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sx: switch to fcmpset

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Discussed with:	jhb
Tested by:	pho (previous version)
This commit is contained in:
Mateusz Guzik 2017-02-05 04:54:20 +00:00
parent c84f347985
commit fa47404353
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=313271
2 changed files with 14 additions and 21 deletions
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23
sys/kern/kern_sx.c
View File

@ -530,15 +530,14 @@ sx_downgrade_(struct sx *sx, const char *file, int line)
* accessible from at least sx.h. * accessible from at least sx.h.
*/ */
int int
_sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file, _sx_xlock_hard(struct sx *sx, uintptr_t x, uintptr_t tid, int opts,
int line) const char *file, int line)
{ {
GIANT_DECLARE; GIANT_DECLARE;
#ifdef ADAPTIVE_SX #ifdef ADAPTIVE_SX
volatile struct thread *owner; volatile struct thread *owner;
u_int i, spintries = 0; u_int i, spintries = 0;
#endif #endif
uintptr_t x;
#ifdef LOCK_PROFILING #ifdef LOCK_PROFILING
uint64_t waittime = 0; uint64_t waittime = 0;
int contested = 0; int contested = 0;
@ -563,8 +562,6 @@ _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file,
lock_delay_arg_init(&lda, NULL); lock_delay_arg_init(&lda, NULL);
#endif #endif
x = SX_READ_VALUE(sx);
/* If we already hold an exclusive lock, then recurse. */ /* If we already hold an exclusive lock, then recurse. */
if (__predict_false(lv_sx_owner(x) == (struct thread *)tid)) { if (__predict_false(lv_sx_owner(x) == (struct thread *)tid)) {
KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0, KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0,
@ -587,9 +584,8 @@ _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file,
#endif #endif
for (;;) { for (;;) {
if (x == SX_LOCK_UNLOCKED) { if (x == SX_LOCK_UNLOCKED) {
if (atomic_cmpset_acq_ptr(&sx->sx_lock, x, tid)) if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x, tid))
break; break;
x = SX_READ_VALUE(sx);
continue; continue;
} }
#ifdef KDTRACE_HOOKS #ifdef KDTRACE_HOOKS
@ -902,7 +898,7 @@ _sx_slock_hard(struct sx *sx, int opts, const char *file, int line)
*/ */
if (x & SX_LOCK_SHARED) { if (x & SX_LOCK_SHARED) {
MPASS(!(x & SX_LOCK_SHARED_WAITERS)); MPASS(!(x & SX_LOCK_SHARED_WAITERS));
if (atomic_cmpset_acq_ptr(&sx->sx_lock, x, if (atomic_fcmpset_acq_ptr(&sx->sx_lock, &x,
x + SX_ONE_SHARER)) { x + SX_ONE_SHARER)) {
if (LOCK_LOG_TEST(&sx->lock_object, 0)) if (LOCK_LOG_TEST(&sx->lock_object, 0))
CTR4(KTR_LOCK, CTR4(KTR_LOCK,
@ -911,7 +907,6 @@ _sx_slock_hard(struct sx *sx, int opts, const char *file, int line)
(void *)(x + SX_ONE_SHARER)); (void *)(x + SX_ONE_SHARER));
break; break;
} }
x = SX_READ_VALUE(sx);
continue; continue;
} }
#ifdef KDTRACE_HOOKS #ifdef KDTRACE_HOOKS
@ -1085,7 +1080,7 @@ _sx_sunlock_hard(struct sx *sx, const char *file, int line)
* so, just drop one and return. * so, just drop one and return.
*/ */
if (SX_SHARERS(x) > 1) { if (SX_SHARERS(x) > 1) {
if (atomic_cmpset_rel_ptr(&sx->sx_lock, x, if (atomic_fcmpset_rel_ptr(&sx->sx_lock, &x,
x - SX_ONE_SHARER)) { x - SX_ONE_SHARER)) {
if (LOCK_LOG_TEST(&sx->lock_object, 0)) if (LOCK_LOG_TEST(&sx->lock_object, 0))
CTR4(KTR_LOCK, CTR4(KTR_LOCK,
@ -1094,8 +1089,6 @@ _sx_sunlock_hard(struct sx *sx, const char *file, int line)
(void *)(x - SX_ONE_SHARER)); (void *)(x - SX_ONE_SHARER));
break; break;
} }
x = SX_READ_VALUE(sx);
continue; continue;
} }
@ -1105,14 +1098,14 @@ _sx_sunlock_hard(struct sx *sx, const char *file, int line)
*/ */
if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) {
MPASS(x == SX_SHARERS_LOCK(1)); MPASS(x == SX_SHARERS_LOCK(1));
if (atomic_cmpset_rel_ptr(&sx->sx_lock, x = SX_SHARERS_LOCK(1);
SX_SHARERS_LOCK(1), SX_LOCK_UNLOCKED)) { if (atomic_fcmpset_rel_ptr(&sx->sx_lock,
&x, SX_LOCK_UNLOCKED)) {
if (LOCK_LOG_TEST(&sx->lock_object, 0)) if (LOCK_LOG_TEST(&sx->lock_object, 0))
CTR2(KTR_LOCK, "%s: %p last succeeded", CTR2(KTR_LOCK, "%s: %p last succeeded",
__func__, sx); __func__, sx);
break; break;
} }
x = SX_READ_VALUE(sx);
continue; continue;
} }

12
sys/sys/sx.h
View File

@ -109,7 +109,7 @@ int _sx_slock(struct sx *sx, int opts, const char *file, int line);
int _sx_xlock(struct sx *sx, int opts, const char *file, int line); int _sx_xlock(struct sx *sx, int opts, const char *file, int line);
void _sx_sunlock(struct sx *sx, const char *file, int line); void _sx_sunlock(struct sx *sx, const char *file, int line);
void _sx_xunlock(struct sx *sx, const char *file, int line); void _sx_xunlock(struct sx *sx, const char *file, int line);
int _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, int _sx_xlock_hard(struct sx *sx, uintptr_t v, uintptr_t tid, int opts,
const char *file, int line); const char *file, int line);
int _sx_slock_hard(struct sx *sx, int opts, const char *file, int line); int _sx_slock_hard(struct sx *sx, int opts, const char *file, int line);
void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int
@ -153,11 +153,12 @@ __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file,
int line) int line)
{ {
uintptr_t tid = (uintptr_t)td; uintptr_t tid = (uintptr_t)td;
uintptr_t v;
int error = 0; int error = 0;
if (sx->sx_lock != SX_LOCK_UNLOCKED || v = SX_LOCK_UNLOCKED;
!atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid)) if (!atomic_fcmpset_acq_ptr(&sx->sx_lock, &v, tid))
error = _sx_xlock_hard(sx, tid, opts, file, line); error = _sx_xlock_hard(sx, v, tid, opts, file, line);
else else
LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx, LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx,
0, 0, file, line, LOCKSTAT_WRITER); 0, 0, file, line, LOCKSTAT_WRITER);
@ -174,8 +175,7 @@ __sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line)
if (sx->sx_recurse == 0) if (sx->sx_recurse == 0)
LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx,
LOCKSTAT_WRITER); LOCKSTAT_WRITER);
if (sx->sx_lock != tid || if (!atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))
!atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))
_sx_xunlock_hard(sx, tid, file, line); _sx_xunlock_hard(sx, tid, file, line);
} }