The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 6195ba09822c87cad09189bbf550d0fbe714687a Mon Sep 17 00:00:00 2001
From: Hao Xu haoxu@linux.alibaba.com Date: Wed, 27 Jan 2021 15:14:09 +0800 Subject: [PATCH] io_uring: fix flush cqring overflow list while TASK_INTERRUPTIBLE
Abaci reported the follow warning:
[ 27.073425] do not call blocking ops when !TASK_RUNNING; state=1 set at [] prepare_to_wait_exclusive+0x3a/0xc0 [ 27.075805] WARNING: CPU: 0 PID: 951 at kernel/sched/core.c:7853 __might_sleep+0x80/0xa0 [ 27.077604] Modules linked in: [ 27.078379] CPU: 0 PID: 951 Comm: a.out Not tainted 5.11.0-rc3+ #1 [ 27.079637] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 [ 27.080852] RIP: 0010:__might_sleep+0x80/0xa0 [ 27.081835] Code: 65 48 8b 04 25 80 71 01 00 48 8b 90 c0 15 00 00 48 8b 70 18 48 c7 c7 08 39 95 82 c6 05 f9 5f de 08 01 48 89 d1 e8 00 c6 fa ff 0b eb bf 41 0f b6 f5 48 c7 c7 40 23 c9 82 e8 f3 48 ec 00 eb a7 [ 27.084521] RSP: 0018:ffffc90000fe3ce8 EFLAGS: 00010286 [ 27.085350] RAX: 0000000000000000 RBX: ffffffff82956083 RCX: 0000000000000000 [ 27.086348] RDX: ffff8881057a0000 RSI: ffffffff8118cc9e RDI: ffff88813bc28570 [ 27.087598] RBP: 00000000000003a7 R08: 0000000000000001 R09: 0000000000000001 [ 27.088819] R10: ffffc90000fe3e00 R11: 00000000fffef9f0 R12: 0000000000000000 [ 27.089819] R13: 0000000000000000 R14: ffff88810576eb80 R15: ffff88810576e800 [ 27.091058] FS: 00007f7b144cf740(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000 [ 27.092775] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 27.093796] CR2: 00000000022da7b8 CR3: 000000010b928002 CR4: 00000000003706f0 [ 27.094778] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 27.095780] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 27.097011] Call Trace: [ 27.097685] __mutex_lock+0x5d/0xa30 [ 27.098565] ? prepare_to_wait_exclusive+0x71/0xc0 [ 27.099412] ? io_cqring_overflow_flush.part.101+0x6d/0x70 [ 27.100441] ? lockdep_hardirqs_on_prepare+0xe9/0x1c0 [ 27.101537] ? _raw_spin_unlock_irqrestore+0x2d/0x40 [ 27.102656] ? trace_hardirqs_on+0x46/0x110 [ 27.103459] ? io_cqring_overflow_flush.part.101+0x6d/0x70 [ 27.104317] io_cqring_overflow_flush.part.101+0x6d/0x70 [ 27.105113] io_cqring_wait+0x36e/0x4d0 [ 27.105770] ? find_held_lock+0x28/0xb0 [ 27.106370] ? io_uring_remove_task_files+0xa0/0xa0 [ 27.107076] __x64_sys_io_uring_enter+0x4fb/0x640 [ 27.107801] ? rcu_read_lock_sched_held+0x59/0xa0 [ 27.108562] ? lockdep_hardirqs_on_prepare+0xe9/0x1c0 [ 27.109684] ? syscall_enter_from_user_mode+0x26/0x70 [ 27.110731] do_syscall_64+0x2d/0x40 [ 27.111296] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 27.112056] RIP: 0033:0x7f7b13dc8239 [ 27.112663] Code: 01 00 48 81 c4 80 00 00 00 e9 f1 fe ff ff 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 3d 01 f0 ff ff 73 01 c3 48 8b 0d 27 ec 2c 00 f7 d8 64 89 01 48 [ 27.115113] RSP: 002b:00007ffd6d7f5c88 EFLAGS: 00000286 ORIG_RAX: 00000000000001aa [ 27.116562] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f7b13dc8239 [ 27.117961] RDX: 000000000000478e RSI: 0000000000000000 RDI: 0000000000000003 [ 27.118925] RBP: 00007ffd6d7f5cb0 R08: 0000000020000040 R09: 0000000000000008 [ 27.119773] R10: 0000000000000001 R11: 0000000000000286 R12: 0000000000400480 [ 27.120614] R13: 00007ffd6d7f5d90 R14: 0000000000000000 R15: 0000000000000000 [ 27.121490] irq event stamp: 5635 [ 27.121946] hardirqs last enabled at (5643): [] console_unlock+0x5c4/0x740 [ 27.123476] hardirqs last disabled at (5652): [] console_unlock+0x4e7/0x740 [ 27.125192] softirqs last enabled at (5272): [] __do_softirq+0x3c5/0x5aa [ 27.126430] softirqs last disabled at (5267): [] asm_call_irq_on_stack+0xf/0x20 [ 27.127634] ---[ end trace 289d7e28fa60f928 ]---
This is caused by calling io_cqring_overflow_flush() which may sleep after calling prepare_to_wait_exclusive() which set task state to TASK_INTERRUPTIBLE
Reported-by: Abaci abaci@linux.alibaba.com Fixes: 6c503150ae33 ("io_uring: patch up IOPOLL overflow_flush sync") Reviewed-by: Pavel Begunkov asml.silence@gmail.com Signed-off-by: Hao Xu haoxu@linux.alibaba.com Signed-off-by: Jens Axboe axboe@kernel.dk
diff --git a/fs/io_uring.c b/fs/io_uring.c index c218deaf73a9..ae388cc52843 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -7268,14 +7268,18 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, TASK_INTERRUPTIBLE); /* make sure we run task_work before checking for signals */ ret = io_run_task_work_sig(); - if (ret > 0) + if (ret > 0) { + finish_wait(&ctx->wait, &iowq.wq); continue; + } else if (ret < 0) break; if (io_should_wake(&iowq)) break; - if (test_bit(0, &ctx->cq_check_overflow)) + if (test_bit(0, &ctx->cq_check_overflow)) { + finish_wait(&ctx->wait, &iowq.wq); continue; + } if (uts) { timeout = schedule_timeout(timeout); if (timeout == 0) {