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author | Ben Pfaff <blp@nicira.com> | 2014-02-21 10:53:49 -0800 |
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committer | Ben Pfaff <blp@nicira.com> | 2014-02-21 16:27:10 -0800 |
commit | 6b59b543c840ac82acc4d57f865c0b5e331ac590 (patch) | |
tree | 6da0af0a46ab13351c99257981ac5103f650b553 /lib/ovs-thread.c | |
parent | 5a0702383b61d329f0640b5b4da4869a4b4f1384 (diff) | |
download | openvswitch-6b59b543c840ac82acc4d57f865c0b5e331ac590.tar.gz |
ovs-thread: Use fair (but nonrecursive) rwlocks on glibc.
glibc supports two kinds of rwlocks:
- The default kind of rwlock always allows recursive read-locks to
succeed, but threads blocked on acquiring the write-lock are treated
unfairly, causing them to be delayed indefinitely as long as new
readers continue to come along.
- An alternative "writer nonrecursive" rwlock allows recursive
read-locks to succeed only if there are no threads waiting for the
write-lock. Otherwise, recursive read-lock attempts deadlock in
the presence of blocking write-lock attempts. However, this kind
of rwlock is fair to writer.
POSIX allows the latter behavior, which essentially means that any portable
pthread program cannot try to take read-locks recursively. Since that's
true, we might as well use the latter kind of rwlock with glibc and get the
benefit of fairness of writers.
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Joe Stringer <joestringer@nicira.com>
Diffstat (limited to 'lib/ovs-thread.c')
-rw-r--r-- | lib/ovs-thread.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/lib/ovs-thread.c b/lib/ovs-thread.c index f0b1e9e81..4dfccaf3e 100644 --- a/lib/ovs-thread.c +++ b/lib/ovs-thread.c @@ -125,6 +125,12 @@ XPTHREAD_FUNC1(pthread_mutexattr_destroy, pthread_mutexattr_t *); XPTHREAD_FUNC2(pthread_mutexattr_settype, pthread_mutexattr_t *, int); XPTHREAD_FUNC2(pthread_mutexattr_gettype, pthread_mutexattr_t *, int *); +XPTHREAD_FUNC1(pthread_rwlockattr_init, pthread_rwlockattr_t *); +XPTHREAD_FUNC1(pthread_rwlockattr_destroy, pthread_rwlockattr_t *); +#ifdef PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP +XPTHREAD_FUNC2(pthread_rwlockattr_setkind_np, pthread_rwlockattr_t *, int); +#endif + XPTHREAD_FUNC2(pthread_cond_init, pthread_cond_t *, pthread_condattr_t *); XPTHREAD_FUNC1(pthread_cond_destroy, pthread_cond_t *); XPTHREAD_FUNC1(pthread_cond_signal, pthread_cond_t *); @@ -183,13 +189,21 @@ void ovs_rwlock_init(const struct ovs_rwlock *l_) { struct ovs_rwlock *l = CONST_CAST(struct ovs_rwlock *, l_); + pthread_rwlockattr_t attr; int error; l->where = NULL; + + xpthread_rwlockattr_init(&attr); +#ifdef PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP + xpthread_rwlockattr_setkind_np( + &attr, PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP); +#endif error = pthread_rwlock_init(&l->lock, NULL); if (OVS_UNLIKELY(error)) { ovs_abort(error, "pthread_rwlock_init failed"); } + xpthread_rwlockattr_destroy(&attr); } void |