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[v1,1/2] linux-generic: rwlock: fix odp_rwlock_read_trylock()

Message ID 1493935208-7891-3-git-send-email-odpbot@yandex.ru
State New
Headers show
Series [v1,1/2] linux-generic: rwlock: fix odp_rwlock_read_trylock() | expand

Commit Message

Github ODP bot May 4, 2017, 10 p.m. UTC 
From: Dmitry Eremin-Solenikov <dmitry.ereminsolenikov@linaro.org>


odp_rwlock_read_trylock() currently works only if there are no readers
(and writers) as it compares counter with 0. Make it actually work in
case there are other active readers.

Fixes: https://bugs.linaro.org/show_bug.cgi?id=2974

Signed-off-by: Dmitry Eremin-Solenikov <dmitry.ereminsolenikov@linaro.org>

---
/** Email created from pull request 19 (lumag:fix-rwlock)
 ** https://github.com/Linaro/odp/pull/19
 ** Patch: https://github.com/Linaro/odp/pull/19.patch
 ** Base sha: 79ba737a404d2833ad33d8f84ed6ce82c9a8c18e
 ** Merge commit sha: 8448157882fac03287253bf54c19284b6d52246e
 **/
 platform/linux-generic/odp_rwlock.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
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Patch

diff --git a/platform/linux-generic/odp_rwlock.c b/platform/linux-generic/odp_rwlock.c
index 13c17a2..5bef13a 100644
--- a/platform/linux-generic/odp_rwlock.c
+++ b/platform/linux-generic/odp_rwlock.c
@@ -33,9 +33,14 @@  void odp_rwlock_read_lock(odp_rwlock_t *rwlock)
 
 int odp_rwlock_read_trylock(odp_rwlock_t *rwlock)
 {
-	uint32_t zero = 0;
+	uint32_t cnt = odp_atomic_load_u32(&rwlock->cnt);
+
+	while (cnt != (uint32_t)-1) {
+		if (odp_atomic_cas_acq_u32(&rwlock->cnt, &cnt, cnt + 1))
+			return 1;
+	}
 
-	return odp_atomic_cas_acq_u32(&rwlock->cnt, &zero, (uint32_t)1);
+	return 0;
 }
 
 void odp_rwlock_read_unlock(odp_rwlock_t *rwlock)