Author: mjg
Date: Sun Feb 5 04:54:20 2017
New Revision: 313271
URL: https://svnweb.freebsd.org/changeset/base/313271
Log:
sx: switch to fcmpset
Discussed with: jhb
Tested by: pho (previous version)
Modified:
head/sys/kern/kern_sx.c
head/sys/sys/sx.h
Modified: head/sys/kern/kern_sx.c
==============================================================================
--- head/sys/kern/kern_sx.c Sun Feb 5 04:53:13 2017 (r313270)
+++ head/sys/kern/kern_sx.c Sun Feb 5 04:54:20 2017 (r313271)
@@ -530,15 +530,14 @@ sx_downgrade_(struct sx *sx, const char
* accessible from at least sx.h.
*/
int
-_sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file,
- int line)
+_sx_xlock_hard(struct sx *sx, uintptr_t x, uintptr_t tid, int opts,
+ const char *file, int line)
{
GIANT_DECLARE;
#ifdef ADAPTIVE_SX
volatile struct thread *owner;
u_int i, spintries = 0;
#endif
- uintptr_t x;
#ifdef LOCK_PROFILING
uint64_t waittime = 0;
int contested = 0;
@@ -563,8 +562,6 @@ _sx_xlock_hard(struct sx *sx, uintptr_t
lock_delay_arg_init(&lda, NULL);
#endif
- x = SX_READ_VALUE(sx);
-
/* If we already hold an exclusive lock, then recurse. */
if (__predict_false(lv_sx_owner(x) == (struct thread *)tid)) {
KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0,
@@ -587,9 +584,8 @@ _sx_xlock_hard(struct sx *sx, uintptr_t
#endif
for (;;) {
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;
- x = SX_READ_VALUE(sx);
continue;
}
#ifdef KDTRACE_HOOKS
@@ -902,7 +898,7 @@ _sx_slock_hard(struct sx *sx, int opts,
*/
if (x & SX_LOCK_SHARED) {
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)) {
if (LOCK_LOG_TEST(&sx->lock_object, 0))
CTR4(KTR_LOCK,
@@ -911,7 +907,6 @@ _sx_slock_hard(struct sx *sx, int opts,
(void *)(x + SX_ONE_SHARER));
break;
}
- x = SX_READ_VALUE(sx);
continue;
}
#ifdef KDTRACE_HOOKS
@@ -1085,7 +1080,7 @@ _sx_sunlock_hard(struct sx *sx, const ch
* so, just drop one and return.
*/
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)) {
if (LOCK_LOG_TEST(&sx->lock_object, 0))
CTR4(KTR_LOCK,
@@ -1094,8 +1089,6 @@ _sx_sunlock_hard(struct sx *sx, const ch
(void *)(x - SX_ONE_SHARER));
break;
}
-
- x = SX_READ_VALUE(sx);
continue;
}
@@ -1105,14 +1098,14 @@ _sx_sunlock_hard(struct sx *sx, const ch
*/
if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) {
MPASS(x == SX_SHARERS_LOCK(1));
- if (atomic_cmpset_rel_ptr(&sx->sx_lock,
- SX_SHARERS_LOCK(1), SX_LOCK_UNLOCKED)) {
+ x = SX_SHARERS_LOCK(1);
+ if (atomic_fcmpset_rel_ptr(&sx->sx_lock,
+ &x, SX_LOCK_UNLOCKED)) {
if (LOCK_LOG_TEST(&sx->lock_object, 0))
CTR2(KTR_LOCK, "%s: %p last succeeded",
__func__, sx);
break;
}
- x = SX_READ_VALUE(sx);
continue;
}
Modified: head/sys/sys/sx.h
==============================================================================
--- head/sys/sys/sx.h Sun Feb 5 04:53:13 2017 (r313270)
+++ head/sys/sys/sx.h Sun Feb 5 04:54:20 2017 (r313271)
@@ -109,7 +109,7 @@ int _sx_slock(struct sx *sx, int opts, c
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_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);
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
@@ -153,11 +153,12 @@ __sx_xlock(struct sx *sx, struct thread
int line)
{
uintptr_t tid = (uintptr_t)td;
+ uintptr_t v;
int error = 0;
- if (sx->sx_lock != SX_LOCK_UNLOCKED ||
- !atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid))
- error = _sx_xlock_hard(sx, tid, opts, file, line);
+ v = SX_LOCK_UNLOCKED;
+ if (!atomic_fcmpset_acq_ptr(&sx->sx_lock, &v, tid))
+ error = _sx_xlock_hard(sx, v, tid, opts, file, line);
else
LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx,
0, 0, file, line, LOCKSTAT_WRITER);
@@ -174,8 +175,7 @@ __sx_xunlock(struct sx *sx, struct threa
if (sx->sx_recurse == 0)
LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx,
LOCKSTAT_WRITER);
- if (sx->sx_lock != tid ||
- !atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))
+ if (!atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))
_sx_xunlock_hard(sx, tid, file, line);
}
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