Messages in this thread Patch in this message | | | Date | Fri, 22 Oct 2021 14:57:04 +0100 | Subject | Re: [syzbot] INFO: task hung in io_wqe_worker | From | Pavel Begunkov <> |
| |
On 10/22/21 14:49, Pavel Begunkov wrote: > On 10/22/21 05:38, syzbot wrote: >> Hello, >> >> syzbot has tested the proposed patch but the reproducer is still triggering an issue: >> INFO: task hung in io_wqe_worker >> >> INFO: task iou-wrk-9392:9401 blocked for more than 143 seconds. >> Not tainted 5.15.0-rc2-syzkaller #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:iou-wrk-9392 state:D stack:27952 pid: 9401 ppid: 7038 flags:0x00004004 >> Call Trace: >> context_switch kernel/sched/core.c:4940 [inline] >> __schedule+0xb44/0x5960 kernel/sched/core.c:6287 >> schedule+0xd3/0x270 kernel/sched/core.c:6366 >> schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1857 >> do_wait_for_common kernel/sched/completion.c:85 [inline] >> __wait_for_common kernel/sched/completion.c:106 [inline] >> wait_for_common kernel/sched/completion.c:117 [inline] >> wait_for_completion+0x176/0x280 kernel/sched/completion.c:138 >> io_worker_exit fs/io-wq.c:183 [inline] >> io_wqe_worker+0x66d/0xc40 fs/io-wq.c:597 >> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 > > Easily reproducible, it's stuck in > > static void io_worker_exit(struct io_worker *worker) > { > ... > wait_for_completion(&worker->ref_done); > ... > } > > The reference belongs to a create_worker_cb() task_work item. It's expected > to either be executed or cancelled by io_wq_exit_workers(), but the owner > task never goes __io_uring_cancel (called in do_exit()) and so never > reaches io_wq_exit_workers(). > > Following the owner task, cat /proc/<pid>/stack: > > [<0>] do_coredump+0x1d0/0x10e0 > [<0>] get_signal+0x4a3/0x960 > [<0>] arch_do_signal_or_restart+0xc3/0x6d0 > [<0>] exit_to_user_mode_prepare+0x10e/0x190 > [<0>] irqentry_exit_to_user_mode+0x9/0x20 > [<0>] irqentry_exit+0x36/0x40 > [<0>] exc_page_fault+0x95/0x190 > [<0>] asm_exc_page_fault+0x1e/0x30 > > (gdb) l *(do_coredump+0x1d0-5) > 0xffffffff81343ccb is in do_coredump (fs/coredump.c:469). > 464 > 465 if (core_waiters > 0) { > 466 struct core_thread *ptr; > 467 > 468 freezer_do_not_count(); > 469 wait_for_completion(&core_state->startup); > 470 freezer_count(); > > Can't say anything more at the moment as not familiar with coredump
A simple hack allowing task works to be executed from there workarounds the problem
diff --git a/fs/coredump.c b/fs/coredump.c index 3224dee44d30..f6f9dfb02296 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -466,7 +466,8 @@ static int coredump_wait(int exit_code, struct core_state *core_state) struct core_thread *ptr; freezer_do_not_count(); - wait_for_completion(&core_state->startup); + while (wait_for_completion_interruptible(&core_state->startup)) + tracehook_notify_signal(); freezer_count(); /* * Wait for all the threads to become inactive, so that
-- Pavel Begunkov
| |