linux-kernel - [PATCH 2/2] signal: don't allow STOP on PF_IO

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Date:   Sat, 20 Mar 2021 09:38:32 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     io-uring@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, ebiederm@...ssion.com,
        linux-kernel@...r.kernel.org, oleg@...hat.com,
        Jens Axboe <axboe@...nel.dk>,
        Stefan Metzmacher <metze@...ba.org>
Subject: [PATCH 2/2] signal: don't allow STOP on PF_IO_WORKER threads

Just like we don't allow normal signals to IO threads, don't deliver a
STOP to a task that has PF_IO_WORKER set. The IO threads don't take
signals in general, and have no means of flushing out a stop either.

Reported-by: Stefan Metzmacher <metze@...ba.org>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
---
 kernel/signal.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/signal.c b/kernel/signal.c
index 730ecd3d6faf..b113bf647fb4 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2349,6 +2349,10 @@ static bool do_signal_stop(int signr)
 
 		t = current;
 		while_each_thread(current, t) {
+			/* don't STOP PF_IO_WORKER threads */
+			if (t->flags & PF_IO_WORKER)
+				continue;
+
 			/*
 			 * Setting state to TASK_STOPPED for a group
 			 * stop is always done with the siglock held,
-- 
2.31.0