From: Jackie Liu liuyun01@kylinos.cn
[ Upstream commit a4c0b3decb33fb4a2b5ecc6234a50680f0b21e7d ]
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
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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 Signed-off-by: Sasha Levin sashal@kernel.org --- fs/io_uring.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/fs/io_uring.c b/fs/io_uring.c index 4ef62a45045d..fef2cd44b2ac 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -231,6 +231,7 @@ struct io_ring_ctx { struct task_struct *sqo_thread; /* if using sq thread polling */ struct mm_struct *sqo_mm; wait_queue_head_t sqo_wait; + struct completion sqo_thread_started;
struct { /* CQ ring */ @@ -403,6 +404,7 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p) ctx->flags = p->flags; init_waitqueue_head(&ctx->cq_wait); init_completion(&ctx->ctx_done); + init_completion(&ctx->sqo_thread_started); mutex_init(&ctx->uring_lock); init_waitqueue_head(&ctx->wait); for (i = 0; i < ARRAY_SIZE(ctx->pending_async); i++) { @@ -2009,6 +2011,8 @@ static int io_sq_thread(void *data) unsigned inflight; unsigned long timeout;
+ complete(&ctx->sqo_thread_started); + old_fs = get_fs(); set_fs(USER_DS);
@@ -2243,6 +2247,7 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx) static void io_sq_thread_stop(struct io_ring_ctx *ctx) { if (ctx->sqo_thread) { + wait_for_completion(&ctx->sqo_thread_started); /* * The park is a bit of a work-around, without it we get * warning spews on shutdown with SQPOLL set and affinity