[RFC,65/86] treewide: task_work: remove cond_resched()

Commit Message

Ankur Arora Nov. 7, 2023, 11:08 p.m. UTC

The cond_resched() call was added in commit f341861fb0b7 ("task_work:
add a scheduling point in task_work_run()") because of softlockups
when processes with a large number of open sockets would exit.

Given the always-on PREEMPTION, we should be able to remove it
without much concern. However, task_work_run() does get called
from some "interesting" places: one of them being the
exit_to_user_loop() itself.

That means that if TIF_NEED_RESCHED (or TIF_NEED_RESCHED_LAZY) were
to be set once we were in a potentially long running task_work_run()
all, then we would ignore the need-resched flags and there would
be no call to schedule().

However, in that case, the next timer tick should cause rescheduling
in irqentry_exit_cond_resched(), since then the TIF_NEED_RESCHED flag
(even if the original flag were TIF_NEED_RESCHED_LAZY the tick would
upgrade that.)

Cc: Oleg Nesterov <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Signed-off-by: Ankur Arora <[e-mail]>
---
 kernel/task_work.c | 1 -
 1 file changed, 1 deletion(-)

Patch

diff --git a/kernel/task_work.c b/kernel/task_work.c
index 95a7e1b7f1da..6a891465c8e1 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -179,7 +179,6 @@  void task_work_run(void)
 			next = work->next;
 			work->func(work);
 			work = next;
-			cond_resched();
 		} while (work);
 	}
 }