From de543b05c87d79a9313991810e9ee8ecdaad8f19 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 28 Sep 2011 19:45:37 -0400 Subject: [PATCH] fix excessive/insufficient wakes in __vm_unlock there is no need to send a wake when the lock count does not hit zero, but when it does, all waiters must be woken (since all with the same sign are eligible to obtain the lock). --- src/thread/pthread_barrier_wait.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/src/thread/pthread_barrier_wait.c b/src/thread/pthread_barrier_wait.c index 71f7b5fe..6052925a 100644 --- a/src/thread/pthread_barrier_wait.c +++ b/src/thread/pthread_barrier_wait.c @@ -13,9 +13,9 @@ void __vm_lock(int inc) void __vm_unlock(void) { - if (vmlock[0]>0) a_dec(vmlock); - else a_inc(vmlock); - if (vmlock[1]) __wake(vmlock, 1, 1); + int inc = vmlock[0]>0 ? -1 : 1; + if (a_fetch_add(vmlock, inc)==-inc && vmlock[1]) + __wake(vmlock, -1, 1); } static int pshared_barrier_wait(pthread_barrier_t *b) -- GitLab