From 95b147967216a057d51a1b970da777486be716e3 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 28 Sep 2011 18:00:02 -0400 Subject: [PATCH] next step making barrier self-sync'd destruction safe i think this works, but it can be simplified. (next step) --- src/thread/pthread_barrier_destroy.c | 8 ++++++-- src/thread/pthread_barrier_wait.c | 16 ++++++++++++---- 2 files changed, 18 insertions(+), 6 deletions(-) diff --git a/src/thread/pthread_barrier_destroy.c b/src/thread/pthread_barrier_destroy.c index 3ebc2b39..e0da197a 100644 --- a/src/thread/pthread_barrier_destroy.c +++ b/src/thread/pthread_barrier_destroy.c @@ -5,8 +5,12 @@ void __vm_lock(int), __vm_unlock(void); int pthread_barrier_destroy(pthread_barrier_t *b) { if (b->_b_limit < 0) { - int seq = b->_b_seq; - if (seq & 1) __wait(&b->_b_seq, 0, seq, 0); + if (b->_b_lock) { + int v; + a_or(&b->_b_lock, INT_MIN); + while ((v = b->_b_lock) & INT_MAX) + __wait(&b->_b_lock, 0, v, 0); + } __vm_lock(-1); __vm_unlock(); } diff --git a/src/thread/pthread_barrier_wait.c b/src/thread/pthread_barrier_wait.c index a97f6d56..9b1edbf9 100644 --- a/src/thread/pthread_barrier_wait.c +++ b/src/thread/pthread_barrier_wait.c @@ -23,11 +23,12 @@ static int pshared_barrier_wait(pthread_barrier_t *b) int limit = (b->_b_limit & INT_MAX) + 1; int seq; int ret = 0; + int v, w; if (limit==1) return PTHREAD_BARRIER_SERIAL_THREAD; - while (a_swap(&b->_b_lock, 1)) - __wait(&b->_b_lock, &b->_b_waiters, 1, 0); + while ((v=a_cas(&b->_b_lock, 0, limit))) + __wait(&b->_b_lock, &b->_b_waiters, v, 0); seq = b->_b_seq; @@ -46,12 +47,19 @@ static int pshared_barrier_wait(pthread_barrier_t *b) if (a_fetch_add(&b->_b_count, -1)==1) { b->_b_seq++; __wake(&b->_b_seq, -1, 0); - a_store(&b->_b_lock, 0); - if (b->_b_waiters) __wake(&b->_b_lock, 1, 0); } else { __wait(&b->_b_seq, 0, seq+1, 0); } + /* Perform a recursive unlock suitable for self-sync'd destruction */ + do { + v = b->_b_lock; + w = b->_b_waiters; + } while (a_cas(&b->_b_lock, v, v-1 & INT_MAX) != v); + + if (v==INT_MIN+1 || (v==1 && w)) + __wake(&b->_b_lock, 1, 0); + __vm_unlock(); return ret; -- 2.20.1