From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0A919C433E0 for ; Sun, 3 Jan 2021 21:54:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C287B20782 for ; Sun, 3 Jan 2021 21:54:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726701AbhACVyT (ORCPT ); Sun, 3 Jan 2021 16:54:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47292 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726074AbhACVyS (ORCPT ); Sun, 3 Jan 2021 16:54:18 -0500 Received: from mail-pj1-x1031.google.com (mail-pj1-x1031.google.com [IPv6:2607:f8b0:4864:20::1031]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A033FC0613C1 for ; Sun, 3 Jan 2021 13:53:38 -0800 (PST) Received: by mail-pj1-x1031.google.com with SMTP id lb18so8589890pjb.5 for ; Sun, 03 Jan 2021 13:53:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=SOqNdsnqAMqhnVr3MpJKK4X9DOOmp6814kfWnP9S4FM=; b=y1cdXFGZJpYOh6kKX1ouuWSEilCExSz9gYHJ17RezGNA/EBig5DR8biiZGQ4rpGNct 84MUcwh0/tba3K7LqfC/lcL2DjJZnm+5v1GgbZjD3jUONljic/IGEPgqMXLn+PxlmQG5 uFzNAC9H2TU6buFlKO5fgSlWKK2KthjIGCHjZNEzMuabjwU/0MnyQq185SBoH7wREmoh MfWh5ApELl6ld4c5QvbfdF2y38tFJzDPMFokc0wnQrB14WkKDzB4izb2ef3DPiima6Rd UkeOpyNw5diJEwiqfEEmLTqy6GicK7lCJwdogwg6o6a18cy0oKyfQ+SJBE9IQQieHyQ3 G/hA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=SOqNdsnqAMqhnVr3MpJKK4X9DOOmp6814kfWnP9S4FM=; b=ssDWnET0FpFcd5G3FZS0Bi8oJ2sWOta+2M116QxXzARbsGYxNBXRT0TBOXh5ssVeRI Z8gi4NyX4Bna2wAyfl2Hh/E2CRnJfsCoC3ok9Eldo82ewL6PU2VEFYA2OH+Iu3bVk42/ BsHxszTIQIzlA40c4fuk0SR1ZiCQyTyWoJuyf1w9z3jGeqvkl6bNMfg3UYH0QmwiIybB Pa321tEdncj6l9iwsPKd4fTcSwEjGYzWbq9AZQNqi9Xd7Pq/XcoWp63x1Orj0FjQli5m IezAGJL/OaDNNiqxaIj8v3MVB1ARh2+Kop0WwBmhiRsPS7odbp1OMMJwaSK9jc0wSwB4 wUfg== X-Gm-Message-State: AOAM531l1GNCxfIgv4SittEChSJQH5ov4mx6++DmZGAiagcwU1r+UHN0 jyUzMG219JvQ+Hvg8BhFJwfuCQ== X-Google-Smtp-Source: ABdhPJzcd8BBndSAfUu2cIdM/q7zeKNDdn3Zp84q+JXRLH44Np6UcYZ63lGG/K661Ig5IZzidwyodg== X-Received: by 2002:a17:90a:a394:: with SMTP id x20mr26316806pjp.24.1609710818032; Sun, 03 Jan 2021 13:53:38 -0800 (PST) Received: from [192.168.1.134] ([66.219.217.173]) by smtp.gmail.com with ESMTPSA id c10sm54804651pfj.54.2021.01.03.13.53.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 03 Jan 2021 13:53:37 -0800 (PST) Subject: Re: INFO: task hung in __io_uring_task_cancel To: Palash Oswal , io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@kernel.org, mingo@redhat.com, peterz@infradead.org, rostedt@goodmis.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk, will@kernel.org References: From: Jens Axboe Message-ID: Date: Sun, 3 Jan 2021 14:53:35 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/2/21 9:14 PM, Palash Oswal wrote: > Hello, > > I was running syzkaller and I found the following issue : > > Head Commit : b1313fe517ca3703119dcc99ef3bbf75ab42bcfb ( v5.10.4 ) > Git Tree : stable > Console Output : > [ 242.769080] INFO: task repro:2639 blocked for more than 120 seconds. > [ 242.769096] Not tainted 5.10.4 #8 > [ 242.769103] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" > disables this message. > [ 242.769112] task:repro state:D stack: 0 pid: 2639 > ppid: 2638 flags:0x00000004 > [ 242.769126] Call Trace: > [ 242.769148] __schedule+0x28d/0x7e0 > [ 242.769162] ? __percpu_counter_sum+0x75/0x90 > [ 242.769175] schedule+0x4f/0xc0 > [ 242.769187] __io_uring_task_cancel+0xad/0xf0 > [ 242.769198] ? wait_woken+0x80/0x80 > [ 242.769210] bprm_execve+0x67/0x8a0 > [ 242.769223] do_execveat_common+0x1d2/0x220 > [ 242.769235] __x64_sys_execveat+0x5d/0x70 > [ 242.769249] do_syscall_64+0x38/0x90 > [ 242.769260] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ 242.769270] RIP: 0033:0x7f59ce45967d > [ 242.769277] RSP: 002b:00007ffd05d10a58 EFLAGS: 00000246 ORIG_RAX: > 0000000000000142 > [ 242.769290] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f59ce45967d > [ 242.769297] RDX: 0000000000000000 RSI: 0000000020000180 RDI: 00000000ffffffff > [ 242.769304] RBP: 00007ffd05d10a70 R08: 0000000000000000 R09: 00007ffd05d10a70 > [ 242.769311] R10: 0000000000000000 R11: 0000000000000246 R12: 000055a91d37d320 > [ 242.769318] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 Can you see if this helps? The reproducer is pretty brutal, it'll fork thousands of tasks with rings! But should work of course. I think this one is pretty straight forward, and actually an older issue with the poll rewaiting. diff --git a/fs/io_uring.c b/fs/io_uring.c index ca46f314640b..539de04f9183 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5103,6 +5103,12 @@ static bool io_poll_rewait(struct io_kiocb *req, struct io_poll_iocb *poll) { struct io_ring_ctx *ctx = req->ctx; + /* Never re-wait on poll if the ctx or task is going away */ + if (percpu_ref_is_dying(&ctx->refs) || req->task->flags & PF_EXITING) { + spin_lock_irq(&ctx->completion_lock); + return false; + } + if (!req->result && !READ_ONCE(poll->canceled)) { struct poll_table_struct pt = { ._key = poll->events }; -- Jens Axboe