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From: Mark Johnston <markj@FreeBSD.org>
Date: Sat, 27 Jul 2019 16:11:04 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r350373 - in stable/12/sys: kern sys
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Author: markj
Date: Sat Jul 27 16:11:04 2019
New Revision: 350373
URL: https://svnweb.freebsd.org/changeset/base/350373
Log:
MFC r350310:
Fix the turnstile_lock() KPI.
Modified:
stable/12/sys/kern/subr_epoch.c
stable/12/sys/kern/subr_turnstile.c
stable/12/sys/sys/turnstile.h
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sys/kern/subr_epoch.c
==============================================================================
--- stable/12/sys/kern/subr_epoch.c Sat Jul 27 15:04:10 2019 (r350372)
+++ stable/12/sys/kern/subr_epoch.c Sat Jul 27 16:11:04 2019 (r350373)
@@ -440,26 +440,20 @@ epoch_block_handler_preempt(struct ck_epoch *global __
*/
critical_enter();
thread_unlock(td);
- owner = turnstile_lock(ts, &lock);
- /*
- * The owner pointer indicates that the lock succeeded.
- * Only in case we hold the lock and the turnstile we
- * locked is still the one that curwaittd is blocked on
- * can we continue. Otherwise the turnstile pointer has
- * been changed out from underneath us, as in the case
- * where the lock holder has signalled curwaittd,
- * and we need to continue.
- */
- if (owner != NULL && ts == curwaittd->td_blocked) {
- MPASS(TD_IS_INHIBITED(curwaittd) &&
- TD_ON_LOCK(curwaittd));
- critical_exit();
- turnstile_wait(ts, owner, curwaittd->td_tsqueue);
- counter_u64_add(turnstile_count, 1);
- thread_lock(td);
- return;
- } else if (owner != NULL)
+
+ if (turnstile_lock(ts, &lock, &owner)) {
+ if (ts == curwaittd->td_blocked) {
+ MPASS(TD_IS_INHIBITED(curwaittd) &&
+ TD_ON_LOCK(curwaittd));
+ critical_exit();
+ turnstile_wait(ts, owner,
+ curwaittd->td_tsqueue);
+ counter_u64_add(turnstile_count, 1);
+ thread_lock(td);
+ return;
+ }
turnstile_unlock(ts, lock);
+ }
thread_lock(td);
critical_exit();
KASSERT(td->td_locks == locksheld,
Modified: stable/12/sys/kern/subr_turnstile.c
==============================================================================
--- stable/12/sys/kern/subr_turnstile.c Sat Jul 27 15:04:10 2019 (r350372)
+++ stable/12/sys/kern/subr_turnstile.c Sat Jul 27 16:11:04 2019 (r350373)
@@ -566,24 +566,26 @@ turnstile_trywait(struct lock_object *lock)
return (ts);
}
-struct thread *
-turnstile_lock(struct turnstile *ts, struct lock_object **lockp)
+bool
+turnstile_lock(struct turnstile *ts, struct lock_object **lockp,
+ struct thread **tdp)
{
struct turnstile_chain *tc;
struct lock_object *lock;
if ((lock = ts->ts_lockobj) == NULL)
- return (NULL);
+ return (false);
tc = TC_LOOKUP(lock);
mtx_lock_spin(&tc->tc_lock);
mtx_lock_spin(&ts->ts_lock);
if (__predict_false(lock != ts->ts_lockobj)) {
mtx_unlock_spin(&tc->tc_lock);
mtx_unlock_spin(&ts->ts_lock);
- return (NULL);
+ return (false);
}
*lockp = lock;
- return (ts->ts_owner);
+ *tdp = ts->ts_owner;
+ return (true);
}
void
Modified: stable/12/sys/sys/turnstile.h
==============================================================================
--- stable/12/sys/sys/turnstile.h Sat Jul 27 15:04:10 2019 (r350372)
+++ stable/12/sys/sys/turnstile.h Sat Jul 27 16:11:04 2019 (r350373)
@@ -100,7 +100,8 @@ int turnstile_signal(struct turnstile *, int);
struct turnstile *turnstile_trywait(struct lock_object *);
void turnstile_unpend(struct turnstile *);
void turnstile_wait(struct turnstile *, struct thread *, int);
-struct thread *turnstile_lock(struct turnstile *, struct lock_object **);
+bool turnstile_lock(struct turnstile *, struct lock_object **,
+ struct thread **);
void turnstile_unlock(struct turnstile *, struct lock_object *);
void turnstile_assert(struct turnstile *);
#endif /* _KERNEL */