示例#1
0
void
_rm_wlock(struct rmlock *rm)
{
	struct rm_priotracker *prio;
	struct turnstile *ts;
	cpuset_t readcpus;

	if (SCHEDULER_STOPPED())
		return;

	if (rm->lock_object.lo_flags & LO_SLEEPABLE)
		sx_xlock(&rm->rm_lock_sx);
	else
		mtx_lock(&rm->rm_lock_mtx);

	if (CPU_CMP(&rm->rm_writecpus, &all_cpus)) {
		/* Get all read tokens back */
		readcpus = all_cpus;
		CPU_NAND(&readcpus, &rm->rm_writecpus);
		rm->rm_writecpus = all_cpus;

		/*
		 * Assumes rm->rm_writecpus update is visible on other CPUs
		 * before rm_cleanIPI is called.
		 */
#ifdef SMP
		smp_rendezvous_cpus(readcpus,
		    smp_no_rendevous_barrier,
		    rm_cleanIPI,
		    smp_no_rendevous_barrier,
		    rm);

#else
		rm_cleanIPI(rm);
#endif

		mtx_lock_spin(&rm_spinlock);
		while ((prio = LIST_FIRST(&rm->rm_activeReaders)) != NULL) {
			ts = turnstile_trywait(&rm->lock_object);
			prio->rmp_flags = RMPF_ONQUEUE | RMPF_SIGNAL;
			mtx_unlock_spin(&rm_spinlock);
			turnstile_wait(ts, prio->rmp_thread,
			    TS_EXCLUSIVE_QUEUE);
			mtx_lock_spin(&rm_spinlock);
		}
		mtx_unlock_spin(&rm_spinlock);
	}
}
示例#2
0
/*
 * _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)
{
	struct turnstile *ts;
	uintptr_t v;
#ifdef ADAPTIVE_MUTEXES
	volatile struct thread *owner;
#endif
#ifdef KTR
	int cont_logged = 0;
#endif
#ifdef LOCK_PROFILING
	int contested = 0;
	uint64_t waittime = 0;
#endif
#ifdef KDTRACE_HOOKS
	uint64_t spin_cnt = 0;
	uint64_t sleep_cnt = 0;
	int64_t sleep_time = 0;
#endif

	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;
	}

	lock_profile_obtain_lock_failed(&m->lock_object,
		    &contested, &waittime);
	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)) {
#ifdef KDTRACE_HOOKS
		spin_cnt++;
#endif
#ifdef ADAPTIVE_MUTEXES
		/*
		 * If the owner is running on another CPU, spin until the
		 * owner stops running or the state of the lock changes.
		 */
		v = m->mtx_lock;
		if (v != MTX_UNOWNED) {
			owner = (struct thread *)(v & ~MTX_FLAGMASK);
			if (TD_IS_RUNNING(owner)) {
				if (LOCK_LOG_TEST(&m->lock_object, 0))
					CTR3(KTR_LOCK,
					    "%s: spinning on %p held by %p",
					    __func__, m, owner);
				while (mtx_owner(m) == owner &&
				    TD_IS_RUNNING(owner)) {
					cpu_spinwait();
#ifdef KDTRACE_HOOKS
					spin_cnt++;
#endif
				}
				continue;
			}
		}
#endif

		ts = turnstile_trywait(&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_cancel(ts);
			continue;
		}

#ifdef ADAPTIVE_MUTEXES
		/*
		 * The current lock owner might have started executing
		 * on another CPU (or the lock could have changed
		 * owners) while we were waiting on the turnstile
		 * chain lock.  If so, drop the turnstile lock and try
		 * again.
		 */
		owner = (struct thread *)(v & ~MTX_FLAGMASK);
		if (TD_IS_RUNNING(owner)) {
			turnstile_cancel(ts);
			continue;
		}
#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_cancel(ts);
			continue;
		}

		/*
		 * 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.
		 */
#ifdef KDTRACE_HOOKS
		sleep_time -= lockstat_nsecs();
#endif
		turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE);
#ifdef KDTRACE_HOOKS
		sleep_time += lockstat_nsecs();
		sleep_cnt++;
#endif
	}
#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
	LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, m, contested,
	    waittime, file, line);
#ifdef KDTRACE_HOOKS
	if (sleep_time)
		LOCKSTAT_RECORD1(LS_MTX_LOCK_BLOCK, m, sleep_time);

	/*
	 * Only record the loops spinning and not sleeping. 
	 */
	if (spin_cnt > sleep_cnt)
		LOCKSTAT_RECORD1(LS_MTX_LOCK_SPIN, m, (spin_cnt - sleep_cnt));
#endif
}
示例#3
0
/*
 * This function is called when we are unable to obtain a write lock on the
 * first try.  This means that at least one other thread holds either a
 * read or write lock.
 */
void
__rw_wlock_hard(volatile uintptr_t *c, uintptr_t tid, const char *file,
    int line)
{
	struct rwlock *rw;
	struct turnstile *ts;
#ifdef ADAPTIVE_RWLOCKS
	volatile struct thread *owner;
	int spintries = 0;
	int i;
#endif
	uintptr_t v, x;
#ifdef LOCK_PROFILING
	uint64_t waittime = 0;
	int contested = 0;
#endif
#ifdef KDTRACE_HOOKS
	uintptr_t state;
	uint64_t spin_cnt = 0;
	uint64_t sleep_cnt = 0;
	int64_t sleep_time = 0;
	int64_t all_time = 0;
#endif

	if (SCHEDULER_STOPPED())
		return;

	rw = rwlock2rw(c);

	if (rw_wlocked(rw)) {
		KASSERT(rw->lock_object.lo_flags & LO_RECURSABLE,
		    ("%s: recursing but non-recursive rw %s @ %s:%d\n",
		    __func__, rw->lock_object.lo_name, file, line));
		rw->rw_recurse++;
		if (LOCK_LOG_TEST(&rw->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p recursing", __func__, rw);
		return;
	}

	if (LOCK_LOG_TEST(&rw->lock_object, 0))
		CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__,
		    rw->lock_object.lo_name, (void *)rw->rw_lock, file, line);

#ifdef KDTRACE_HOOKS
	all_time -= lockstat_nsecs(&rw->lock_object);
	state = rw->rw_lock;
#endif
	while (!_rw_write_lock(rw, tid)) {
#ifdef KDTRACE_HOOKS
		spin_cnt++;
#endif
#ifdef HWPMC_HOOKS
		PMC_SOFT_CALL( , , lock, failed);
#endif
		lock_profile_obtain_lock_failed(&rw->lock_object,
		    &contested, &waittime);
#ifdef ADAPTIVE_RWLOCKS
		/*
		 * If the lock is write locked and the owner is
		 * running on another CPU, spin until the owner stops
		 * running or the state of the lock changes.
		 */
		v = rw->rw_lock;
		owner = (struct thread *)RW_OWNER(v);
		if (!(v & RW_LOCK_READ) && TD_IS_RUNNING(owner)) {
			if (LOCK_LOG_TEST(&rw->lock_object, 0))
				CTR3(KTR_LOCK, "%s: spinning on %p held by %p",
				    __func__, rw, owner);
			KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread),
			    "spinning", "lockname:\"%s\"",
			    rw->lock_object.lo_name);
			while ((struct thread*)RW_OWNER(rw->rw_lock) == owner &&
			    TD_IS_RUNNING(owner)) {
				cpu_spinwait();
#ifdef KDTRACE_HOOKS
				spin_cnt++;
#endif
			}
			KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread),
			    "running");
			continue;
		}
		if ((v & RW_LOCK_READ) && RW_READERS(v) &&
		    spintries < rowner_retries) {
			if (!(v & RW_LOCK_WRITE_SPINNER)) {
				if (!atomic_cmpset_ptr(&rw->rw_lock, v,
				    v | RW_LOCK_WRITE_SPINNER)) {
					continue;
				}
			}
			spintries++;
			KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread),
			    "spinning", "lockname:\"%s\"",
			    rw->lock_object.lo_name);
			for (i = 0; i < rowner_loops; i++) {
				if ((rw->rw_lock & RW_LOCK_WRITE_SPINNER) == 0)
					break;
				cpu_spinwait();
			}
			KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread),
			    "running");
#ifdef KDTRACE_HOOKS
			spin_cnt += rowner_loops - i;
#endif
			if (i != rowner_loops)
				continue;
		}
#endif
		ts = turnstile_trywait(&rw->lock_object);
		v = rw->rw_lock;

#ifdef ADAPTIVE_RWLOCKS
		/*
		 * The current lock owner might have started executing
		 * on another CPU (or the lock could have changed
		 * owners) while we were waiting on the turnstile
		 * chain lock.  If so, drop the turnstile lock and try
		 * again.
		 */
		if (!(v & RW_LOCK_READ)) {
			owner = (struct thread *)RW_OWNER(v);
			if (TD_IS_RUNNING(owner)) {
				turnstile_cancel(ts);
				continue;
			}
		}
#endif
		/*
		 * Check for the waiters flags about this rwlock.
		 * If the lock was released, without maintain any pending
		 * waiters queue, simply try to acquire it.
		 * If a pending waiters queue is present, claim the lock
		 * ownership and maintain the pending queue.
		 */
		x = v & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER);
		if ((v & ~x) == RW_UNLOCKED) {
			x &= ~RW_LOCK_WRITE_SPINNER;
			if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, tid | x)) {
				if (x)
					turnstile_claim(ts);
				else
					turnstile_cancel(ts);
				break;
			}
			turnstile_cancel(ts);
			continue;
		}
		/*
		 * If the RW_LOCK_WRITE_WAITERS flag isn't set, then try to
		 * set it.  If we fail to set it, then loop back and try
		 * again.
		 */
		if (!(v & RW_LOCK_WRITE_WAITERS)) {
			if (!atomic_cmpset_ptr(&rw->rw_lock, v,
			    v | RW_LOCK_WRITE_WAITERS)) {
				turnstile_cancel(ts);
				continue;
			}
			if (LOCK_LOG_TEST(&rw->lock_object, 0))
				CTR2(KTR_LOCK, "%s: %p set write waiters flag",
				    __func__, rw);
		}
		/*
		 * We were unable to acquire the lock and the write waiters
		 * flag is set, so we must block on the turnstile.
		 */
		if (LOCK_LOG_TEST(&rw->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__,
			    rw);
#ifdef KDTRACE_HOOKS
		sleep_time -= lockstat_nsecs(&rw->lock_object);
#endif
		turnstile_wait(ts, rw_owner(rw), TS_EXCLUSIVE_QUEUE);
#ifdef KDTRACE_HOOKS
		sleep_time += lockstat_nsecs(&rw->lock_object);
		sleep_cnt++;
#endif
		if (LOCK_LOG_TEST(&rw->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p resuming from turnstile",
			    __func__, rw);
#ifdef ADAPTIVE_RWLOCKS
		spintries = 0;
#endif
	}
#ifdef KDTRACE_HOOKS
	all_time += lockstat_nsecs(&rw->lock_object);
	if (sleep_time)
		LOCKSTAT_RECORD4(rw__block, rw, sleep_time,
		    LOCKSTAT_WRITER, (state & RW_LOCK_READ) == 0,
		    (state & RW_LOCK_READ) == 0 ? 0 : RW_READERS(state));

	/* Record only the loops spinning and not sleeping. */
	if (spin_cnt > sleep_cnt)
		LOCKSTAT_RECORD4(rw__spin, rw, all_time - sleep_time,
		    LOCKSTAT_READER, (state & RW_LOCK_READ) == 0,
		    (state & RW_LOCK_READ) == 0 ? 0 : RW_READERS(state));
#endif
	LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(rw__acquire, rw, contested,
	    waittime, file, line, LOCKSTAT_WRITER);
}
示例#4
0
void
__rw_rlock(volatile uintptr_t *c, const char *file, int line)
{
	struct rwlock *rw;
	struct turnstile *ts;
#ifdef ADAPTIVE_RWLOCKS
	volatile struct thread *owner;
	int spintries = 0;
	int i;
#endif
#ifdef LOCK_PROFILING
	uint64_t waittime = 0;
	int contested = 0;
#endif
	uintptr_t v;
#ifdef KDTRACE_HOOKS
	uintptr_t state;
	uint64_t spin_cnt = 0;
	uint64_t sleep_cnt = 0;
	int64_t sleep_time = 0;
	int64_t all_time = 0;
#endif

	if (SCHEDULER_STOPPED())
		return;

	rw = rwlock2rw(c);

	KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
	    ("rw_rlock() by idle thread %p on rwlock %s @ %s:%d",
	    curthread, rw->lock_object.lo_name, file, line));
	KASSERT(rw->rw_lock != RW_DESTROYED,
	    ("rw_rlock() of destroyed rwlock @ %s:%d", file, line));
	KASSERT(rw_wowner(rw) != curthread,
	    ("rw_rlock: wlock already held for %s @ %s:%d",
	    rw->lock_object.lo_name, file, line));
	WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line, NULL);

#ifdef KDTRACE_HOOKS
	all_time -= lockstat_nsecs(&rw->lock_object);
	state = rw->rw_lock;
#endif
	for (;;) {
		/*
		 * Handle the easy case.  If no other thread has a write
		 * lock, then try to bump up the count of read locks.  Note
		 * that we have to preserve the current state of the
		 * RW_LOCK_WRITE_WAITERS flag.  If we fail to acquire a
		 * read lock, then rw_lock must have changed, so restart
		 * the loop.  Note that this handles the case of a
		 * completely unlocked rwlock since such a lock is encoded
		 * as a read lock with no waiters.
		 */
		v = rw->rw_lock;
		if (RW_CAN_READ(v)) {
			/*
			 * The RW_LOCK_READ_WAITERS flag should only be set
			 * if the lock has been unlocked and write waiters
			 * were present.
			 */
			if (atomic_cmpset_acq_ptr(&rw->rw_lock, v,
			    v + RW_ONE_READER)) {
				if (LOCK_LOG_TEST(&rw->lock_object, 0))
					CTR4(KTR_LOCK,
					    "%s: %p succeed %p -> %p", __func__,
					    rw, (void *)v,
					    (void *)(v + RW_ONE_READER));
				break;
			}
			continue;
		}
#ifdef KDTRACE_HOOKS
		spin_cnt++;
#endif
#ifdef HWPMC_HOOKS
		PMC_SOFT_CALL( , , lock, failed);
#endif
		lock_profile_obtain_lock_failed(&rw->lock_object,
		    &contested, &waittime);

#ifdef ADAPTIVE_RWLOCKS
		/*
		 * If the owner is running on another CPU, spin until
		 * the owner stops running or the state of the lock
		 * changes.
		 */
		if ((v & RW_LOCK_READ) == 0) {
			owner = (struct thread *)RW_OWNER(v);
			if (TD_IS_RUNNING(owner)) {
				if (LOCK_LOG_TEST(&rw->lock_object, 0))
					CTR3(KTR_LOCK,
					    "%s: spinning on %p held by %p",
					    __func__, rw, owner);
				KTR_STATE1(KTR_SCHED, "thread",
				    sched_tdname(curthread), "spinning",
				    "lockname:\"%s\"", rw->lock_object.lo_name);
				while ((struct thread*)RW_OWNER(rw->rw_lock) ==
				    owner && TD_IS_RUNNING(owner)) {
					cpu_spinwait();
#ifdef KDTRACE_HOOKS
					spin_cnt++;
#endif
				}
				KTR_STATE0(KTR_SCHED, "thread",
				    sched_tdname(curthread), "running");
				continue;
			}
		} else if (spintries < rowner_retries) {
			spintries++;
			KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread),
			    "spinning", "lockname:\"%s\"",
			    rw->lock_object.lo_name);
			for (i = 0; i < rowner_loops; i++) {
				v = rw->rw_lock;
				if ((v & RW_LOCK_READ) == 0 || RW_CAN_READ(v))
					break;
				cpu_spinwait();
			}
#ifdef KDTRACE_HOOKS
			spin_cnt += rowner_loops - i;
#endif
			KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread),
			    "running");
			if (i != rowner_loops)
				continue;
		}
#endif

		/*
		 * Okay, now it's the hard case.  Some other thread already
		 * has a write lock or there are write waiters present,
		 * acquire the turnstile lock so we can begin the process
		 * of blocking.
		 */
		ts = turnstile_trywait(&rw->lock_object);

		/*
		 * The lock might have been released while we spun, so
		 * recheck its state and restart the loop if needed.
		 */
		v = rw->rw_lock;
		if (RW_CAN_READ(v)) {
			turnstile_cancel(ts);
			continue;
		}

#ifdef ADAPTIVE_RWLOCKS
		/*
		 * The current lock owner might have started executing
		 * on another CPU (or the lock could have changed
		 * owners) while we were waiting on the turnstile
		 * chain lock.  If so, drop the turnstile lock and try
		 * again.
		 */
		if ((v & RW_LOCK_READ) == 0) {
			owner = (struct thread *)RW_OWNER(v);
			if (TD_IS_RUNNING(owner)) {
				turnstile_cancel(ts);
				continue;
			}
		}
#endif

		/*
		 * The lock is held in write mode or it already has waiters.
		 */
		MPASS(!RW_CAN_READ(v));

		/*
		 * If the RW_LOCK_READ_WAITERS flag is already set, then
		 * we can go ahead and block.  If it is not set then try
		 * to set it.  If we fail to set it drop the turnstile
		 * lock and restart the loop.
		 */
		if (!(v & RW_LOCK_READ_WAITERS)) {
			if (!atomic_cmpset_ptr(&rw->rw_lock, v,
			    v | RW_LOCK_READ_WAITERS)) {
				turnstile_cancel(ts);
				continue;
			}
			if (LOCK_LOG_TEST(&rw->lock_object, 0))
				CTR2(KTR_LOCK, "%s: %p set read waiters flag",
				    __func__, rw);
		}

		/*
		 * We were unable to acquire the lock and the read waiters
		 * flag is set, so we must block on the turnstile.
		 */
		if (LOCK_LOG_TEST(&rw->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__,
			    rw);
#ifdef KDTRACE_HOOKS
		sleep_time -= lockstat_nsecs(&rw->lock_object);
#endif
		turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE);
#ifdef KDTRACE_HOOKS
		sleep_time += lockstat_nsecs(&rw->lock_object);
		sleep_cnt++;
#endif
		if (LOCK_LOG_TEST(&rw->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p resuming from turnstile",
			    __func__, rw);
	}
#ifdef KDTRACE_HOOKS
	all_time += lockstat_nsecs(&rw->lock_object);
	if (sleep_time)
		LOCKSTAT_RECORD4(rw__block, rw, sleep_time,
		    LOCKSTAT_READER, (state & RW_LOCK_READ) == 0,
		    (state & RW_LOCK_READ) == 0 ? 0 : RW_READERS(state));

	/* Record only the loops spinning and not sleeping. */
	if (spin_cnt > sleep_cnt)
		LOCKSTAT_RECORD4(rw__spin, rw, all_time - sleep_time,
		    LOCKSTAT_READER, (state & RW_LOCK_READ) == 0,
		    (state & RW_LOCK_READ) == 0 ? 0 : RW_READERS(state));
#endif
	/*
	 * TODO: acquire "owner of record" here.  Here be turnstile dragons
	 * however.  turnstiles don't like owners changing between calls to
	 * turnstile_wait() currently.
	 */
	LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(rw__acquire, rw, contested,
	    waittime, file, line, LOCKSTAT_READER);
	LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line);
	WITNESS_LOCK(&rw->lock_object, 0, file, line);
	curthread->td_locks++;
	curthread->td_rw_rlocks++;
}
示例#5
0
/*
 * Attempt to do a non-blocking upgrade from a read lock to a write
 * lock.  This will only succeed if this thread holds a single read
 * lock.  Returns true if the upgrade succeeded and false otherwise.
 */
int
__rw_try_upgrade(volatile uintptr_t *c, const char *file, int line)
{
	struct rwlock *rw;
	uintptr_t v, x, tid;
	struct turnstile *ts;
	int success;

	if (SCHEDULER_STOPPED())
		return (1);

	rw = rwlock2rw(c);

	KASSERT(rw->rw_lock != RW_DESTROYED,
	    ("rw_try_upgrade() of destroyed rwlock @ %s:%d", file, line));
	__rw_assert(c, RA_RLOCKED, file, line);

	/*
	 * Attempt to switch from one reader to a writer.  If there
	 * are any write waiters, then we will have to lock the
	 * turnstile first to prevent races with another writer
	 * calling turnstile_wait() before we have claimed this
	 * turnstile.  So, do the simple case of no waiters first.
	 */
	tid = (uintptr_t)curthread;
	success = 0;
	for (;;) {
		v = rw->rw_lock;
		if (RW_READERS(v) > 1)
			break;
		if (!(v & RW_LOCK_WAITERS)) {
			success = atomic_cmpset_ptr(&rw->rw_lock, v, tid);
			if (!success)
				continue;
			break;
		}

		/*
		 * Ok, we think we have waiters, so lock the turnstile.
		 */
		ts = turnstile_trywait(&rw->lock_object);
		v = rw->rw_lock;
		if (RW_READERS(v) > 1) {
			turnstile_cancel(ts);
			break;
		}
		/*
		 * Try to switch from one reader to a writer again.  This time
		 * we honor the current state of the waiters flags.
		 * If we obtain the lock with the flags set, then claim
		 * ownership of the turnstile.
		 */
		x = rw->rw_lock & RW_LOCK_WAITERS;
		success = atomic_cmpset_ptr(&rw->rw_lock, v, tid | x);
		if (success) {
			if (x)
				turnstile_claim(ts);
			else
				turnstile_cancel(ts);
			break;
		}
		turnstile_cancel(ts);
	}
	LOCK_LOG_TRY("WUPGRADE", &rw->lock_object, 0, success, file, line);
	if (success) {
		curthread->td_rw_rlocks--;
		WITNESS_UPGRADE(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK,
		    file, line);
		LOCKSTAT_RECORD0(rw__upgrade, rw);
	}
	return (success);
}
示例#6
0
/*
 * __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(volatile uintptr_t *c, uintptr_t tid, int opts,
    const char *file, int line)
{
	struct mtx *m;
	struct turnstile *ts;
	uintptr_t v;
#ifdef ADAPTIVE_MUTEXES
	volatile struct thread *owner;
#endif
#ifdef KTR
	int cont_logged = 0;
#endif
#ifdef LOCK_PROFILING
	int contested = 0;
	uint64_t waittime = 0;
#endif
#if defined(ADAPTIVE_MUTEXES) || defined(KDTRACE_HOOKS)
	struct lock_delay_arg lda;
#endif
#ifdef KDTRACE_HOOKS
	u_int sleep_cnt = 0;
	int64_t sleep_time = 0;
	int64_t all_time = 0;
#endif

	if (SCHEDULER_STOPPED())
		return;

#if defined(ADAPTIVE_MUTEXES)
	lock_delay_arg_init(&lda, &mtx_delay);
#elif defined(KDTRACE_HOOKS)
	lock_delay_arg_init(&lda, NULL);
#endif
	m = mtxlock2mtx(c);

	if (mtx_owned(m)) {
		KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
		    (opts & MTX_RECURSE) != 0,
	    ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
		    m->lock_object.lo_name, file, line));
		opts &= ~MTX_RECURSE;
		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;
	}
	opts &= ~MTX_RECURSE;

#ifdef HWPMC_HOOKS
	PMC_SOFT_CALL( , , lock, failed);
#endif
	lock_profile_obtain_lock_failed(&m->lock_object,
		    &contested, &waittime);
	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);
#ifdef KDTRACE_HOOKS
	all_time -= lockstat_nsecs(&m->lock_object);
#endif

	for (;;) {
		if (m->mtx_lock == MTX_UNOWNED && _mtx_obtain_lock(m, tid))
			break;
#ifdef KDTRACE_HOOKS
		lda.spin_cnt++;
#endif
#ifdef ADAPTIVE_MUTEXES
		/*
		 * If the owner is running on another CPU, spin until the
		 * owner stops running or the state of the lock changes.
		 */
		v = m->mtx_lock;
		if (v != MTX_UNOWNED) {
			owner = (struct thread *)(v & ~MTX_FLAGMASK);
			if (TD_IS_RUNNING(owner)) {
				if (LOCK_LOG_TEST(&m->lock_object, 0))
					CTR3(KTR_LOCK,
					    "%s: spinning on %p held by %p",
					    __func__, m, owner);
				KTR_STATE1(KTR_SCHED, "thread",
				    sched_tdname((struct thread *)tid),
				    "spinning", "lockname:\"%s\"",
				    m->lock_object.lo_name);
				while (mtx_owner(m) == owner &&
				    TD_IS_RUNNING(owner))
					lock_delay(&lda);
				KTR_STATE0(KTR_SCHED, "thread",
				    sched_tdname((struct thread *)tid),
				    "running");
				continue;
			}
		}
#endif

		ts = turnstile_trywait(&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_cancel(ts);
			continue;
		}

#ifdef ADAPTIVE_MUTEXES
		/*
		 * The current lock owner might have started executing
		 * on another CPU (or the lock could have changed
		 * owners) while we were waiting on the turnstile
		 * chain lock.  If so, drop the turnstile lock and try
		 * again.
		 */
		owner = (struct thread *)(v & ~MTX_FLAGMASK);
		if (TD_IS_RUNNING(owner)) {
			turnstile_cancel(ts);
			continue;
		}
#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_cancel(ts);
			continue;
		}

		/*
		 * 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.
		 */
#ifdef KDTRACE_HOOKS
		sleep_time -= lockstat_nsecs(&m->lock_object);
#endif
		turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE);
#ifdef KDTRACE_HOOKS
		sleep_time += lockstat_nsecs(&m->lock_object);
		sleep_cnt++;
#endif
	}
#ifdef KDTRACE_HOOKS
	all_time += lockstat_nsecs(&m->lock_object);
#endif
#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
	LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, m, contested,
	    waittime, file, line);
#ifdef KDTRACE_HOOKS
	if (sleep_time)
		LOCKSTAT_RECORD1(adaptive__block, m, sleep_time);

	/*
	 * Only record the loops spinning and not sleeping. 
	 */
	if (lda.spin_cnt > sleep_cnt)
		LOCKSTAT_RECORD1(adaptive__spin, m, all_time - sleep_time);
#endif
}