[sr-dev] git:master:47aa94c6: core/futex: fix bug in futex_try

[tsearle]

Module: kamailio
Branch: master
Commit: 47aa94c694e5471fa85bb15c372f9120876e4927
URL: https://github.com/kamailio/kamailio/commit/47aa94c694e5471fa85bb15c372f9120876e4927

Author: tsearle <tsearle at gmail.com>
Committer: tsearle <tsearle at gmail.com>
Date: 2016-02-25T09:56:09+01:00

core/futex: fix bug in futex_try

atomic_cmpxchg returns the previous value.  If the previous value was 0 then it was previously unlocked and we now have acquired the lock.

Thus, it should  be c==0 that is considered as the case we enter the lock, not c!=0

As far as I can tell, lock_try (and lock_set_try) are currently no used anywhere in the code, so this fix shoudn't have any impact

---

Modified: futexlock.h

---

Diff:  https://github.com/kamailio/kamailio/commit/47aa94c694e5471fa85bb15c372f9120876e4927.diff
Patch: https://github.com/kamailio/kamailio/commit/47aa94c694e5471fa85bb15c372f9120876e4927.patch

---

diff --git a/futexlock.h b/futexlock.h
index 7aa7c73..db2fca4 100644
--- a/futexlock.h
+++ b/futexlock.h
@@ -142,7 +142,7 @@ static inline int futex_try(futex_lock_t* lock)
 {
 	int c;
 	c=atomic_cmpxchg(lock, 0, 1);
-	if (likely(c))
+	if (likely(c==0))
 		membar_enter_lock();
 	return c;
 }