diff options
| -rw-r--r-- | thread-pool.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/thread-pool.c b/thread-pool.c index 80749b77e0..651b32419b 100644 --- a/thread-pool.c +++ b/thread-pool.c @@ -39,6 +39,11 @@ struct ThreadPoolElement { BlockDriverAIOCB common; ThreadPoolFunc *func; void *arg; + + /* Moving state out of THREAD_QUEUED is protected by lock. After + * that, only the worker thread can write to it. Reads and writes + * of state and ret are ordered with memory barriers. + */ enum ThreadState state; int ret; @@ -95,9 +100,12 @@ static void *worker_thread(void *unused) ret = req->func(req->arg); - qemu_mutex_lock(&lock); - req->state = THREAD_DONE; req->ret = ret; + /* Write ret before state. */ + smp_wmb(); + req->state = THREAD_DONE; + + qemu_mutex_lock(&lock); if (pending_cancellations) { qemu_cond_broadcast(&check_cancel); } @@ -162,11 +170,10 @@ restart: trace_thread_pool_complete(elem, elem->common.opaque, elem->ret); } if (elem->state == THREAD_DONE && elem->common.cb) { - qemu_mutex_lock(&lock); - int ret = elem->ret; - qemu_mutex_unlock(&lock); QLIST_REMOVE(elem, all); - elem->common.cb(elem->common.opaque, ret); + /* Read state before ret. */ + smp_rmb(); + elem->common.cb(elem->common.opaque, elem->ret); qemu_aio_release(elem); goto restart; } else { |