Date: Sat, 13 Jan 2018 00:05:31 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r327905 - head/sys/kern Message-ID: <201801130005.w0D05Vhk016568@repo.freebsd.org>
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Author: mjg Date: Sat Jan 13 00:05:31 2018 New Revision: 327905 URL: https://svnweb.freebsd.org/changeset/base/327905 Log: rwlock: try regular read unlock even in the hard path Saves on turnstile trips if the lock got more readers. Modified: head/sys/kern/kern_rwlock.c Modified: head/sys/kern/kern_rwlock.c ============================================================================== --- head/sys/kern/kern_rwlock.c Sat Jan 13 00:04:11 2018 (r327904) +++ head/sys/kern/kern_rwlock.c Sat Jan 13 00:05:31 2018 (r327905) @@ -771,9 +771,9 @@ __rw_runlock_hard(struct rwlock *rw, struct thread *td turnstile_chain_lock(&rw->lock_object); v = RW_READ_VALUE(rw); retry_ts: - if (__predict_false(RW_READERS(v) > 1)) { + if (__rw_runlock_try(rw, td, &v)) { turnstile_chain_unlock(&rw->lock_object); - continue; + break; } v &= (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER);
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