Messages in this thread Patch in this message | | | From | Lai Jiangshan <> | Subject | [PATCH 2/3 V2] workqueue: ensure the wq_worker_sleeping() see the right flags | Date | Tue, 28 Aug 2012 19:34:38 +0800 |
| |
The compiler may compile this code into TWO write/modify instructions. worker->flags &= ~WORKER_UNBOUND; worker->flags |= WORKER_REBIND;
so the other CPU may see the temporary of worker->flags which has not WORKER_UNBOUND nor WORKER_REBIND, it will wrongly do local wake up.
So we simply change the code that WORKER_UNBOUND is cleared in busy_worker_rebind_fn(), not in rebind_workers(). And REBIND is not used for busy_worker, busy_worker_rebind_fn() knows itself need to do rebind when it is called.
Because the rebind_workers() will wait busy_worker_rebind_fn() to finish rebinding and clearing, the CPU can't be offline, busy_worker_rebind_fn() will not clear the wrong WORKER_UNBOUND.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> --- kernel/workqueue.c | 6 +----- 1 files changed, 1 insertions(+), 5 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 5f63883..3e0bd20 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1354,7 +1354,7 @@ static void busy_worker_rebind_fn(struct work_struct *work) /* CPU must be online at this point */ WARN_ON(!worker_maybe_bind_and_lock(worker)); - worker_clr_flags(worker, WORKER_REBIND); + worker_clr_flags(worker, WORKER_UNBOUND); spin_unlock_irq(&gcwq->lock); /* all_cnt is only accessed by the bound CPU, don't need any lock */ @@ -1420,10 +1420,6 @@ static void rebind_workers(struct global_cwq *gcwq) for_each_busy_worker(worker, i, pos, gcwq) { struct work_struct *rebind_work = &worker->rebind_work; - /* morph UNBOUND to REBIND */ - worker->flags &= ~WORKER_UNBOUND; - worker->flags |= WORKER_REBIND; - if (test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(rebind_work))) continue; -- 1.7.4.4
| |