[PATCH] io_uring/io-wq: don't clear PF_IO_WORKER on exit

[Jens Axboe <axboe@kernel.dk>]

A recent commit gated the core dumping task exit logic on current->flags
remaining consistent in terms of PF_{IO,USER}_WORKER at task exit time.
This exposed a problem with the io-wq handling of that, which explicitly
clears PF_IO_WORKER before calling do_exit().

The reasons for this manual clear of PF_IO_WORKER is historical, where
io-wq used to potentially trigger a sleep on exit. As the io-wq thread
is exiting, it should not participate any further accounting. But these
days we don't need to rely on current->flags anymore, so we can safely
remove the PF_IO_WORKER clearing.

Reported-by: Zorro Lang <zlang@redhat.com>
Reported-by: Dave Chinner <david@fromorbit.com>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/all/ZIZSPyzReZkGBEFy@dread.disaster.area/
Fixes: f9010dbdce91 ("fork, vhost: Use CLONE_THREAD to fix freezer/ps regression")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

---

diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
index b2715988791e..fe38eb0cbc82 100644
--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -221,9 +221,6 @@ static void io_worker_exit(struct io_worker *worker)
 	raw_spin_unlock(&wq->lock);
 	io_wq_dec_running(worker);
 	worker->flags = 0;
-	preempt_disable();
-	current->flags &= ~PF_IO_WORKER;
-	preempt_enable();
 
 	kfree_rcu(worker, rcu);
 	io_worker_ref_put(wq);

-- 
Jens Axboe