Date: Fri, 4 Apr 2008 10:00:46 +0000 (UTC) From: Jeff Roberson <jeff@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/kern kern_rwlock.c Message-ID: <200804041000.m34A0kSL020625@repoman.freebsd.org>
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jeff 2008-04-04 10:00:46 UTC
FreeBSD src repository
Modified files:
sys/kern kern_rwlock.c
Log:
- Add sysctls at debug.rwlock to control the behavior of the speculative
spinning when readers hold a lock. This spinning is speculative because,
unlike the write case, we can not test whether the owners are running.
- Add speculative read spinning for readers who are blocked by pending
writers while a read lock is still held. This allows the thread to
spin until the write lock succeeds after which it may spin until the
writer has released the lock. This prevents excessive context switches
when readers and writers both hold the lock for brief periods.
Sponsored by: Nokia
Revision Changes Path
1.38 +26 -3 src/sys/kern/kern_rwlock.c
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