sched: Remove pointless preemption disable in sched_submit_work()

Neither wq_worker_sleeping() nor io_wq_worker_sleeping() require to be invoked
with preemption disabled:

  - The worker flag checks operations only need to be serialized against
    the worker thread itself.

  - The accounting and worker pool operations are serialized with locks.

which means that disabling preemption has neither a reason nor a
value. Remove it and update the stale comment.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lkml.kernel.org/r/8735pnafj7.ffs@tglx

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e33b03c2bb9a83cca553c97f05ad006826f2f87d..e47d7e55c46a7e102bd67ae9865adf556db2335d 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6251,20 +6251,14 @@ static inline void sched_submit_work(struct task_struct *tsk)
 
        task_flags = tsk->flags;
        /*
-        * If a worker went to sleep, notify and ask workqueue whether
-        * it wants to wake up a task to maintain concurrency.
-        * As this function is called inside the schedule() context,
-        * we disable preemption to avoid it calling schedule() again
-        * in the possible wakeup of a kworker and because wq_worker_sleeping()
-        * requires it.
+        * If a worker goes to sleep, notify and ask workqueue whether it
+        * wants to wake up a task to maintain concurrency.
         */
        if (task_flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
-               preempt_disable();
                if (task_flags & PF_WQ_WORKER)
                        wq_worker_sleeping(tsk);
                else
                        io_wq_worker_sleeping(tsk);
-               preempt_enable_no_resched();
        }
 
        if (tsk_is_pi_blocked(tsk))