From cdcee493a206829c1a3ccc94df157c9720285eb7 Mon Sep 17 00:00:00 2001 From: jhb Date: Fri, 29 May 2009 13:56:34 +0000 Subject: Tweak a few comments on adaptive spinning. --- sys/kern/kern_mutex.c | 7 +++++-- sys/kern/kern_rwlock.c | 14 ++++++++++---- 2 files changed, 15 insertions(+), 6 deletions(-) diff --git a/sys/kern/kern_mutex.c b/sys/kern/kern_mutex.c index 49f9c59..17c72eb 100644 --- a/sys/kern/kern_mutex.c +++ b/sys/kern/kern_mutex.c @@ -399,8 +399,11 @@ _mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file, #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)) { diff --git a/sys/kern/kern_rwlock.c b/sys/kern/kern_rwlock.c index 993acfa..cc5f4f132 100644 --- a/sys/kern/kern_rwlock.c +++ b/sys/kern/kern_rwlock.c @@ -412,8 +412,11 @@ _rw_rlock(struct rwlock *rw, const char *file, int line) #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, uintptr_t tid, const char *file, int line) #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); -- cgit v1.1