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io_uring/io-wq: don't trigger hung task for syzbot craziness

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Use the same trick that blk_io_schedule() does to avoid triggering the
hung task warning (and potential reboot/panic, depending on system
settings), and only wait for half the hung task timeout at the time.
If we exceed the default IO_URING_EXIT_WAIT_MAX period where we expect
things to certainly have finished unless there's a bug, then throw a
WARN_ON_ONCE() for that case.

Reported-by: syzbot+4eb282331cab6d5b6588@syzkaller.appspotmail.com
Tested-by: syzbot+4eb282331cab6d5b6588@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2026-01-21 10:40:33 -07:00
parent dd120bddc4
commit 1f293098a3
1 changed files with 21 additions and 1 deletions
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22
io_uring/io-wq.c
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@@ -17,6 +17,7 @@
#include <linux/task_work.h>
#include <linux/audit.h>
#include <linux/mmu_context.h>
#include <linux/sched/sysctl.h>
#include <uapi/linux/io_uring.h>
#include "io-wq.h"
@@ -1316,6 +1317,8 @@ static void io_wq_cancel_tw_create(struct io_wq *wq)
static void io_wq_exit_workers(struct io_wq *wq)
{
unsigned long timeout, warn_timeout;
if (!wq->task)
return;
@@ -1325,7 +1328,24 @@ static void io_wq_exit_workers(struct io_wq *wq)
io_wq_for_each_worker(wq, io_wq_worker_wake, NULL);
rcu_read_unlock();
io_worker_ref_put(wq);
wait_for_completion(&wq->worker_done);
/*
* Shut up hung task complaint, see for example
*
* https://lore.kernel.org/all/696fc9e7.a70a0220.111c58.0006.GAE@google.com/
*
* where completely overloading the system with tons of long running
* io-wq items can easily trigger the hung task timeout. Only sleep
* uninterruptibly for half that time, and warn if we exceeded end
* up waiting more than IO_URING_EXIT_WAIT_MAX.
*/
timeout = sysctl_hung_task_timeout_secs * HZ / 2;
warn_timeout = jiffies + IO_URING_EXIT_WAIT_MAX;
do {
if (wait_for_completion_timeout(&wq->worker_done, timeout))
break;
WARN_ON_ONCE(time_after(jiffies, warn_timeout));
} while (1);
spin_lock_irq(&wq->hash->wait.lock);
list_del_init(&wq->wait.entry);