mtx_recurse) == 0) atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED); if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m); return; } turnstile_lock(&m->lock_object); ts = turnstile_lookup(&m->lock_object); if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m); #ifdef ADAPTIVE_MUTEXES if (ts == NULL) { _release_lock_quick(m); if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p no sleepers", m); turnstile_release(&m->lock_object); return; } #else MPASS(ts != NULL); #endif #ifndef PREEMPTION /* XXX */ td1 = turnstile_head(ts, TS_EXCLUSIVE_QUEUE); #endif #ifdef MUTEX_WAKE_ALL turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE); _release_lock_quick(m); #else if (turnstile_signal(ts, TS_EXCLUSIVE_QUEUE)) { _release_lock_quick(m); if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m); } else { m->mtx_lock = MTX_CONTESTED; if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p still contested", m); } #endif turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); #ifndef PREEMPTION /* * XXX: This is just a hack until preemption is done. However, * once preemption is done we need to either wrap the * turnstile_signal() and release of the actual lock in an * extra critical section or change the preemption code to * always just set a flag and never do instant-preempts. */ td = curthread; if (td->td_critnest > 0 || td1->td_priority >= td->td_priority) return; mtx_lock_spin(&sched_lock); if (!TD_IS_RUNNING(td1)) { #ifdef notyet if (td->td_ithd != NULL) { struct ithd *it = td->td_ithd; if (it->it_interrupted) { if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p interrupted %p", it, it->it_interrupted); intr_thd_fixup(it); } } #endif if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p switching out lock=%p", m, (void *)m->mtx_lock); mi_switch(SW_INVOL, NULL); if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", m, (void *)m->mtx_lock); } mtx_unlock_spin(&sched_lock); #endif 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) { if (panicstr != NULL || dumping) return; 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->lock_object.lo_name, file, line); if (mtx_recursed(m)) { if ((what & MA_NOTRECURSED) != 0) panic("mutex %s recursed at %s:%d", m->lock_object.lo_name, file, line); } else if ((what & MA_RECURSED) != 0) { panic("mutex %s unrecursed at %s:%d", m->lock_object.lo_name, file, line); } break; case MA_NOTOWNED: if (mtx_owned(m)) panic("mutex %s owned at %s:%d", m->lock_object.lo_name, file, line); break; default: panic("unknown mtx_assert at %s:%d", file, line); } } #endif /* * The MUTEX_DEBUG-enabled mtx_validate() * * Most of these checks have been moved off into the LO_INITIALIZED flag * maintained by the witness code. */ #ifdef MUTEX_DEBUG void mtx_validate(struct mtx *); void mtx_validate(struct mtx *m) { /* * XXX: When kernacc() does not require Giant we can reenable this check */ #ifdef notyet /* * Can't call kernacc() from early init386(), especially when * initializing Giant mutex, because some stuff in kernacc() * requires Giant itself. */ if (!cold) if (!kernacc((caddr_t)m, sizeof(m), VM_PROT_READ | VM_PROT_WRITE)) panic("Can't read and write to mutex %p", m); #endif } #endif /* * General init routine used by the MTX_SYSINIT() macro. */ void mtx_sysinit(void *arg) { struct mtx_args *margs = arg; mtx_init(margs->ma_mtx, margs->ma_desc, NULL, margs->ma_opts); } /* * Mutex initialization routine; initialize lock `m' of type contained in * `opts' with options contained in `opts' and name `name.' The optional * lock type `type' is used as a general lock category name for use with * witness. */ void mtx_init(struct mtx *m, const char *name, const char *type, int opts) { struct lock_class *class; int flags; MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0); #ifdef MUTEX_DEBUG /* Diagnostic and error correction */ mtx_validate(m); #endif /* Determine lock class and lock flags. */ if (opts & MTX_SPIN) class = &lock_class_mtx_spin; else class = &lock_class_mtx_sleep; flags = 0; if (opts & MTX_QUIET) flags |= LO_QUIET; if (opts & MTX_RECURSE) flags |= LO_RECURSABLE; if ((opts & MTX_NOWITNESS) == 0) flags |= LO_WITNESS; if (opts & MTX_DUPOK) flags |= LO_DUPOK; if (opts & MTX_NOPROFILE) flags |= LO_NOPROFILE; /* Initialize mutex. */ m->mtx_lock = MTX_UNOWNED; m->mtx_recurse = 0; lock_profile_object_init(&m->lock_object, class, name); lock_init(&m->lock_object, class, name, type, flags); } /* * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be * passed in as a flag here because if the corresponding mtx_init() was * called with MTX_QUIET set, then it will already be set in the mutex's * flags. */ void mtx_destroy(struct mtx *m) { if (!mtx_owned(m)) MPASS(mtx_unowned(m)); else { MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0); /* Perform the non-mtx related part of mtx_unlock_spin(). */ if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin) spinlock_exit(); else curthread->td_locks--; /* Tell witness this isn't locked to make it happy. */ WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__, __LINE__); } m->mtx_lock = MTX_DESTROYED; lock_profile_object_destroy(&m->lock_object); lock_destroy(&m->lock_object); } /* * Intialize the mutex code and system mutexes. This is called from the MD * startup code prior to mi_startup(). The per-CPU data space needs to be * setup before this is called. */ void mutex_init(void) { /* Setup turnstiles so that sleep mutexes work. */ init_turnstiles(); /* * Initialize mutexes. */ mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE); mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); mtx_init(&devmtx, "cdev", NULL, MTX_DEF); mtx_lock(&Giant); lock_profile_init(); } #ifdef DDB void db_show_mtx(struct lock_object *lock) { struct thread *td; struct mtx *m; m = (struct mtx *)lock; db_printf(" flags: {"); if (LOCK_CLASS(lock) == &lock_class_mtx_spin) db_printf("SPIN"); else db_printf("DEF"); if (m->lock_object.lo_flags & LO_RECURSABLE) db_printf(", RECURSE"); if (m->lock_object.lo_flags & LO_DUPOK) db_printf(", DUPOK"); db_printf("}\n"); db_printf(" state: {"); if (mtx_unowned(m)) db_printf("UNOWNED"); else { db_printf("OWNED"); if (m->mtx_lock & MTX_CONTESTED) db_printf(", CONTESTED"); if (m->mtx_lock & MTX_RECURSED) db_printf(", RECURSED"); } db_printf("}\n"); if (!mtx_unowned(m)) { td = mtx_owner(m); db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td, td->td_tid, td->td_proc->p_pid, td->td_proc->p_comm); if (mtx_recursed(m)) db_printf(" recursed: %d\n", m->mtx_recurse); } } #endif