On 2/28/21 9:18 PM, syzbot wrote:

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in io_poll_double_wake

============================================
WARNING: possible recursive locking detected
5.11.0-syzkaller #0 Not tainted
--------------------------------------------
syz-executor.0/10241 is trying to acquire lock:
ffff888012e09130 (&runtime->sleep){..-.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline]
ffff888012e09130 (&runtime->sleep){..-.}-{2:2}, at: io_poll_double_wake+0x25f/0x6a0 fs/io_uring.c:4921

but task is already holding lock:
ffff888013b00130 (&runtime->sleep){..-.}-{2:2}, at: __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&runtime->sleep);
  lock(&runtime->sleep);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

Since the fix is in yet this keeps failing (and I didn't get it), I looked
closer at this report. While the names of the locks are the same, they are
really two different locks. So let's try this...

#syz test: git://git.kernel.dk/linux-block syzbot-test

-- 
Jens Axboe