cvs commit: src/sys/kern kern_mutex.c kern_rwlock.c
attilio at FreeBSD.org
Mon Nov 26 14:37:35 PST 2007
attilio 2007-11-26 22:37:35 UTC
FreeBSD src repository
sys/kern kern_mutex.c kern_rwlock.c
Simplify the adaptive spinning algorithm in rwlock and mutex:
currently, before to spin the turnstile spinlock is acquired and the
waiters flag is set.
This is not strictly necessary, so just spin before to acquire the
spinlock and to set the flags.
This will simplify a lot other functions too, as now we have the waiters
flag set only if there are actually waiters.
This should make wakeup/sleeping couplet faster under intensive mutex
This also fixes a bug in rw_try_upgrade() in the adaptive case, where
turnstile_lookup() will recurse on the ts_lock lock that will never be
really released .
 Reported by: jeff with Nokia help
Tested by: pho, kris (earlier, bugged version of rwlock part)
Discussed with: jhb , jeff
MFC after: 1 week
 John had a similar patch about 6.x and/or 7.x about mutexes probabilly
Revision Changes Path
1.201 +41 -29 src/sys/kern/kern_mutex.c
1.32 +72 -112 src/sys/kern/kern_rwlock.c
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