Date: Tue, 3 Jan 2017 23:08:11 +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: r311194 - head/sys/kern Message-ID: <201701032308.v03N8B4Q047670@repo.freebsd.org>
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Author: mjg Date: Tue Jan 3 23:08:11 2017 New Revision: 311194 URL: https://svnweb.freebsd.org/changeset/base/311194 Log: Reduce lock accesses in thread lock similarly to r311172. Modified: head/sys/kern/kern_mutex.c Modified: head/sys/kern/kern_mutex.c ============================================================================== --- head/sys/kern/kern_mutex.c Tue Jan 3 23:07:40 2017 (r311193) +++ head/sys/kern/kern_mutex.c Tue Jan 3 23:08:11 2017 (r311194) @@ -754,7 +754,7 @@ void thread_lock_flags_(struct thread *td, int opts, const char *file, int line) { struct mtx *m; - uintptr_t tid; + uintptr_t tid, v; struct lock_delay_arg lda; #ifdef LOCK_PROFILING int contested = 0; @@ -796,10 +796,15 @@ retry: m->lock_object.lo_name, file, line)); WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); + v = MTX_READ_VALUE(m); for (;;) { - if (m->mtx_lock == MTX_UNOWNED && _mtx_obtain_lock(m, tid)) - break; - if (m->mtx_lock == tid) { + if (v == MTX_UNOWNED) { + if (_mtx_obtain_lock(m, tid)) + break; + v = MTX_READ_VALUE(m); + continue; + } + if (v == tid) { m->mtx_recurse++; break; } @@ -810,7 +815,7 @@ retry: &contested, &waittime); /* Give interrupts a chance while we spin. */ spinlock_exit(); - while (m->mtx_lock != MTX_UNOWNED) { + do { if (lda.spin_cnt < 10000000) { lock_delay(&lda); } else { @@ -824,7 +829,8 @@ retry: } if (m != td->td_lock) goto retry; - } + v = MTX_READ_VALUE(m); + } while (v != MTX_UNOWNED); spinlock_enter(); } if (m == td->td_lock)
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