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rwlock: stop re-reading the owner when going to sleep

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This commit is contained in:
mjg 2017-11-25 20:08:11 +00:00
parent 9014a6e40c
commit d5c5e62cc7
1 changed files with 11 additions and 8 deletions
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19
sys/kern/kern_rwlock.c
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@ -411,8 +411,8 @@ __rw_rlock_hard(struct rwlock *rw, struct thread *td, uintptr_t v
LOCK_FILE_LINE_ARG_DEF)
{
struct turnstile *ts;
struct thread *owner;
#ifdef ADAPTIVE_RWLOCKS
volatile struct thread *owner;
int spintries = 0;
int i, n;
#endif
@ -531,6 +531,8 @@ __rw_rlock_hard(struct rwlock *rw, struct thread *td, uintptr_t v
continue;
}
owner = lv_rw_wowner(v);
#ifdef ADAPTIVE_RWLOCKS
/*
* The current lock owner might have started executing
@ -539,8 +541,7 @@ __rw_rlock_hard(struct rwlock *rw, struct thread *td, uintptr_t v
* chain lock. If so, drop the turnstile lock and try
* again.
*/
if ((v & RW_LOCK_READ) == 0) {
owner = (struct thread *)RW_OWNER(v);
if (owner != NULL) {
if (TD_IS_RUNNING(owner)) {
turnstile_cancel(ts);
continue;
@ -581,7 +582,8 @@ __rw_rlock_hard(struct rwlock *rw, struct thread *td, uintptr_t v
#ifdef KDTRACE_HOOKS
sleep_time -= lockstat_nsecs(&rw->lock_object);
#endif
turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE);
MPASS(owner == rw_owner(rw));
turnstile_wait(ts, owner, TS_SHARED_QUEUE);
#ifdef KDTRACE_HOOKS
sleep_time += lockstat_nsecs(&rw->lock_object);
sleep_cnt++;
@ -850,8 +852,8 @@ __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v LOCK_FILE_LINE_ARG_DEF)
uintptr_t tid;
struct rwlock *rw;
struct turnstile *ts;
struct thread *owner;
#ifdef ADAPTIVE_RWLOCKS
volatile struct thread *owner;
int spintries = 0;
int i, n;
#endif
@ -981,6 +983,7 @@ __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v LOCK_FILE_LINE_ARG_DEF)
#endif
ts = turnstile_trywait(&rw->lock_object);
v = RW_READ_VALUE(rw);
owner = lv_rw_wowner(v);
#ifdef ADAPTIVE_RWLOCKS
/*
@ -990,8 +993,7 @@ __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v LOCK_FILE_LINE_ARG_DEF)
* chain lock. If so, drop the turnstile lock and try
* again.
*/
if (!(v & RW_LOCK_READ)) {
owner = (struct thread *)RW_OWNER(v);
if (owner != NULL) {
if (TD_IS_RUNNING(owner)) {
turnstile_cancel(ts);
continue;
@ -1045,7 +1047,8 @@ __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v LOCK_FILE_LINE_ARG_DEF)
#ifdef KDTRACE_HOOKS
sleep_time -= lockstat_nsecs(&rw->lock_object);
#endif
turnstile_wait(ts, rw_owner(rw), TS_EXCLUSIVE_QUEUE);
MPASS(owner == rw_owner(rw));
turnstile_wait(ts, owner, TS_EXCLUSIVE_QUEUE);
#ifdef KDTRACE_HOOKS
sleep_time += lockstat_nsecs(&rw->lock_object);
sleep_cnt++;