Commits
Jackie Liu committed a4c0b3decb3
io_uring: fix io_sq_thread_stop running in front of io_sq_thread
INFO: task syz-executor.5:8634 blocked for more than 143 seconds.
Not tainted 5.2.0-rc5+ #3
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D25632 8634 8224 0x00004004
Call Trace:
context_switch kernel/sched/core.c:2818 [inline]
__schedule+0x658/0x9e0 kernel/sched/core.c:3445
schedule+0x131/0x1d0 kernel/sched/core.c:3509
schedule_timeout+0x9a/0x2b0 kernel/time/timer.c:1783
do_wait_for_common+0x35e/0x5a0 kernel/sched/completion.c:83
__wait_for_common kernel/sched/completion.c:104 [inline]
wait_for_common kernel/sched/completion.c:115 [inline]
wait_for_completion+0x47/0x60 kernel/sched/completion.c:136
kthread_stop+0xb4/0x150 kernel/kthread.c:559
io_sq_thread_stop fs/io_uring.c:2252 [inline]
io_finish_async fs/io_uring.c:2259 [inline]
io_ring_ctx_free fs/io_uring.c:2770 [inline]
io_ring_ctx_wait_and_kill+0x268/0x880 fs/io_uring.c:2834
io_uring_release+0x5d/0x70 fs/io_uring.c:2842
__fput+0x2e4/0x740 fs/file_table.c:280
____fput+0x15/0x20 fs/file_table.c:313
task_work_run+0x17e/0x1b0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:185 [inline]
exit_to_usermode_loop arch/x86/entry/common.c:168 [inline]
prepare_exit_to_usermode+0x402/0x4f0 arch/x86/entry/common.c:199
syscall_return_slowpath+0x110/0x440 arch/x86/entry/common.c:279
do_syscall_64+0x126/0x140 arch/x86/entry/common.c:304
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x412fb1
Code: 80 3b 7c 0f 84 c7 02 00 00 c7 85 d0 00 00 00 00 00 00 00 48 8b 05 cf
a6 24 00 49 8b 14 24 41 b9 cb 2a 44 00 48 89 ee 48 89 df <48> 85 c0 4c 0f
45 c8 45 31 c0 31 c9 e8 0e 5b 00 00 85 c0 41 89 c7
RSP: 002b:00007ffe7ee6a180 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000412fb1
RDX: 0000001b2d920000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00000000f3a3e1f8 R09: 00000000f3a3e1fc
R10: 00007ffe7ee6a260 R11: 0000000000000293 R12: 000000000075c9a0
R13: 000000000075c9a0 R14: 0000000000024c00 R15: 000000000075bf2c
=============================================
There is an wrong logic, when kthread_park running
in front of io_sq_thread.
CPU#0 CPU#1
io_sq_thread_stop: int kthread(void *_create):
kthread_park()
__kthread_parkme(self); <<< Wrong
kthread_stop()
<< wait for self->exited
<< clear_bit KTHREAD_SHOULD_PARK
ret = threadfn(data);
|
|- io_sq_thread
|- kthread_should_park() << false
|- schedule() <<< nobody wake up
stuck CPU#0 stuck CPU#1
So, use a new variable sqo_thread_started to ensure that io_sq_thread
run first, then io_sq_thread_stop.
Reported-by: syzbot+94324416c485d422fe15@syzkaller.appspotmail.com
Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>