mirror of
https://github.com/freebsd/freebsd-src
synced 2024-09-30 13:44:55 +00:00
Adaptive spinning in write path with readers and writer starvation avoidance.
- Move recursion checking into rwlock inlines to free a bit for use with adaptive spinners. - Clear the RW_LOCK_WRITE_SPINNERS flag whenever the lock state changes causing write spinners to restart their loop. - Write spinners are limited by a count while readers hold the lock as there is no way to know for certain whether readers are running still. - In the read path block if there are write waiters or spinners to avoid starving writers. Use a new per-thread count, td_rw_rlocks, to skip starvation avoidance if it might cause a deadlock. - Remove or change invalid assertions in turnstiles. Reviewed by: attilio (developed parts of the patch as well) Sponsored by: Nokia
This commit is contained in:
parent
abd94b3d59
commit
5dff04c31f
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=176017
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@ -219,6 +219,17 @@ _rw_wunlock(struct rwlock *rw, const char *file, int line)
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lock_profile_release_lock(&rw->lock_object);
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__rw_wunlock(rw, curthread, file, line);
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}
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/*
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* Determines whether a new reader can acquire a lock. Succeeds if the
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* reader already owns a read lock and the lock is locked for read to
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* prevent deadlock from reader recursion. Also succeeds if the lock
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* is unlocked and has no writer waiters or spinners. Failing otherwise
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* prioritizes writers before readers.
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*/
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#define RW_CAN_READ(_rw) \
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((curthread->td_rw_rlocks && (_rw) & RW_LOCK_READ) || ((_rw) & \
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(RW_LOCK_READ | RW_LOCK_WRITE_WAITERS | RW_LOCK_WRITE_SPINNER)) == \
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RW_LOCK_READ)
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void
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_rw_rlock(struct rwlock *rw, const char *file, int line)
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@ -229,7 +240,7 @@ _rw_rlock(struct rwlock *rw, const char *file, int line)
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#endif
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uint64_t waittime = 0;
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int contested = 0;
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uintptr_t x;
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uintptr_t v;
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KASSERT(rw->rw_lock != RW_DESTROYED,
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("rw_rlock() of destroyed rwlock @ %s:%d", file, line));
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@ -238,17 +249,6 @@ _rw_rlock(struct rwlock *rw, const char *file, int line)
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rw->lock_object.lo_name, file, line));
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WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line);
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/*
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* Note that we don't make any attempt to try to block read
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* locks once a writer has blocked on the lock. The reason is
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* that we currently allow for read locks to recurse and we
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* don't keep track of all the holders of read locks. Thus, if
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* we were to block readers once a writer blocked and a reader
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* tried to recurse on their reader lock after a writer had
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* blocked we would end up in a deadlock since the reader would
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* be blocked on the writer, and the writer would be blocked
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* waiting for the reader to release its original read lock.
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*/
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for (;;) {
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/*
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* Handle the easy case. If no other thread has a write
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@ -260,22 +260,20 @@ _rw_rlock(struct rwlock *rw, const char *file, int line)
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* completely unlocked rwlock since such a lock is encoded
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* as a read lock with no waiters.
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*/
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x = rw->rw_lock;
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if (x & RW_LOCK_READ) {
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v = rw->rw_lock;
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if (RW_CAN_READ(v)) {
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/*
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* The RW_LOCK_READ_WAITERS flag should only be set
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* if another thread currently holds a write lock,
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* and in that case RW_LOCK_READ should be clear.
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* if the lock has been unlocked and write waiters
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* were present.
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*/
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MPASS((x & RW_LOCK_READ_WAITERS) == 0);
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if (atomic_cmpset_acq_ptr(&rw->rw_lock, x,
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x + RW_ONE_READER)) {
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if (atomic_cmpset_acq_ptr(&rw->rw_lock, v,
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v + RW_ONE_READER)) {
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if (LOCK_LOG_TEST(&rw->lock_object, 0))
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CTR4(KTR_LOCK,
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"%s: %p succeed %p -> %p", __func__,
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rw, (void *)x,
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(void *)(x + RW_ONE_READER));
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rw, (void *)v,
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(void *)(v + RW_ONE_READER));
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break;
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}
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cpu_spinwait();
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@ -290,32 +288,35 @@ _rw_rlock(struct rwlock *rw, const char *file, int line)
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* the owner stops running or the state of the lock
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* changes.
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*/
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owner = (struct thread *)RW_OWNER(x);
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if (TD_IS_RUNNING(owner)) {
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if (LOCK_LOG_TEST(&rw->lock_object, 0))
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CTR3(KTR_LOCK, "%s: spinning on %p held by %p",
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__func__, rw, owner);
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while ((struct thread*)RW_OWNER(rw->rw_lock) == owner &&
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TD_IS_RUNNING(owner))
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cpu_spinwait();
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continue;
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if ((v & RW_LOCK_READ) == 0) {
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owner = (struct thread *)RW_OWNER(v);
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if (TD_IS_RUNNING(owner)) {
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if (LOCK_LOG_TEST(&rw->lock_object, 0))
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CTR3(KTR_LOCK,
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"%s: spinning on %p held by %p",
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__func__, rw, owner);
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while ((struct thread*)RW_OWNER(rw->rw_lock) ==
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owner && TD_IS_RUNNING(owner))
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cpu_spinwait();
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continue;
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}
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}
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#endif
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/*
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* Okay, now it's the hard case. Some other thread already
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* has a write lock, so acquire the turnstile lock so we can
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* begin the process of blocking.
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* has a write lock or there are write waiters present,
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* acquire the turnstile lock so we can begin the process
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* of blocking.
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*/
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ts = turnstile_trywait(&rw->lock_object);
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/*
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* The lock might have been released while we spun, so
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* recheck its state and restart the loop if there is no
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* longer a write lock.
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* recheck its state and restart the loop if needed.
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*/
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x = rw->rw_lock;
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if (x & RW_LOCK_READ) {
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v = rw->rw_lock;
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if (RW_CAN_READ(v)) {
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turnstile_cancel(ts);
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cpu_spinwait();
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continue;
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@ -326,23 +327,30 @@ _rw_rlock(struct rwlock *rw, const char *file, int line)
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* If the current owner of the lock is executing on another
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* CPU quit the hard path and try to spin.
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*/
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owner = (struct thread *)RW_OWNER(x);
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if (TD_IS_RUNNING(owner)) {
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turnstile_cancel(ts);
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cpu_spinwait();
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continue;
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if ((v & RW_LOCK_READ) == 0) {
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owner = (struct thread *)RW_OWNER(v);
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if (TD_IS_RUNNING(owner)) {
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turnstile_cancel(ts);
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cpu_spinwait();
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continue;
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}
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}
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#endif
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/*
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* Ok, it's still a write lock. If the RW_LOCK_READ_WAITERS
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* flag is already set, then we can go ahead and block. If
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* it is not set then try to set it. If we fail to set it
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* drop the turnstile lock and restart the loop.
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* The lock is held in write mode or it already has waiters.
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*/
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if (!(x & RW_LOCK_READ_WAITERS)) {
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if (!atomic_cmpset_ptr(&rw->rw_lock, x,
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x | RW_LOCK_READ_WAITERS)) {
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MPASS(!RW_CAN_READ(v));
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/*
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* If the RW_LOCK_READ_WAITERS flag is already set, then
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* we can go ahead and block. If it is not set then try
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* to set it. If we fail to set it drop the turnstile
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* lock and restart the loop.
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*/
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if (!(v & RW_LOCK_READ_WAITERS)) {
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if (!atomic_cmpset_ptr(&rw->rw_lock, v,
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v | RW_LOCK_READ_WAITERS)) {
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turnstile_cancel(ts);
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cpu_spinwait();
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continue;
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LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line);
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WITNESS_LOCK(&rw->lock_object, 0, file, line);
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curthread->td_locks++;
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curthread->td_rw_rlocks++;
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}
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void
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_rw_runlock(struct rwlock *rw, const char *file, int line)
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{
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struct turnstile *ts;
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uintptr_t x;
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uintptr_t x, v, queue;
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KASSERT(rw->rw_lock != RW_DESTROYED,
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("rw_runlock() of destroyed rwlock @ %s:%d", file, line));
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_rw_assert(rw, RA_RLOCKED, file, line);
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curthread->td_locks--;
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curthread->td_rw_rlocks--;
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WITNESS_UNLOCK(&rw->lock_object, 0, file, line);
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LOCK_LOG_LOCK("RUNLOCK", &rw->lock_object, 0, 0, file, line);
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}
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continue;
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}
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/*
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* We should never have read waiters while at least one
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* thread holds a read lock. (See note above)
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*/
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KASSERT(!(x & RW_LOCK_READ_WAITERS),
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("%s: waiting readers", __func__));
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/*
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* If there aren't any waiters for a write lock, then try
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* to drop it quickly.
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*/
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if (!(x & RW_LOCK_WRITE_WAITERS)) {
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/*
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* There shouldn't be any flags set and we should
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* be the only read lock. If we fail to release
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* the single read lock, then another thread might
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* have just acquired a read lock, so go back up
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* to the multiple read locks case.
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*/
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MPASS(x == RW_READERS_LOCK(1));
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if (atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1),
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RW_UNLOCKED)) {
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if (!(x & RW_LOCK_WAITERS)) {
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MPASS((x & ~RW_LOCK_WRITE_SPINNER) ==
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RW_READERS_LOCK(1));
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if (atomic_cmpset_ptr(&rw->rw_lock, x, RW_UNLOCKED)) {
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if (LOCK_LOG_TEST(&rw->lock_object, 0))
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CTR2(KTR_LOCK, "%s: %p last succeeded",
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__func__, rw);
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}
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continue;
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}
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/*
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* There should just be one reader with one or more
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* writers waiting.
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*/
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MPASS(x == (RW_READERS_LOCK(1) | RW_LOCK_WRITE_WAITERS));
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/*
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* Ok, we know we have a waiting writer and we think we
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* are the last reader, so grab the turnstile lock.
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* Ok, we know we have waiters and we think we are the
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* last reader, so grab the turnstile lock.
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*/
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turnstile_chain_lock(&rw->lock_object);
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v = rw->rw_lock & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER);
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MPASS(v & RW_LOCK_WAITERS);
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/*
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* Try to drop our lock leaving the lock in a unlocked
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* acquired a read lock, so drop the turnstile lock and
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* restart.
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*/
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if (!atomic_cmpset_ptr(&rw->rw_lock,
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RW_READERS_LOCK(1) | RW_LOCK_WRITE_WAITERS, RW_UNLOCKED)) {
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x = RW_UNLOCKED;
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if (v & RW_LOCK_WRITE_WAITERS) {
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queue = TS_EXCLUSIVE_QUEUE;
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x |= (v & RW_LOCK_READ_WAITERS);
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} else
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queue = TS_SHARED_QUEUE;
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if (!atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v,
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x)) {
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turnstile_chain_unlock(&rw->lock_object);
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continue;
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}
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@ -489,7 +483,7 @@ _rw_runlock(struct rwlock *rw, const char *file, int line)
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*/
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ts = turnstile_lookup(&rw->lock_object);
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MPASS(ts != NULL);
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turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
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turnstile_broadcast(ts, queue);
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turnstile_unpend(ts, TS_SHARED_LOCK);
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turnstile_chain_unlock(&rw->lock_object);
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break;
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@ -508,9 +502,11 @@ _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
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struct turnstile *ts;
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#ifdef ADAPTIVE_RWLOCKS
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volatile struct thread *owner;
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int spintries = 0;
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int i;
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#endif
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uint64_t waittime = 0;
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uintptr_t v;
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uintptr_t v, x;
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int contested = 0;
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if (rw_wlocked(rw)) {
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@ -518,7 +514,6 @@ _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
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("%s: recursing but non-recursive rw %s @ %s:%d\n",
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__func__, rw->lock_object.lo_name, file, line));
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rw->rw_recurse++;
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atomic_set_ptr(&rw->rw_lock, RW_LOCK_RECURSED);
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if (LOCK_LOG_TEST(&rw->lock_object, 0))
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CTR2(KTR_LOCK, "%s: %p recursing", __func__, rw);
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return;
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@ -548,21 +543,27 @@ _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
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cpu_spinwait();
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continue;
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}
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if ((v & RW_LOCK_READ) && RW_READERS(v) && spintries < 100) {
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if (!(v & RW_LOCK_WRITE_SPINNER)) {
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if (!atomic_cmpset_ptr(&rw->rw_lock, v,
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v | RW_LOCK_WRITE_SPINNER)) {
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cpu_spinwait();
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continue;
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}
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}
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spintries++;
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for (i = 100000; i > 0; i--) {
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if ((rw->rw_lock & RW_LOCK_WRITE_SPINNER) == 0)
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break;
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cpu_spinwait();
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}
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if (i)
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continue;
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}
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#endif
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ts = turnstile_trywait(&rw->lock_object);
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v = rw->rw_lock;
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/*
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* If the lock was released while spinning on the
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* turnstile chain lock, try again.
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*/
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if (v == RW_UNLOCKED) {
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turnstile_cancel(ts);
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cpu_spinwait();
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continue;
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}
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#ifdef ADAPTIVE_RWLOCKS
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/*
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* If the current owner of the lock is executing on another
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@ -577,31 +578,24 @@ _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
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}
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}
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#endif
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/*
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* If the lock was released by a writer with both readers
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* and writers waiting and a reader hasn't woken up and
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* acquired the lock yet, rw_lock will be set to the
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* value RW_UNLOCKED | RW_LOCK_WRITE_WAITERS. If we see
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* that value, try to acquire it once. Note that we have
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* to preserve the RW_LOCK_WRITE_WAITERS flag as there are
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* other writers waiting still. If we fail, restart the
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* loop.
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* If the lock was released while waiting for the turnstile
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* chain lock retry.
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*/
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if (v == (RW_UNLOCKED | RW_LOCK_WRITE_WAITERS)) {
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if (atomic_cmpset_acq_ptr(&rw->rw_lock,
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RW_UNLOCKED | RW_LOCK_WRITE_WAITERS,
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tid | RW_LOCK_WRITE_WAITERS)) {
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turnstile_claim(ts);
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CTR2(KTR_LOCK, "%s: %p claimed by new writer",
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__func__, rw);
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x = v & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER);
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if ((v & ~x) == RW_UNLOCKED) {
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x &= ~RW_LOCK_WRITE_SPINNER;
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if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, tid | x)) {
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if (x)
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turnstile_claim(ts);
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else
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turnstile_cancel(ts);
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break;
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}
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turnstile_cancel(ts);
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cpu_spinwait();
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continue;
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}
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/*
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* If the RW_LOCK_WRITE_WAITERS flag isn't set, then try to
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* set it. If we fail to set it, then loop back and try
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|
@ -618,7 +612,6 @@ _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
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CTR2(KTR_LOCK, "%s: %p set write waiters flag",
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__func__, rw);
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}
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/*
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* We were unable to acquire the lock and the write waiters
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* flag is set, so we must block on the turnstile.
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|
@ -630,6 +623,9 @@ _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
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if (LOCK_LOG_TEST(&rw->lock_object, 0))
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CTR2(KTR_LOCK, "%s: %p resuming from turnstile",
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__func__, rw);
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#ifdef ADAPTIVE_RWLOCKS
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spintries = 0;
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#endif
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}
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lock_profile_obtain_lock_success(&rw->lock_object, contested, waittime,
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file, line);
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|
@ -648,12 +644,12 @@ _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
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int queue;
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if (rw_wlocked(rw) && rw_recursed(rw)) {
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if ((--rw->rw_recurse) == 0)
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atomic_clear_ptr(&rw->rw_lock, RW_LOCK_RECURSED);
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rw->rw_recurse--;
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if (LOCK_LOG_TEST(&rw->lock_object, 0))
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CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, rw);
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return;
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}
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v = rw->rw_lock;
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|
||||
KASSERT(rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS),
|
||||
("%s: neither of the waiter flags are set", __func__));
|
||||
|
@ -707,7 +703,7 @@ _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line)
|
|||
int
|
||||
_rw_try_upgrade(struct rwlock *rw, const char *file, int line)
|
||||
{
|
||||
uintptr_t v, tid;
|
||||
uintptr_t v, x, tid;
|
||||
struct turnstile *ts;
|
||||
int success;
|
||||
|
||||
|
@ -723,36 +719,50 @@ _rw_try_upgrade(struct rwlock *rw, const char *file, int line)
|
|||
* turnstile. So, do the simple case of no waiters first.
|
||||
*/
|
||||
tid = (uintptr_t)curthread;
|
||||
if (!(rw->rw_lock & RW_LOCK_WRITE_WAITERS)) {
|
||||
success = atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1),
|
||||
tid);
|
||||
goto out;
|
||||
}
|
||||
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 write waiters, so lock the
|
||||
* turnstile.
|
||||
*/
|
||||
ts = turnstile_trywait(&rw->lock_object);
|
||||
|
||||
/*
|
||||
* Try to switch from one reader to a writer again. This time
|
||||
* we honor the current state of the RW_LOCK_WRITE_WAITERS
|
||||
* flag. If we obtain the lock with the flag set, then claim
|
||||
* ownership of the turnstile.
|
||||
*/
|
||||
v = rw->rw_lock & RW_LOCK_WRITE_WAITERS;
|
||||
success = atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v,
|
||||
tid | v);
|
||||
if (success && v)
|
||||
turnstile_claim(ts);
|
||||
else
|
||||
/*
|
||||
* 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);
|
||||
out:
|
||||
}
|
||||
LOCK_LOG_TRY("WUPGRADE", &rw->lock_object, 0, success, file, line);
|
||||
if (success)
|
||||
if (success) {
|
||||
curthread->td_rw_rlocks--;
|
||||
WITNESS_UPGRADE(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK,
|
||||
file, line);
|
||||
}
|
||||
return (success);
|
||||
}
|
||||
|
||||
|
@ -764,6 +774,7 @@ _rw_downgrade(struct rwlock *rw, const char *file, int line)
|
|||
{
|
||||
struct turnstile *ts;
|
||||
uintptr_t tid, v;
|
||||
int rwait, wwait;
|
||||
|
||||
KASSERT(rw->rw_lock != RW_DESTROYED,
|
||||
("rw_downgrade() of destroyed rwlock @ %s:%d", file, line));
|
||||
|
@ -778,8 +789,7 @@ _rw_downgrade(struct rwlock *rw, const char *file, int line)
|
|||
/*
|
||||
* Convert from a writer to a single reader. First we handle
|
||||
* the easy case with no waiters. If there are any waiters, we
|
||||
* lock the turnstile, "disown" the lock, and awaken any read
|
||||
* waiters.
|
||||
* lock the turnstile and "disown" the lock.
|
||||
*/
|
||||
tid = (uintptr_t)curthread;
|
||||
if (atomic_cmpset_rel_ptr(&rw->rw_lock, tid, RW_READERS_LOCK(1)))
|
||||
|
@ -790,26 +800,32 @@ _rw_downgrade(struct rwlock *rw, const char *file, int line)
|
|||
* read the waiter flags without any races.
|
||||
*/
|
||||
turnstile_chain_lock(&rw->lock_object);
|
||||
v = rw->rw_lock;
|
||||
MPASS(v & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS));
|
||||
v = rw->rw_lock & RW_LOCK_WAITERS;
|
||||
rwait = v & RW_LOCK_READ_WAITERS;
|
||||
wwait = v & RW_LOCK_WRITE_WAITERS;
|
||||
MPASS(rwait | wwait);
|
||||
|
||||
/*
|
||||
* Downgrade from a write lock while preserving
|
||||
* RW_LOCK_WRITE_WAITERS and give up ownership of the
|
||||
* turnstile. If there are any read waiters, wake them up.
|
||||
* Downgrade from a write lock while preserving waiters flag
|
||||
* and give up ownership of the turnstile.
|
||||
*/
|
||||
ts = turnstile_lookup(&rw->lock_object);
|
||||
MPASS(ts != NULL);
|
||||
if (v & RW_LOCK_READ_WAITERS)
|
||||
if (!wwait)
|
||||
v &= ~RW_LOCK_READ_WAITERS;
|
||||
atomic_store_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v);
|
||||
/*
|
||||
* Wake other readers if there are no writers pending. Otherwise they
|
||||
* won't be able to acquire the lock anyway.
|
||||
*/
|
||||
if (rwait && !wwait) {
|
||||
turnstile_broadcast(ts, TS_SHARED_QUEUE);
|
||||
atomic_store_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) |
|
||||
(v & RW_LOCK_WRITE_WAITERS));
|
||||
if (v & RW_LOCK_READ_WAITERS)
|
||||
turnstile_unpend(ts, TS_EXCLUSIVE_LOCK);
|
||||
else
|
||||
} else
|
||||
turnstile_disown(ts);
|
||||
turnstile_chain_unlock(&rw->lock_object);
|
||||
out:
|
||||
curthread->td_rw_rlocks++;
|
||||
LOCK_LOG_LOCK("WDOWNGRADE", &rw->lock_object, 0, 0, file, line);
|
||||
}
|
||||
|
||||
|
|
|
@ -674,8 +674,6 @@ turnstile_wait(struct turnstile *ts, struct thread *owner, int queue)
|
|||
|
||||
td = curthread;
|
||||
mtx_assert(&ts->ts_lock, MA_OWNED);
|
||||
if (queue == TS_SHARED_QUEUE)
|
||||
MPASS(owner != NULL);
|
||||
if (owner)
|
||||
MPASS(owner->td_proc->p_magic == P_MAGIC);
|
||||
MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
|
||||
|
@ -766,8 +764,7 @@ turnstile_signal(struct turnstile *ts, int queue)
|
|||
MPASS(ts != NULL);
|
||||
mtx_assert(&ts->ts_lock, MA_OWNED);
|
||||
MPASS(curthread->td_proc->p_magic == P_MAGIC);
|
||||
MPASS(ts->ts_owner == curthread ||
|
||||
(queue == TS_EXCLUSIVE_QUEUE && ts->ts_owner == NULL));
|
||||
MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
|
||||
MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
|
||||
|
||||
/*
|
||||
|
@ -818,8 +815,7 @@ turnstile_broadcast(struct turnstile *ts, int queue)
|
|||
MPASS(ts != NULL);
|
||||
mtx_assert(&ts->ts_lock, MA_OWNED);
|
||||
MPASS(curthread->td_proc->p_magic == P_MAGIC);
|
||||
MPASS(ts->ts_owner == curthread ||
|
||||
(queue == TS_EXCLUSIVE_QUEUE && ts->ts_owner == NULL));
|
||||
MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
|
||||
/*
|
||||
* We must have the chain locked so that we can remove the empty
|
||||
* turnstile from the hash queue.
|
||||
|
@ -869,8 +865,7 @@ turnstile_unpend(struct turnstile *ts, int owner_type)
|
|||
|
||||
MPASS(ts != NULL);
|
||||
mtx_assert(&ts->ts_lock, MA_OWNED);
|
||||
MPASS(ts->ts_owner == curthread ||
|
||||
(owner_type == TS_SHARED_LOCK && ts->ts_owner == NULL));
|
||||
MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
|
||||
MPASS(!TAILQ_EMPTY(&ts->ts_pending));
|
||||
|
||||
/*
|
||||
|
|
|
@ -229,8 +229,9 @@ struct thread {
|
|||
u_char td_lastcpu; /* (t) Last cpu we were on. */
|
||||
u_char td_oncpu; /* (t) Which cpu we are on. */
|
||||
volatile u_char td_owepreempt; /* (k*) Preempt on last critical_exit */
|
||||
short td_locks; /* (k) Count of non-spin locks. */
|
||||
u_char td_tsqueue; /* (t) Turnstile queue blocked on. */
|
||||
short td_locks; /* (k) Count of non-spin locks. */
|
||||
short td_rw_rlocks; /* (k) count of rwlock read locks. */
|
||||
struct turnstile *td_blocked; /* (t) Lock thread is blocked on. */
|
||||
const char *td_lockname; /* (t) Name of lock blocked on. */
|
||||
LIST_HEAD(, turnstile) td_contested; /* (q) Contested locks. */
|
||||
|
|
|
@ -66,10 +66,11 @@
|
|||
#define RW_LOCK_READ 0x01
|
||||
#define RW_LOCK_READ_WAITERS 0x02
|
||||
#define RW_LOCK_WRITE_WAITERS 0x04
|
||||
#define RW_LOCK_RECURSED 0x08
|
||||
#define RW_LOCK_WRITE_SPINNER 0x08
|
||||
#define RW_LOCK_FLAGMASK \
|
||||
(RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \
|
||||
RW_LOCK_RECURSED)
|
||||
RW_LOCK_WRITE_SPINNER)
|
||||
#define RW_LOCK_WAITERS (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
|
||||
|
||||
#define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
|
||||
#define RW_READERS_SHIFT 4
|
||||
|
@ -113,7 +114,9 @@
|
|||
#define __rw_wunlock(rw, tid, file, line) do { \
|
||||
uintptr_t _tid = (uintptr_t)(tid); \
|
||||
\
|
||||
if (!_rw_write_unlock((rw), _tid)) \
|
||||
if ((rw)->rw_recurse) \
|
||||
(rw)->rw_recurse--; \
|
||||
else if (!_rw_write_unlock((rw), _tid)) \
|
||||
_rw_wunlock_hard((rw), _tid, (file), (line)); \
|
||||
} while (0)
|
||||
|
||||
|
|
Loading…
Reference in a new issue