fat_rwlock_tryrdlock() used to call fat_rwlock_get_slot__() which could block
in the "slow path" case. This commit adds fat_rwlock_try_get_slot__() which
does not block, even in the "slow path" case.
Signed-off-by: Daniele Di Proietto <ddiproie...@vmware.com>
---
lib/fat-rwlock.c | 33 ++++++++++++++++++++++++++++++++-
1 file changed, 32 insertions(+), 1 deletion(-)
diff --git a/lib/fat-rwlock.c b/lib/fat-rwlock.c
index 82dfbfe..be53b56 100644
--- a/lib/fat-rwlock.c
+++ b/lib/fat-rwlock.c
@@ -162,6 +162,33 @@ fat_rwlock_rdlock(const struct fat_rwlock *rwlock_)
}
}
+static struct fat_rwlock_slot *
+fat_rwlock_try_get_slot__(struct fat_rwlock *rwlock)
+{
+ struct fat_rwlock_slot *slot;
+
+ /* Fast path. */
+ slot = ovsthread_getspecific(rwlock->key);
+ if (slot) {
+ return slot;
+ }
+
+ /* Slow path: create a new slot for 'rwlock' in this thread. */
+
+ if (!ovs_mutex_trylock(&rwlock->mutex)) {
+ slot = xmalloc_cacheline(sizeof *slot);
+ slot->rwlock = rwlock;
+ ovs_mutex_init(&slot->mutex);
+ slot->depth = 0;
+
+ list_push_back(&rwlock->threads, &slot->list_node);
+ ovs_mutex_unlock(&rwlock->mutex);
+ ovsthread_setspecific(rwlock->key, slot);
+ }
+
+ return slot;
+}
+
/* Tries to lock 'rwlock' for reading. If successful, returns 0. If taking
* the lock would require blocking, returns EBUSY (without blocking). */
int
@@ -170,9 +197,13 @@ fat_rwlock_tryrdlock(const struct fat_rwlock *rwlock_)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
struct fat_rwlock *rwlock = CONST_CAST(struct fat_rwlock *, rwlock_);
- struct fat_rwlock_slot *this = fat_rwlock_get_slot__(rwlock);
+ struct fat_rwlock_slot *this = fat_rwlock_try_get_slot__(rwlock);
int error;
+ if (!this) {
+ return EBUSY;
+ }
+
switch (this->depth) {
case UINT_MAX:
return EBUSY;
--
2.1.0.rc1
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