diff options
Diffstat (limited to 'freebsd/sys/kern/kern_lock.c')
| -rw-r--r-- | freebsd/sys/kern/kern_lock.c | 1719 |
1 files changed, 1719 insertions, 0 deletions
diff --git a/freebsd/sys/kern/kern_lock.c b/freebsd/sys/kern/kern_lock.c new file mode 100644 index 00000000..d769a185 --- /dev/null +++ b/freebsd/sys/kern/kern_lock.c @@ -0,0 +1,1719 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause-FreeBSD + * + * Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org> + * 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 <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <sys/param.h> +#include <sys/kdb.h> +#include <sys/ktr.h> +#include <sys/lock.h> +#include <sys/lock_profile.h> +#include <sys/lockmgr.h> +#include <sys/lockstat.h> +#include <sys/mutex.h> +#include <sys/proc.h> +#include <sys/sleepqueue.h> +#ifdef DEBUG_LOCKS +#include <sys/stack.h> +#endif +#include <sys/sysctl.h> +#include <sys/systm.h> + +#include <machine/cpu.h> + +#ifdef DDB +#include <ddb/ddb.h> +#endif + +#ifdef HWPMC_HOOKS +#include <sys/pmckern.h> +PMC_SOFT_DECLARE( , , lock, failed); +#endif + +CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == + (LK_ADAPTIVE | LK_NOSHARE)); +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 (_i > 0) { \ + while (_i--) \ + mtx_lock(&Giant); \ + WITNESS_RESTORE(&Giant.lock_object, Giant); \ + } \ +} while (0) +#define GIANT_SAVE() do { \ + if (mtx_owned(&Giant)) { \ + WITNESS_SAVE(&Giant.lock_object, Giant); \ + while (mtx_owned(&Giant)) { \ + _i++; \ + mtx_unlock(&Giant); \ + } \ + } \ +} while (0) + +static bool __always_inline +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 LK_CAN_ADAPT(lk, f) \ + (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ + ((f) & LK_SLEEPFAIL) == 0) + +#define lockmgr_disowned(lk) \ + (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) + +#define lockmgr_xlocked_v(v) \ + (((v) & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) + +#define lockmgr_xlocked(lk) lockmgr_xlocked_v((lk)->lk_lock) + +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 +}; + +struct lockmgr_wait { + const char *iwmesg; + int ipri; + int itimo; +}; + +static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp, + int flags, bool fp); +static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp); + +static void +lockmgr_exit(u_int flags, struct lock_object *ilk, int wakeup_swapper) +{ + struct lock_class *class; + + if (flags & LK_INTERLOCK) { + class = LOCK_CLASS(ilk); + class->lc_unlock(ilk); + } + + if (__predict_false(wakeup_swapper)) + kick_proc0(); +} + +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) +{ + + LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_READER); + 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) +{ + + LOCKSTAT_PROFILE_RELEASE_RWLOCK(lockmgr__release, lk, LOCKSTAT_WRITER); + LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, + line); + WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); + TD_LOCKS_DEC(curthread); +} + +static __inline struct thread * +lockmgr_xholder(const struct lock *lk) +{ + uintptr_t x; + + x = lk->lk_lock; + 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) + 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 int +wakeupshlk(struct lock *lk, const char *file, int line) +{ + uintptr_t v, x, orig_x; + u_int realexslp; + int queue, wakeup_swapper; + + wakeup_swapper = 0; + for (;;) { + x = lk->lk_lock; + 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 = lk->lk_lock; +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 < 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); + wakeup_swapper = + 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"); + wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, + 0, queue); + sleepq_release(&lk->lock_object); + break; + } + + lockmgr_note_shared_release(lk, file, line); + return (wakeup_swapper); +} + +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; + iflags |= flags & (LK_ADAPTIVE | 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 bool __always_inline +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. + */ + *xp = lk->lk_lock; + 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 bool __always_inline +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 __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 + + if (__predict_false(panicstr != NULL)) + 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); + for (;;) { + if (lockmgr_slock_try(lk, &x, flags, false)) + break; +#ifdef HWPMC_HOOKS + PMC_SOFT_CALL( , , lock, failed); +#endif + lock_profile_obtain_lock_failed(&lk->lock_object, + &contested, &waittime); + + /* + * If the lock is already held by curthread in + * exclusive way avoid a deadlock. + */ + if (LK_HOLDER(x) == tid) { + LOCK_LOG2(lk, + "%s: %p already held in exclusive mode", + __func__, lk); + error = EDEADLK; + break; + } + + /* + * 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 = lk->lk_lock; +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); + } + 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, 0); + return (error); +} + +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 + + if (__predict_false(panicstr != NULL)) + 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); + } + panic("%s: recursing on non recursive lockmgr %p " + "@ %s:%d\n", __func__, lk, file, line); + } + 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; + } + + 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, + &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 = lk->lk_lock; +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); + } + 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, 0); + 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, x, v; + int error = 0; + int wakeup_swapper = 0; + int op; + + if (__predict_false(panicstr != NULL)) + goto out; + + tid = (uintptr_t)curthread; + + _lockmgr_assert(lk, KA_SLOCKED, file, line); + v = lk->lk_lock; + x = v & LK_ALL_WAITERS; + v &= LK_EXCLUSIVE_SPINNERS; + + /* + * Try to switch from one shared lock to an exclusive one. + * We need to preserve waiters flags during the operation. + */ + if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, + tid | x)) { + 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; + } + + op = flags & LK_TYPE_MASK; + + /* + * In LK_TRYUPGRADE mode, do not drop the lock, + * returning EBUSY instead. + */ + if (op == LK_TRYUPGRADE) { + LOCK_LOG2(lk, "%s: %p failed the nowait upgrade", + __func__, lk); + error = EBUSY; + goto out; + } + + /* + * We have been unable to succeed in upgrading, so just + * give up the shared lock. + */ + wakeup_swapper |= wakeupshlk(lk, file, line); + error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa); + flags &= ~LK_INTERLOCK; +out: + lockmgr_exit(flags, ilk, wakeup_swapper); + return (error); +} + +int +lockmgr_lock_fast_path(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 (__predict_false(panicstr != NULL)) + 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; + 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 (lk->lk_lock == 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) + +{ + int wakeup_swapper = 0; + + if (__predict_false(panicstr != NULL)) + goto out; + + wakeup_swapper = wakeupshlk(lk, file, line); + +out: + lockmgr_exit(flags, ilk, wakeup_swapper); + 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; + int wakeup_swapper = 0; + u_int realexslp; + int queue; + + if (__predict_false(panicstr != NULL)) + 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 (LK_HOLDER(x) == LK_KERNPROC) + tid = LK_KERNPROC; + else { + 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); + + /* + * The lock is held in exclusive mode. + * If the lock is recursed also, then unrecurse it. + */ + if (lockmgr_xlocked_v(x) && lockmgr_recursed(lk)) { + LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk); + lk->lk_recurse--; + 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 = lk->lk_lock; + 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 < 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); + wakeup_swapper = 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); + wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue); + sleepq_release(&lk->lock_object); + +out: + lockmgr_exit(flags, ilk, wakeup_swapper); + return (0); +} + +int +lockmgr_unlock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk) +{ + struct lock_class *class; + uintptr_t x, tid; + const char *file; + int line; + + if (__predict_false(panicstr != NULL)) + return (0); + + file = __FILE__; + line = __LINE__; + + _lockmgr_assert(lk, KA_LOCKED, file, line); + x = lk->lk_lock; + if (__predict_true(x & LK_SHARE) != 0) { + if (lockmgr_sunlock_try(lk, &x)) { + lockmgr_note_shared_release(lk, file, line); + } else { + return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line)); + } + } else { + tid = (uintptr_t)curthread; + if (!lockmgr_recursed(lk) && + atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) { + lockmgr_note_exclusive_release(lk, file, line); + } else { + return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line)); + } + } + if (__predict_false(flags & LK_INTERLOCK)) { + class = LOCK_CLASS(ilk); + class->lc_unlock(ilk); + } + 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, wakeup_swapper; +#ifdef LOCK_PROFILING + uint64_t waittime = 0; + int contested = 0; +#endif + + if (panicstr != NULL) + 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); + } + } + + wakeup_swapper = 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 = lk->lk_lock; + 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 = lk->lk_lock; + + if (__predict_true(x & LK_SHARE) != 0) { + return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line)); + } else { + 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, + &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 = lk->lk_lock; + + /* + * 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); + wakeup_swapper = + 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"); + wakeup_swapper |= 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, + 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); + if (wakeup_swapper) + kick_proc0(); + + 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); + 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 = lk->lk_lock; + 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 = lk->lk_lock; + 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 (panicstr != NULL) + 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) +{ + 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 |