/*- * SPDX-License-Identifier: BSD-2-Clause * * Copyright (c) 2008 Attilio Rao * 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(s), this list of conditions and the following disclaimer as * the first lines of this file unmodified other than the possible * addition of one or more copyright notices. * 2. Redistributions in binary form must reproduce the above copyright * notice(s), this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``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 THE COPYRIGHT HOLDER(S) 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. */ #include "opt_ddb.h" #include "opt_hwpmc_hooks.h" #include #include #include #include #include #include #include #include #include #include #include #ifdef DEBUG_LOCKS #include #endif #include #include #include #ifdef DDB #include #endif #ifdef HWPMC_HOOKS #include PMC_SOFT_DECLARE( , , lock, failed); #endif /* * Hack. There should be prio_t or similar so that this is not necessary. */ _Static_assert((PRILASTFLAG * 2) - 1 <= USHRT_MAX, "prio flags wont fit in u_short pri in struct lock"); CTASSERT(LK_UNLOCKED == (LK_UNLOCKED & ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS))); #define SQ_EXCLUSIVE_QUEUE 0 #define SQ_SHARED_QUEUE 1 #ifndef INVARIANTS #define _lockmgr_assert(lk, what, file, line) #endif #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) #ifndef DEBUG_LOCKS #define STACK_PRINT(lk) #define STACK_SAVE(lk) #define STACK_ZERO(lk) #else #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) #endif #define LOCK_LOG2(lk, string, arg1, arg2) \ if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ CTR2(KTR_LOCK, (string), (arg1), (arg2)) #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) #define GIANT_DECLARE \ int _i = 0; \ WITNESS_SAVE_DECL(Giant) #define GIANT_RESTORE() do { \ if (__predict_false(_i > 0)) { \ while (_i--) \ mtx_lock(&Giant); \ WITNESS_RESTORE(&Giant.lock_object, Giant); \ } \ } while (0) #define GIANT_SAVE() do { \ if (__predict_false(mtx_owned(&Giant))) { \ WITNESS_SAVE(&Giant.lock_object, Giant); \ while (mtx_owned(&Giant)) { \ _i++; \ mtx_unlock(&Giant); \ } \ } \ } while (0) static __always_inline bool LK_CAN_SHARE(uintptr_t x, int flags, bool fp) { if ((x & (LK_SHARE | LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == LK_SHARE) return (true); if (fp || (!(x & LK_SHARE))) return (false); if ((curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) || (curthread->td_pflags & TDP_DEADLKTREAT)) return (true); return (false); } #define LK_TRYOP(x) \ ((x) & LK_NOWAIT) #define LK_CAN_WITNESS(x) \ (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) #define LK_TRYWIT(x) \ (LK_TRYOP(x) ? LOP_TRYLOCK : 0) #define lockmgr_xlocked_v(v) \ (((v) & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) #define lockmgr_xlocked(lk) lockmgr_xlocked_v(lockmgr_read_value(lk)) static void assert_lockmgr(const struct lock_object *lock, int how); #ifdef DDB static void db_show_lockmgr(const struct lock_object *lock); #endif static void lock_lockmgr(struct lock_object *lock, uintptr_t how); #ifdef KDTRACE_HOOKS static int owner_lockmgr(const struct lock_object *lock, struct thread **owner); #endif static uintptr_t unlock_lockmgr(struct lock_object *lock); struct lock_class lock_class_lockmgr = { .lc_name = "lockmgr", .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, .lc_assert = assert_lockmgr, #ifdef DDB .lc_ddb_show = db_show_lockmgr, #endif .lc_lock = lock_lockmgr, .lc_unlock = unlock_lockmgr, #ifdef KDTRACE_HOOKS .lc_owner = owner_lockmgr, #endif }; static __read_mostly bool lk_adaptive = true; static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, "lockmgr debugging"); SYSCTL_BOOL(_debug_lockmgr, OID_AUTO, adaptive_spinning, CTLFLAG_RW, &lk_adaptive, 0, ""); #define lockmgr_delay locks_delay struct lockmgr_wait { const char *iwmesg; int ipri; int itimo; }; static __always_inline bool lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp); static __always_inline bool lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp); static void lockmgr_exit(u_int flags, struct lock_object *ilk) { struct lock_class *class; if (flags & LK_INTERLOCK) { class = LOCK_CLASS(ilk); class->lc_unlock(ilk); } } static void lockmgr_note_shared_acquire(struct lock *lk, int contested, uint64_t waittime, const char *file, int line, int flags) { LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested, waittime, file, line, LOCKSTAT_READER); LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line); WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line); TD_LOCKS_INC(curthread); TD_SLOCKS_INC(curthread); STACK_SAVE(lk); } static void lockmgr_note_shared_release(struct lock *lk, const char *file, int line) { WITNESS_UNLOCK(&lk->lock_object, 0, file, line); LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); TD_LOCKS_DEC(curthread); TD_SLOCKS_DEC(curthread); } static void lockmgr_note_exclusive_acquire(struct lock *lk, int contested, uint64_t waittime, const char *file, int line, int flags) { LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(lockmgr__acquire, lk, contested, waittime, file, line, LOCKSTAT_WRITER); LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, line); TD_LOCKS_INC(curthread); STACK_SAVE(lk); } static void lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line) { if (!lockmgr_disowned(lk)) { WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); TD_LOCKS_DEC(curthread); } LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); } static __inline struct thread * lockmgr_xholder(const struct lock *lk) { uintptr_t x; x = lockmgr_read_value(lk); return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); } /* * It assumes sleepq_lock held and returns with this one unheld. * It also assumes the generic interlock is sane and previously checked. * If LK_INTERLOCK is specified the interlock is not reacquired after the * sleep. */ static __inline int sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, const char *wmesg, int pri, int timo, int queue) { GIANT_DECLARE; struct lock_class *class; int catch, error; class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; catch = pri & PCATCH; pri &= PRIMASK; error = 0; LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); if (flags & LK_INTERLOCK) class->lc_unlock(ilk); if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) { if (lk->lk_exslpfail < USHRT_MAX) lk->lk_exslpfail++; } GIANT_SAVE(); sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? SLEEPQ_INTERRUPTIBLE : 0), queue); if ((flags & LK_TIMELOCK) && timo) sleepq_set_timeout(&lk->lock_object, timo); /* * Decisional switch for real sleeping. */ if ((flags & LK_TIMELOCK) && timo && catch) error = sleepq_timedwait_sig(&lk->lock_object, pri); else if ((flags & LK_TIMELOCK) && timo) error = sleepq_timedwait(&lk->lock_object, pri); else if (catch) error = sleepq_wait_sig(&lk->lock_object, pri); else sleepq_wait(&lk->lock_object, pri); GIANT_RESTORE(); if ((flags & LK_SLEEPFAIL) && error == 0) error = ENOLCK; return (error); } static __inline void wakeupshlk(struct lock *lk, const char *file, int line) { uintptr_t v, x, orig_x; u_int realexslp; int queue; for (;;) { x = lockmgr_read_value(lk); if (lockmgr_sunlock_try(lk, &x)) break; /* * We should have a sharer with waiters, so enter the hard * path in order to handle wakeups correctly. */ sleepq_lock(&lk->lock_object); orig_x = lockmgr_read_value(lk); retry_sleepq: x = orig_x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); v = LK_UNLOCKED; /* * If the lock has exclusive waiters, give them preference in * order to avoid deadlock with shared runners up. * If interruptible sleeps left the exclusive queue empty * avoid a starvation for the threads sleeping on the shared * queue by giving them precedence and cleaning up the * exclusive waiters bit anyway. * Please note that lk_exslpfail count may be lying about * the real number of waiters with the LK_SLEEPFAIL flag on * because they may be used in conjunction with interruptible * sleeps so lk_exslpfail might be considered an 'upper limit' * bound, including the edge cases. */ realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE); if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { if (lk->lk_exslpfail != USHRT_MAX && lk->lk_exslpfail < realexslp) { lk->lk_exslpfail = 0; queue = SQ_EXCLUSIVE_QUEUE; v |= (x & LK_SHARED_WAITERS); } else { lk->lk_exslpfail = 0; LOCK_LOG2(lk, "%s: %p has only LK_SLEEPFAIL sleepers", __func__, lk); LOCK_LOG2(lk, "%s: %p waking up threads on the exclusive queue", __func__, lk); sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); queue = SQ_SHARED_QUEUE; } } else { /* * Exclusive waiters sleeping with LK_SLEEPFAIL on * and using interruptible sleeps/timeout may have * left spourious lk_exslpfail counts on, so clean * it up anyway. */ lk->lk_exslpfail = 0; queue = SQ_SHARED_QUEUE; } if (lockmgr_sunlock_try(lk, &orig_x)) { sleepq_release(&lk->lock_object); break; } x |= LK_SHARERS_LOCK(1); if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) { orig_x = x; goto retry_sleepq; } LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : "exclusive"); sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue); sleepq_release(&lk->lock_object); break; } LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER); } static void assert_lockmgr(const struct lock_object *lock, int what) { panic("lockmgr locks do not support assertions"); } static void lock_lockmgr(struct lock_object *lock, uintptr_t how) { panic("lockmgr locks do not support sleep interlocking"); } static uintptr_t unlock_lockmgr(struct lock_object *lock) { panic("lockmgr locks do not support sleep interlocking"); } #ifdef KDTRACE_HOOKS static int owner_lockmgr(const struct lock_object *lock, struct thread **owner) { panic("lockmgr locks do not support owner inquiring"); } #endif void lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) { int iflags; MPASS((flags & ~LK_INIT_MASK) == 0); ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, &lk->lk_lock)); iflags = LO_SLEEPABLE | LO_UPGRADABLE; if (flags & LK_CANRECURSE) iflags |= LO_RECURSABLE; if ((flags & LK_NODUP) == 0) iflags |= LO_DUPOK; if (flags & LK_NOPROFILE) iflags |= LO_NOPROFILE; if ((flags & LK_NOWITNESS) == 0) iflags |= LO_WITNESS; if (flags & LK_QUIET) iflags |= LO_QUIET; if (flags & LK_IS_VNODE) iflags |= LO_IS_VNODE; if (flags & LK_NEW) iflags |= LO_NEW; iflags |= flags & LK_NOSHARE; lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); lk->lk_lock = LK_UNLOCKED; lk->lk_recurse = 0; lk->lk_exslpfail = 0; lk->lk_timo = timo; lk->lk_pri = pri; STACK_ZERO(lk); } /* * XXX: Gross hacks to manipulate external lock flags after * initialization. Used for certain vnode and buf locks. */ void lockallowshare(struct lock *lk) { lockmgr_assert(lk, KA_XLOCKED); lk->lock_object.lo_flags &= ~LK_NOSHARE; } void lockdisableshare(struct lock *lk) { lockmgr_assert(lk, KA_XLOCKED); lk->lock_object.lo_flags |= LK_NOSHARE; } void lockallowrecurse(struct lock *lk) { lockmgr_assert(lk, KA_XLOCKED); lk->lock_object.lo_flags |= LO_RECURSABLE; } void lockdisablerecurse(struct lock *lk) { lockmgr_assert(lk, KA_XLOCKED); lk->lock_object.lo_flags &= ~LO_RECURSABLE; } void lockdestroy(struct lock *lk) { KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); lock_destroy(&lk->lock_object); } static __always_inline bool lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp) { /* * If no other thread has an exclusive lock, or * no exclusive waiter is present, bump the count of * sharers. Since we have to preserve the state of * waiters, if we fail to acquire the shared lock * loop back and retry. */ while (LK_CAN_SHARE(*xp, flags, fp)) { if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp, *xp + LK_ONE_SHARER)) { return (true); } } return (false); } static __always_inline bool lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp) { for (;;) { if (LK_SHARERS(*xp) > 1 || !(*xp & LK_ALL_WAITERS)) { if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp, *xp - LK_ONE_SHARER)) return (true); continue; } break; } return (false); } static bool lockmgr_slock_adaptive(struct lock_delay_arg *lda, struct lock *lk, uintptr_t *xp, int flags) { struct thread *owner; uintptr_t x; x = *xp; MPASS(x != LK_UNLOCKED); owner = (struct thread *)LK_HOLDER(x); for (;;) { MPASS(owner != curthread); if (owner == (struct thread *)LK_KERNPROC) return (false); if ((x & LK_SHARE) && LK_SHARERS(x) > 0) return (false); if (owner == NULL) return (false); if (!TD_IS_RUNNING(owner)) return (false); if ((x & LK_ALL_WAITERS) != 0) return (false); lock_delay(lda); x = lockmgr_read_value(lk); if (LK_CAN_SHARE(x, flags, false)) { *xp = x; return (true); } owner = (struct thread *)LK_HOLDER(x); } } static __noinline int lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk, const char *file, int line, struct lockmgr_wait *lwa) { uintptr_t tid, x; int error = 0; const char *iwmesg; int ipri, itimo; #ifdef KDTRACE_HOOKS uint64_t sleep_time = 0; #endif #ifdef LOCK_PROFILING uint64_t waittime = 0; int contested = 0; #endif struct lock_delay_arg lda; if (SCHEDULER_STOPPED()) goto out; tid = (uintptr_t)curthread; if (LK_CAN_WITNESS(flags)) WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, file, line, flags & LK_INTERLOCK ? ilk : NULL); x = lockmgr_read_value(lk); lock_delay_arg_init(&lda, &lockmgr_delay); if (!lk_adaptive) flags &= ~LK_ADAPTIVE; /* * The lock may already be locked exclusive by curthread, * avoid deadlock. */ if (LK_HOLDER(x) == tid) { LOCK_LOG2(lk, "%s: %p already held in exclusive mode", __func__, lk); error = EDEADLK; goto out; } for (;;) { if (lockmgr_slock_try(lk, &x, flags, false)) break; lock_profile_obtain_lock_failed(&lk->lock_object, false, &contested, &waittime); if ((flags & (LK_ADAPTIVE | LK_INTERLOCK)) == LK_ADAPTIVE) { if (lockmgr_slock_adaptive(&lda, lk, &x, flags)) continue; } #ifdef HWPMC_HOOKS PMC_SOFT_CALL( , , lock, failed); #endif /* * If the lock is expected to not sleep just give up * and return. */ if (LK_TRYOP(flags)) { LOCK_LOG2(lk, "%s: %p fails the try operation", __func__, lk); error = EBUSY; break; } /* * Acquire the sleepqueue chain lock because we * probabilly will need to manipulate waiters flags. */ sleepq_lock(&lk->lock_object); x = lockmgr_read_value(lk); retry_sleepq: /* * if the lock can be acquired in shared mode, try * again. */ if (LK_CAN_SHARE(x, flags, false)) { sleepq_release(&lk->lock_object); continue; } /* * Try to set the LK_SHARED_WAITERS flag. If we fail, * loop back and retry. */ if ((x & LK_SHARED_WAITERS) == 0) { if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, x | LK_SHARED_WAITERS)) { goto retry_sleepq; } LOCK_LOG2(lk, "%s: %p set shared waiters flag", __func__, lk); } if (lwa == NULL) { iwmesg = lk->lock_object.lo_name; ipri = lk->lk_pri; itimo = lk->lk_timo; } else { iwmesg = lwa->iwmesg; ipri = lwa->ipri; itimo = lwa->itimo; } /* * As far as we have been unable to acquire the * shared lock and the shared waiters flag is set, * we will sleep. */ #ifdef KDTRACE_HOOKS sleep_time -= lockstat_nsecs(&lk->lock_object); #endif error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, SQ_SHARED_QUEUE); #ifdef KDTRACE_HOOKS sleep_time += lockstat_nsecs(&lk->lock_object); #endif flags &= ~LK_INTERLOCK; if (error) { LOCK_LOG3(lk, "%s: interrupted sleep for %p with %d", __func__, lk, error); break; } LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", __func__, lk); x = lockmgr_read_value(lk); } if (error == 0) { #ifdef KDTRACE_HOOKS if (sleep_time != 0) LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time, LOCKSTAT_READER, (x & LK_SHARE) == 0, (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x)); #endif #ifdef LOCK_PROFILING lockmgr_note_shared_acquire(lk, contested, waittime, file, line, flags); #else lockmgr_note_shared_acquire(lk, 0, 0, file, line, flags); #endif } out: lockmgr_exit(flags, ilk); return (error); } static bool lockmgr_xlock_adaptive(struct lock_delay_arg *lda, struct lock *lk, uintptr_t *xp) { struct thread *owner; uintptr_t x; x = *xp; MPASS(x != LK_UNLOCKED); owner = (struct thread *)LK_HOLDER(x); for (;;) { MPASS(owner != curthread); if (owner == NULL) return (false); if ((x & LK_SHARE) && LK_SHARERS(x) > 0) return (false); if (owner == (struct thread *)LK_KERNPROC) return (false); if (!TD_IS_RUNNING(owner)) return (false); if ((x & LK_ALL_WAITERS) != 0) return (false); lock_delay(lda); x = lockmgr_read_value(lk); if (x == LK_UNLOCKED) { *xp = x; return (true); } owner = (struct thread *)LK_HOLDER(x); } } static __noinline int lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk, const char *file, int line, struct lockmgr_wait *lwa) { struct lock_class *class; uintptr_t tid, x, v; int error = 0; const char *iwmesg; int ipri, itimo; #ifdef KDTRACE_HOOKS uint64_t sleep_time = 0; #endif #ifdef LOCK_PROFILING uint64_t waittime = 0; int contested = 0; #endif struct lock_delay_arg lda; if (SCHEDULER_STOPPED()) goto out; tid = (uintptr_t)curthread; if (LK_CAN_WITNESS(flags)) WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? ilk : NULL); /* * If curthread already holds the lock and this one is * allowed to recurse, simply recurse on it. */ if (lockmgr_xlocked(lk)) { if ((flags & LK_CANRECURSE) == 0 && (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { /* * If the lock is expected to not panic just * give up and return. */ if (LK_TRYOP(flags)) { LOCK_LOG2(lk, "%s: %p fails the try operation", __func__, lk); error = EBUSY; goto out; } if (flags & LK_INTERLOCK) { class = LOCK_CLASS(ilk); class->lc_unlock(ilk); } STACK_PRINT(lk); panic("%s: recursing on non recursive lockmgr %p " "@ %s:%d\n", __func__, lk, file, line); } atomic_set_ptr(&lk->lk_lock, LK_WRITER_RECURSED); lk->lk_recurse++; LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, line); TD_LOCKS_INC(curthread); goto out; } x = LK_UNLOCKED; lock_delay_arg_init(&lda, &lockmgr_delay); if (!lk_adaptive) flags &= ~LK_ADAPTIVE; for (;;) { if (x == LK_UNLOCKED) { if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, tid)) break; continue; } lock_profile_obtain_lock_failed(&lk->lock_object, false, &contested, &waittime); if ((flags & (LK_ADAPTIVE | LK_INTERLOCK)) == LK_ADAPTIVE) { if (lockmgr_xlock_adaptive(&lda, lk, &x)) continue; } #ifdef HWPMC_HOOKS PMC_SOFT_CALL( , , lock, failed); #endif /* * If the lock is expected to not sleep just give up * and return. */ if (LK_TRYOP(flags)) { LOCK_LOG2(lk, "%s: %p fails the try operation", __func__, lk); error = EBUSY; break; } /* * Acquire the sleepqueue chain lock because we * probabilly will need to manipulate waiters flags. */ sleepq_lock(&lk->lock_object); x = lockmgr_read_value(lk); retry_sleepq: /* * if the lock has been released while we spun on * the sleepqueue chain lock just try again. */ if (x == LK_UNLOCKED) { sleepq_release(&lk->lock_object); continue; } /* * The lock can be in the state where there is a * pending queue of waiters, but still no owner. * This happens when the lock is contested and an * owner is going to claim the lock. * If curthread is the one successfully acquiring it * claim lock ownership and return, preserving waiters * flags. */ v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); if ((x & ~v) == LK_UNLOCKED) { v &= ~LK_EXCLUSIVE_SPINNERS; if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x, tid | v)) { sleepq_release(&lk->lock_object); LOCK_LOG2(lk, "%s: %p claimed by a new writer", __func__, lk); break; } goto retry_sleepq; } /* * Try to set the LK_EXCLUSIVE_WAITERS flag. If we * fail, loop back and retry. */ if ((x & LK_EXCLUSIVE_WAITERS) == 0) { if (!atomic_fcmpset_ptr(&lk->lk_lock, &x, x | LK_EXCLUSIVE_WAITERS)) { goto retry_sleepq; } LOCK_LOG2(lk, "%s: %p set excl waiters flag", __func__, lk); } if (lwa == NULL) { iwmesg = lk->lock_object.lo_name; ipri = lk->lk_pri; itimo = lk->lk_timo; } else { iwmesg = lwa->iwmesg; ipri = lwa->ipri; itimo = lwa->itimo; } /* * As far as we have been unable to acquire the * exclusive lock and the exclusive waiters flag * is set, we will sleep. */ #ifdef KDTRACE_HOOKS sleep_time -= lockstat_nsecs(&lk->lock_object); #endif error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, SQ_EXCLUSIVE_QUEUE); #ifdef KDTRACE_HOOKS sleep_time += lockstat_nsecs(&lk->lock_object); #endif flags &= ~LK_INTERLOCK; if (error) { LOCK_LOG3(lk, "%s: interrupted sleep for %p with %d", __func__, lk, error); break; } LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", __func__, lk); x = lockmgr_read_value(lk); } if (error == 0) { #ifdef KDTRACE_HOOKS if (sleep_time != 0) LOCKSTAT_RECORD4(lockmgr__block, lk, sleep_time, LOCKSTAT_WRITER, (x & LK_SHARE) == 0, (x & LK_SHARE) == 0 ? 0 : LK_SHARERS(x)); #endif #ifdef LOCK_PROFILING lockmgr_note_exclusive_acquire(lk, contested, waittime, file, line, flags); #else lockmgr_note_exclusive_acquire(lk, 0, 0, file, line, flags); #endif } out: lockmgr_exit(flags, ilk); return (error); } static __noinline int lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk, const char *file, int line, struct lockmgr_wait *lwa) { uintptr_t tid, v, setv; int error = 0; int op; if (SCHEDULER_STOPPED()) goto out; tid = (uintptr_t)curthread; _lockmgr_assert(lk, KA_SLOCKED, file, line); op = flags & LK_TYPE_MASK; v = lockmgr_read_value(lk); for (;;) { if (LK_SHARERS(v) > 1) { if (op == LK_TRYUPGRADE) { LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", __func__, lk); error = EBUSY; goto out; } if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &v, v - LK_ONE_SHARER)) { lockmgr_note_shared_release(lk, file, line); goto out_xlock; } continue; } MPASS((v & ~LK_ALL_WAITERS) == LK_SHARERS_LOCK(1)); setv = tid; setv |= (v & LK_ALL_WAITERS); /* * Try to switch from one shared lock to an exclusive one. * We need to preserve waiters flags during the operation. */ if (atomic_fcmpset_ptr(&lk->lk_lock, &v, setv)) { LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, line); WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, line); LOCKSTAT_RECORD0(lockmgr__upgrade, lk); TD_SLOCKS_DEC(curthread); goto out; } } out_xlock: error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa); flags &= ~LK_INTERLOCK; out: lockmgr_exit(flags, ilk); return (error); } int lockmgr_lock_flags(struct lock *lk, u_int flags, struct lock_object *ilk, const char *file, int line) { struct lock_class *class; uintptr_t x, tid; u_int op; bool locked; if (SCHEDULER_STOPPED()) return (0); op = flags & LK_TYPE_MASK; locked = false; switch (op) { case LK_SHARED: if (LK_CAN_WITNESS(flags)) WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, file, line, flags & LK_INTERLOCK ? ilk : NULL); if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE)) break; x = lockmgr_read_value(lk); if (lockmgr_slock_try(lk, &x, flags, true)) { lockmgr_note_shared_acquire(lk, 0, 0, file, line, flags); locked = true; } else { return (lockmgr_slock_hard(lk, flags, ilk, file, line, NULL)); } break; case LK_EXCLUSIVE: if (LK_CAN_WITNESS(flags)) WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? ilk : NULL); tid = (uintptr_t)curthread; if (lockmgr_read_value(lk) == LK_UNLOCKED && atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { lockmgr_note_exclusive_acquire(lk, 0, 0, file, line, flags); locked = true; } else { return (lockmgr_xlock_hard(lk, flags, ilk, file, line, NULL)); } break; case LK_UPGRADE: case LK_TRYUPGRADE: return (lockmgr_upgrade(lk, flags, ilk, file, line, NULL)); default: break; } if (__predict_true(locked)) { if (__predict_false(flags & LK_INTERLOCK)) { class = LOCK_CLASS(ilk); class->lc_unlock(ilk); } return (0); } else { return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT, LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line)); } } static __noinline int lockmgr_sunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk, const char *file, int line) { if (!SCHEDULER_STOPPED()) wakeupshlk(lk, file, line); lockmgr_exit(flags, ilk); return (0); } static __noinline int lockmgr_xunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk, const char *file, int line) { uintptr_t tid, v; u_int realexslp; int queue; if (SCHEDULER_STOPPED()) goto out; tid = (uintptr_t)curthread; /* * As first option, treact the lock as if it has not * any waiter. * Fix-up the tid var if the lock has been disowned. */ if (lockmgr_disowned_v(x)) tid = LK_KERNPROC; /* * The lock is held in exclusive mode. * If the lock is recursed also, then unrecurse it. */ if (lockmgr_recursed_v(x)) { LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk); lk->lk_recurse--; if (lk->lk_recurse == 0) atomic_clear_ptr(&lk->lk_lock, LK_WRITER_RECURSED); goto out; } if (tid != LK_KERNPROC) LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_WRITER); if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) goto out; sleepq_lock(&lk->lock_object); x = lockmgr_read_value(lk); v = LK_UNLOCKED; /* * If the lock has exclusive waiters, give them * preference in order to avoid deadlock with * shared runners up. * If interruptible sleeps left the exclusive queue * empty avoid a starvation for the threads sleeping * on the shared queue by giving them precedence * and cleaning up the exclusive waiters bit anyway. * Please note that lk_exslpfail count may be lying * about the real number of waiters with the * LK_SLEEPFAIL flag on because they may be used in * conjunction with interruptible sleeps so * lk_exslpfail might be considered an 'upper limit' * bound, including the edge cases. */ MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE); if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { if (lk->lk_exslpfail != USHRT_MAX && lk->lk_exslpfail < realexslp) { lk->lk_exslpfail = 0; queue = SQ_EXCLUSIVE_QUEUE; v |= (x & LK_SHARED_WAITERS); } else { lk->lk_exslpfail = 0; LOCK_LOG2(lk, "%s: %p has only LK_SLEEPFAIL sleepers", __func__, lk); LOCK_LOG2(lk, "%s: %p waking up threads on the exclusive queue", __func__, lk); sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); queue = SQ_SHARED_QUEUE; } } else { /* * Exclusive waiters sleeping with LK_SLEEPFAIL * on and using interruptible sleeps/timeout * may have left spourious lk_exslpfail counts * on, so clean it up anyway. */ lk->lk_exslpfail = 0; queue = SQ_SHARED_QUEUE; } LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : "exclusive"); atomic_store_rel_ptr(&lk->lk_lock, v); sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue); sleepq_release(&lk->lock_object); out: lockmgr_exit(flags, ilk); return (0); } /* * Lightweight entry points for common operations. * * Functionality is similar to sx locks, in that none of the additional lockmgr * features are supported. To be clear, these are NOT supported: * 1. shared locking disablement * 2. returning with an error after sleep * 3. unlocking the interlock * * If in doubt, use lockmgr_lock_flags. */ int lockmgr_slock(struct lock *lk, u_int flags, const char *file, int line) { uintptr_t x; MPASS((flags & LK_TYPE_MASK) == LK_SHARED); MPASS((flags & LK_INTERLOCK) == 0); MPASS((lk->lock_object.lo_flags & LK_NOSHARE) == 0); if (LK_CAN_WITNESS(flags)) WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, file, line, NULL); x = lockmgr_read_value(lk); if (__predict_true(lockmgr_slock_try(lk, &x, flags, true))) { lockmgr_note_shared_acquire(lk, 0, 0, file, line, flags); return (0); } return (lockmgr_slock_hard(lk, flags | LK_ADAPTIVE, NULL, file, line, NULL)); } int lockmgr_xlock(struct lock *lk, u_int flags, const char *file, int line) { uintptr_t tid; MPASS((flags & LK_TYPE_MASK) == LK_EXCLUSIVE); MPASS((flags & LK_INTERLOCK) == 0); if (LK_CAN_WITNESS(flags)) WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); tid = (uintptr_t)curthread; if (atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { lockmgr_note_exclusive_acquire(lk, 0, 0, file, line, flags); return (0); } return (lockmgr_xlock_hard(lk, flags | LK_ADAPTIVE, NULL, file, line, NULL)); } int lockmgr_unlock(struct lock *lk) { uintptr_t x, tid; const char *file; int line; file = __FILE__; line = __LINE__; _lockmgr_assert(lk, KA_LOCKED, file, line); x = lockmgr_read_value(lk); if (__predict_true(x & LK_SHARE) != 0) { lockmgr_note_shared_release(lk, file, line); if (lockmgr_sunlock_try(lk, &x)) { LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER); } else { return (lockmgr_sunlock_hard(lk, x, LK_RELEASE, NULL, file, line)); } } else { tid = (uintptr_t)curthread; lockmgr_note_exclusive_release(lk, file, line); if (x == tid && atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) { LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk,LOCKSTAT_WRITER); } else { return (lockmgr_xunlock_hard(lk, x, LK_RELEASE, NULL, file, line)); } } return (0); } int __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, const char *wmesg, int pri, int timo, const char *file, int line) { GIANT_DECLARE; struct lockmgr_wait lwa; struct lock_class *class; const char *iwmesg; uintptr_t tid, v, x; u_int op, realexslp; int error, ipri, itimo, queue; #ifdef LOCK_PROFILING uint64_t waittime = 0; int contested = 0; #endif if (SCHEDULER_STOPPED()) return (0); error = 0; tid = (uintptr_t)curthread; op = (flags & LK_TYPE_MASK); iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; lwa.iwmesg = iwmesg; lwa.ipri = ipri; lwa.itimo = itimo; MPASS((flags & ~LK_TOTAL_MASK) == 0); KASSERT((op & (op - 1)) == 0, ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || (op != LK_DOWNGRADE && op != LK_RELEASE), ("%s: Invalid flags in regard of the operation desired @ %s:%d", __func__, file, line)); KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", __func__, file, line)); KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread, lk->lock_object.lo_name, file, line)); class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; if (lk->lock_object.lo_flags & LK_NOSHARE) { switch (op) { case LK_SHARED: op = LK_EXCLUSIVE; break; case LK_UPGRADE: case LK_TRYUPGRADE: case LK_DOWNGRADE: _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); if (flags & LK_INTERLOCK) class->lc_unlock(ilk); return (0); } } switch (op) { case LK_SHARED: return (lockmgr_slock_hard(lk, flags, ilk, file, line, &lwa)); break; case LK_UPGRADE: case LK_TRYUPGRADE: return (lockmgr_upgrade(lk, flags, ilk, file, line, &lwa)); break; case LK_EXCLUSIVE: return (lockmgr_xlock_hard(lk, flags, ilk, file, line, &lwa)); break; case LK_DOWNGRADE: _lockmgr_assert(lk, KA_XLOCKED, file, line); WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); /* * Panic if the lock is recursed. */ if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { if (flags & LK_INTERLOCK) class->lc_unlock(ilk); panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n", __func__, iwmesg, file, line); } TD_SLOCKS_INC(curthread); /* * In order to preserve waiters flags, just spin. */ for (;;) { x = lockmgr_read_value(lk); MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); x &= LK_ALL_WAITERS; if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, LK_SHARERS_LOCK(1) | x)) break; cpu_spinwait(); } LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); LOCKSTAT_RECORD0(lockmgr__downgrade, lk); break; case LK_RELEASE: _lockmgr_assert(lk, KA_LOCKED, file, line); x = lockmgr_read_value(lk); if (__predict_true(x & LK_SHARE) != 0) { lockmgr_note_shared_release(lk, file, line); return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line)); } else { lockmgr_note_exclusive_release(lk, file, line); return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line)); } break; case LK_DRAIN: if (LK_CAN_WITNESS(flags)) WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ? ilk : NULL); /* * Trying to drain a lock we already own will result in a * deadlock. */ if (lockmgr_xlocked(lk)) { if (flags & LK_INTERLOCK) class->lc_unlock(ilk); panic("%s: draining %s with the lock held @ %s:%d\n", __func__, iwmesg, file, line); } for (;;) { if (lk->lk_lock == LK_UNLOCKED && atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) break; #ifdef HWPMC_HOOKS PMC_SOFT_CALL( , , lock, failed); #endif lock_profile_obtain_lock_failed(&lk->lock_object, false, &contested, &waittime); /* * If the lock is expected to not sleep just give up * and return. */ if (LK_TRYOP(flags)) { LOCK_LOG2(lk, "%s: %p fails the try operation", __func__, lk); error = EBUSY; break; } /* * Acquire the sleepqueue chain lock because we * probabilly will need to manipulate waiters flags. */ sleepq_lock(&lk->lock_object); x = lockmgr_read_value(lk); /* * if the lock has been released while we spun on * the sleepqueue chain lock just try again. */ if (x == LK_UNLOCKED) { sleepq_release(&lk->lock_object); continue; } v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); if ((x & ~v) == LK_UNLOCKED) { v = (x & ~LK_EXCLUSIVE_SPINNERS); /* * If interruptible sleeps left the exclusive * queue empty avoid a starvation for the * threads sleeping on the shared queue by * giving them precedence and cleaning up the * exclusive waiters bit anyway. * Please note that lk_exslpfail count may be * lying about the real number of waiters with * the LK_SLEEPFAIL flag on because they may * be used in conjunction with interruptible * sleeps so lk_exslpfail might be considered * an 'upper limit' bound, including the edge * cases. */ if (v & LK_EXCLUSIVE_WAITERS) { queue = SQ_EXCLUSIVE_QUEUE; v &= ~LK_EXCLUSIVE_WAITERS; } else { /* * Exclusive waiters sleeping with * LK_SLEEPFAIL on and using * interruptible sleeps/timeout may * have left spourious lk_exslpfail * counts on, so clean it up anyway. */ MPASS(v & LK_SHARED_WAITERS); lk->lk_exslpfail = 0; queue = SQ_SHARED_QUEUE; v &= ~LK_SHARED_WAITERS; } if (queue == SQ_EXCLUSIVE_QUEUE) { realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE); if (lk->lk_exslpfail >= realexslp) { lk->lk_exslpfail = 0; queue = SQ_SHARED_QUEUE; v &= ~LK_SHARED_WAITERS; if (realexslp != 0) { LOCK_LOG2(lk, "%s: %p has only LK_SLEEPFAIL sleepers", __func__, lk); LOCK_LOG2(lk, "%s: %p waking up threads on the exclusive queue", __func__, lk); sleepq_broadcast( &lk->lock_object, SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); } } else lk->lk_exslpfail = 0; } if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { sleepq_release(&lk->lock_object); continue; } LOCK_LOG3(lk, "%s: %p waking up all threads on the %s queue", __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : "exclusive"); sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue); /* * If shared waiters have been woken up we need * to wait for one of them to acquire the lock * before to set the exclusive waiters in * order to avoid a deadlock. */ if (queue == SQ_SHARED_QUEUE) { for (v = lk->lk_lock; (v & LK_SHARE) && !LK_SHARERS(v); v = lk->lk_lock) cpu_spinwait(); } } /* * Try to set the LK_EXCLUSIVE_WAITERS flag. If we * fail, loop back and retry. */ if ((x & LK_EXCLUSIVE_WAITERS) == 0) { if (!atomic_cmpset_ptr(&lk->lk_lock, x, x | LK_EXCLUSIVE_WAITERS)) { sleepq_release(&lk->lock_object); continue; } LOCK_LOG2(lk, "%s: %p set drain waiters flag", __func__, lk); } /* * As far as we have been unable to acquire the * exclusive lock and the exclusive waiters flag * is set, we will sleep. */ if (flags & LK_INTERLOCK) { class->lc_unlock(ilk); flags &= ~LK_INTERLOCK; } GIANT_SAVE(); sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, SQ_EXCLUSIVE_QUEUE); sleepq_wait(&lk->lock_object, ipri & PRIMASK); GIANT_RESTORE(); LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", __func__, lk); } if (error == 0) { lock_profile_obtain_lock_success(&lk->lock_object, false, contested, waittime, file, line); LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, lk->lk_recurse, file, line); WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, line); TD_LOCKS_INC(curthread); STACK_SAVE(lk); } break; default: if (flags & LK_INTERLOCK) class->lc_unlock(ilk); panic("%s: unknown lockmgr request 0x%x\n", __func__, op); } if (flags & LK_INTERLOCK) class->lc_unlock(ilk); return (error); } void _lockmgr_disown(struct lock *lk, const char *file, int line) { uintptr_t tid, x; if (SCHEDULER_STOPPED()) return; tid = (uintptr_t)curthread; _lockmgr_assert(lk, KA_XLOCKED, file, line); /* * Panic if the lock is recursed. */ if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) panic("%s: disown a recursed lockmgr @ %s:%d\n", __func__, file, line); /* * If the owner is already LK_KERNPROC just skip the whole operation. */ if (LK_HOLDER(lk->lk_lock) != tid) return; lock_profile_release_lock(&lk->lock_object, false); LOCKSTAT_RECORD1(lockmgr__disown, lk, LOCKSTAT_WRITER); LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); TD_LOCKS_DEC(curthread); STACK_SAVE(lk); /* * In order to preserve waiters flags, just spin. */ for (;;) { x = lockmgr_read_value(lk); MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); x &= LK_ALL_WAITERS; if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, LK_KERNPROC | x)) return; cpu_spinwait(); } } void lockmgr_printinfo(const struct lock *lk) { struct thread *td; uintptr_t x; if (lk->lk_lock == LK_UNLOCKED) printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); else if (lk->lk_lock & LK_SHARE) printf("lock type %s: SHARED (count %ju)\n", lk->lock_object.lo_name, (uintmax_t)LK_SHARERS(lk->lk_lock)); else { td = lockmgr_xholder(lk); if (td == (struct thread *)LK_KERNPROC) printf("lock type %s: EXCL by KERNPROC\n", lk->lock_object.lo_name); else printf("lock type %s: EXCL by thread %p " "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, td, td->td_proc->p_pid, td->td_proc->p_comm, td->td_tid); } x = lk->lk_lock; if (x & LK_EXCLUSIVE_WAITERS) printf(" with exclusive waiters pending\n"); if (x & LK_SHARED_WAITERS) printf(" with shared waiters pending\n"); if (x & LK_EXCLUSIVE_SPINNERS) printf(" with exclusive spinners pending\n"); STACK_PRINT(lk); } int lockstatus(const struct lock *lk) { uintptr_t v, x; int ret; ret = LK_SHARED; x = lockmgr_read_value(lk); v = LK_HOLDER(x); if ((x & LK_SHARE) == 0) { if (v == (uintptr_t)curthread || v == LK_KERNPROC) ret = LK_EXCLUSIVE; else ret = LK_EXCLOTHER; } else if (x == LK_UNLOCKED) ret = 0; return (ret); } #ifdef INVARIANT_SUPPORT FEATURE(invariant_support, "Support for modules compiled with INVARIANTS option"); #ifndef INVARIANTS #undef _lockmgr_assert #endif void _lockmgr_assert(const struct lock *lk, int what, const char *file, int line) { int slocked = 0; if (SCHEDULER_STOPPED()) return; switch (what) { case KA_SLOCKED: case KA_SLOCKED | KA_NOTRECURSED: case KA_SLOCKED | KA_RECURSED: slocked = 1; case KA_LOCKED: case KA_LOCKED | KA_NOTRECURSED: case KA_LOCKED | KA_RECURSED: #ifdef WITNESS /* * We cannot trust WITNESS if the lock is held in exclusive * mode and a call to lockmgr_disown() happened. * Workaround this skipping the check if the lock is held in * exclusive mode even for the KA_LOCKED case. */ if (slocked || (lk->lk_lock & LK_SHARE)) { witness_assert(&lk->lock_object, what, file, line); break; } #endif if (lk->lk_lock == LK_UNLOCKED || ((lk->lk_lock & LK_SHARE) == 0 && (slocked || (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) panic("Lock %s not %slocked @ %s:%d\n", lk->lock_object.lo_name, slocked ? "share" : "", file, line); if ((lk->lk_lock & LK_SHARE) == 0) { if (lockmgr_recursed(lk)) { if (what & KA_NOTRECURSED) panic("Lock %s recursed @ %s:%d\n", lk->lock_object.lo_name, file, line); } else if (what & KA_RECURSED) panic("Lock %s not recursed @ %s:%d\n", lk->lock_object.lo_name, file, line); } break; case KA_XLOCKED: case KA_XLOCKED | KA_NOTRECURSED: case KA_XLOCKED | KA_RECURSED: if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) panic("Lock %s not exclusively locked @ %s:%d\n", lk->lock_object.lo_name, file, line); if (lockmgr_recursed(lk)) { if (what & KA_NOTRECURSED) panic("Lock %s recursed @ %s:%d\n", lk->lock_object.lo_name, file, line); } else if (what & KA_RECURSED) panic("Lock %s not recursed @ %s:%d\n", lk->lock_object.lo_name, file, line); break; case KA_UNLOCKED: if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) panic("Lock %s exclusively locked @ %s:%d\n", lk->lock_object.lo_name, file, line); break; default: panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, line); } } #endif #ifdef DDB int lockmgr_chain(struct thread *td, struct thread **ownerp) { const struct lock *lk; lk = td->td_wchan; if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) return (0); db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); if (lk->lk_lock & LK_SHARE) db_printf("SHARED (count %ju)\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); else db_printf("EXCL\n"); *ownerp = lockmgr_xholder(lk); return (1); } static void db_show_lockmgr(const struct lock_object *lock) { struct thread *td; const struct lock *lk; lk = (const struct lock *)lock; db_printf(" state: "); if (lk->lk_lock == LK_UNLOCKED) db_printf("UNLOCKED\n"); else if (lk->lk_lock & LK_SHARE) db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); else { td = lockmgr_xholder(lk); if (td == (struct thread *)LK_KERNPROC) db_printf("XLOCK: LK_KERNPROC\n"); else db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, td->td_tid, td->td_proc->p_pid, td->td_proc->p_comm); if (lockmgr_recursed(lk)) db_printf(" recursed: %d\n", lk->lk_recurse); } db_printf(" waiters: "); switch (lk->lk_lock & LK_ALL_WAITERS) { case LK_SHARED_WAITERS: db_printf("shared\n"); break; case LK_EXCLUSIVE_WAITERS: db_printf("exclusive\n"); break; case LK_ALL_WAITERS: db_printf("shared and exclusive\n"); break; default: db_printf("none\n"); } db_printf(" spinners: "); if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) db_printf("exclusive\n"); else db_printf("none\n"); } #endif