Author: mjg
Date: Sat Nov 25 20:08:11 2017
New Revision: 326194
URL: https://svnweb.freebsd.org/changeset/base/326194
Log:
rwlock: stop re-reading the owner when going to sleep
Modified:
head/sys/kern/kern_rwlock.c
Modified: head/sys/kern/kern_rwlock.c
==============================================================================
--- head/sys/kern/kern_rwlock.c Sat Nov 25 17:12:48 2017 (r326193)
+++ head/sys/kern/kern_rwlock.c Sat Nov 25 20:08:11 2017 (r326194)
@@ -411,8 +411,8 @@ __rw_rlock_hard(struct rwlock *rw, struct thread *td,
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,
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,
* 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,
#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 LOC
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 LOC
#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 LOC
* 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 LOC
#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++;
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