Date: Fri, 12 Jan 2018 13:40:50 +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: r327875 - head/sys/kern Message-ID: <201801121340.w0CDeoI9046644@repo.freebsd.org>
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Author: mjg Date: Fri Jan 12 13:40:50 2018 New Revision: 327875 URL: https://svnweb.freebsd.org/changeset/base/327875 Log: mtx: use fcmpset to cover setting MTX_CONTESTED Modified: head/sys/kern/kern_mutex.c Modified: head/sys/kern/kern_mutex.c ============================================================================== --- head/sys/kern/kern_mutex.c Fri Jan 12 13:39:02 2018 (r327874) +++ head/sys/kern/kern_mutex.c Fri Jan 12 13:40:50 2018 (r327875) @@ -578,6 +578,7 @@ __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v) ts = turnstile_trywait(&m->lock_object); v = MTX_READ_VALUE(m); +retry_turnstile: /* * Check if the lock has been released while spinning for @@ -609,10 +610,8 @@ __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v) * or the state of the MTX_RECURSED bit changed. */ if ((v & MTX_CONTESTED) == 0 && - !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) { - turnstile_cancel(ts); - v = MTX_READ_VALUE(m); - continue; + !atomic_fcmpset_ptr(&m->mtx_lock, &v, v | MTX_CONTESTED)) { + goto retry_turnstile; } /*
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