Date: Fri, 29 May 2009 13:56:34 +0000 (UTC) From: John Baldwin <jhb@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r193035 - head/sys/kern Message-ID: <200905291356.n4TDuYaP076613@svn.freebsd.org>
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Author: jhb Date: Fri May 29 13:56:34 2009 New Revision: 193035 URL: http://svn.freebsd.org/changeset/base/193035 Log: Tweak a few comments on adaptive spinning. Modified: head/sys/kern/kern_mutex.c head/sys/kern/kern_rwlock.c Modified: head/sys/kern/kern_mutex.c ============================================================================== --- head/sys/kern/kern_mutex.c Fri May 29 13:48:42 2009 (r193034) +++ head/sys/kern/kern_mutex.c Fri May 29 13:56:34 2009 (r193035) @@ -399,8 +399,11 @@ _mtx_lock_sleep(struct mtx *m, uintptr_t #ifdef ADAPTIVE_MUTEXES /* - * If the current owner of the lock is executing on another - * CPU quit the hard path and try to spin. + * The current lock owner might have started executing + * on another CPU (or the lock could have changed + * owners) while we were waiting on the turnstile + * chain lock. If so, drop the turnstile lock and try + * again. */ owner = (struct thread *)(v & ~MTX_FLAGMASK); if (TD_IS_RUNNING(owner)) { Modified: head/sys/kern/kern_rwlock.c ============================================================================== --- head/sys/kern/kern_rwlock.c Fri May 29 13:48:42 2009 (r193034) +++ head/sys/kern/kern_rwlock.c Fri May 29 13:56:34 2009 (r193035) @@ -412,8 +412,11 @@ _rw_rlock(struct rwlock *rw, const char #ifdef ADAPTIVE_RWLOCKS /* - * If the current owner of the lock is executing on another - * CPU quit the hard path and try to spin. + * The current lock owner might have started executing + * on another CPU (or the lock could have changed + * owners) while we were waiting on the turnstile + * chain lock. If so, drop the turnstile lock and try + * again. */ if ((v & RW_LOCK_READ) == 0) { owner = (struct thread *)RW_OWNER(v); @@ -714,8 +717,11 @@ _rw_wlock_hard(struct rwlock *rw, uintpt #ifdef ADAPTIVE_RWLOCKS /* - * If the current owner of the lock is executing on another - * CPU quit the hard path and try to spin. + * The current lock owner might have started executing + * on another CPU (or the lock could have changed + * owners) while we were waiting on the turnstile + * chain lock. If so, drop the turnstile lock and try + * again. */ if (!(v & RW_LOCK_READ)) { owner = (struct thread *)RW_OWNER(v);
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