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 use one write/modify instruction explicitly instead. This bug will not occur on idle workers, because they have another WORKER_NOT_RUNNING flags. Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com> --- kernel/workqueue.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 85bd340..050b2a5 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1739,10 +1739,13 @@ retry: for_each_busy_worker(worker, i, pos, gcwq) { struct work_struct *rebind_work = &worker->rebind_work; struct workqueue_struct *wq; + unsigned long worker_flags = worker->flags; /* morph UNBOUND to REBIND */ - worker->flags &= ~WORKER_UNBOUND; - worker->flags |= WORKER_REBIND; + worker_flags &= ~WORKER_UNBOUND; + worker_flags |= WORKER_REBIND; + /* ensure the wq_worker_sleeping() see the right flags */ + ACCESS_ONCE(worker->flags) = worker_flags; if (test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(rebind_work))) -- 1.7.4.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/