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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_GIT 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 1CF60C433E0 for ; Thu, 18 Feb 2021 15:41:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C7C0A64E85 for ; Thu, 18 Feb 2021 15:41:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231965AbhBRPlE (ORCPT ); Thu, 18 Feb 2021 10:41:04 -0500 Received: from out30-133.freemail.mail.aliyun.com ([115.124.30.133]:44780 "EHLO out30-133.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231841AbhBROlF (ORCPT ); Thu, 18 Feb 2021 09:41:05 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R271e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=haoxu@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0UOu49qy_1613659210; Received: from e18g09479.et15sqa.tbsite.net(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0UOu49qy_1613659210) by smtp.aliyun-inc.com(127.0.0.1); Thu, 18 Feb 2021 22:40:18 +0800 From: Hao Xu To: Jens Axboe Cc: io-uring@vger.kernel.org, Pavel Begunkov , Joseph Qi , Hao Xu Subject: [PATCH v2 5.12] io_uring: don't hold uring_lock when calling io_run_task_work* Date: Thu, 18 Feb 2021 22:39:59 +0800 Message-Id: <1613659199-14196-1-git-send-email-haoxu@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Abaci reported the below issue: [ 141.400455] hrtimer: interrupt took 205853 ns [ 189.869316] process 'usr/local/ilogtail/ilogtail_0.16.26' started with executable stack [ 250.188042] [ 250.188327] ============================================ [ 250.189015] WARNING: possible recursive locking detected [ 250.189732] 5.11.0-rc4 #1 Not tainted [ 250.190267] -------------------------------------------- [ 250.190917] a.out/7363 is trying to acquire lock: [ 250.191506] ffff888114dbcbe8 (&ctx->uring_lock){+.+.}-{3:3}, at: __io_req_task_submit+0x29/0xa0 [ 250.192599] [ 250.192599] but task is already holding lock: [ 250.193309] ffff888114dbfbe8 (&ctx->uring_lock){+.+.}-{3:3}, at: __x64_sys_io_uring_register+0xad/0x210 [ 250.194426] [ 250.194426] other info that might help us debug this: [ 250.195238] Possible unsafe locking scenario: [ 250.195238] [ 250.196019] CPU0 [ 250.196411] ---- [ 250.196803] lock(&ctx->uring_lock); [ 250.197420] lock(&ctx->uring_lock); [ 250.197966] [ 250.197966] *** DEADLOCK *** [ 250.197966] [ 250.198837] May be due to missing lock nesting notation [ 250.198837] [ 250.199780] 1 lock held by a.out/7363: [ 250.200373] #0: ffff888114dbfbe8 (&ctx->uring_lock){+.+.}-{3:3}, at: __x64_sys_io_uring_register+0xad/0x210 [ 250.201645] [ 250.201645] stack backtrace: [ 250.202298] CPU: 0 PID: 7363 Comm: a.out Not tainted 5.11.0-rc4 #1 [ 250.203144] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 [ 250.203887] Call Trace: [ 250.204302] dump_stack+0xac/0xe3 [ 250.204804] __lock_acquire+0xab6/0x13a0 [ 250.205392] lock_acquire+0x2c3/0x390 [ 250.205928] ? __io_req_task_submit+0x29/0xa0 [ 250.206541] __mutex_lock+0xae/0x9f0 [ 250.207071] ? __io_req_task_submit+0x29/0xa0 [ 250.207745] ? 0xffffffffa0006083 [ 250.208248] ? __io_req_task_submit+0x29/0xa0 [ 250.208845] ? __io_req_task_submit+0x29/0xa0 [ 250.209452] ? __io_req_task_submit+0x5/0xa0 [ 250.210083] __io_req_task_submit+0x29/0xa0 [ 250.210687] io_async_task_func+0x23d/0x4c0 [ 250.211278] task_work_run+0x89/0xd0 [ 250.211884] io_run_task_work_sig+0x50/0xc0 [ 250.212464] io_sqe_files_unregister+0xb2/0x1f0 [ 250.213109] __io_uring_register+0x115a/0x1750 [ 250.213718] ? __x64_sys_io_uring_register+0xad/0x210 [ 250.214395] ? __fget_files+0x15a/0x260 [ 250.214956] __x64_sys_io_uring_register+0xbe/0x210 [ 250.215620] ? trace_hardirqs_on+0x46/0x110 [ 250.216205] do_syscall_64+0x2d/0x40 [ 250.216731] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 250.217455] RIP: 0033:0x7f0fa17e5239 [ 250.218034] 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 [ 250.220343] RSP: 002b:00007f0fa1eeac48 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab [ 250.221360] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f0fa17e5239 [ 250.222272] RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000008 [ 250.223185] RBP: 00007f0fa1eeae20 R08: 0000000000000000 R09: 0000000000000000 [ 250.224091] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [ 250.224999] R13: 0000000000021000 R14: 0000000000000000 R15: 00007f0fa1eeb700 This is caused by calling io_run_task_work_sig() to do work under uring_lock while the caller io_sqe_files_unregister() already held uring_lock. To fix this issue, briefly drop uring_lock when calling io_run_task_work_sig(), and there are two things to concern: - hold uring_lock in io_ring_ctx_free() when calling io_sqe_files_unregister() this is for consistency of lock/unlock. - add new fixed file ref node before dropping uring_lock it's not safe to do io_uring_enter-->percpu_ref_get() with a dying one. - check if file_data->refs is dying to avoid parallel io_sqe_files_unregister Reported-by: Abaci Fixes: 1ffc54220c44 ("io_uring: fix io_sqe_files_unregister() hangs") Suggested-by: Pavel Begunkov Signed-off-by: Hao Xu --- fs/io_uring.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 52 insertions(+), 13 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 1f68105a41ed..4521d04adee7 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -7342,25 +7342,49 @@ static void io_sqe_files_set_node(struct fixed_file_data *file_data, percpu_ref_get(&file_data->refs); } -static int io_sqe_files_unregister(struct io_ring_ctx *ctx) +static int fixed_file_ref_node_add(struct io_ring_ctx *ctx) { struct fixed_file_data *data = ctx->file_data; - struct fixed_file_ref_node *backup_node, *ref_node = NULL; - unsigned nr_tables, i; - int ret; + struct fixed_file_ref_node *backup_node; - if (!data) - return -ENXIO; backup_node = alloc_fixed_file_ref_node(ctx); if (!backup_node) return -ENOMEM; + io_sqe_files_set_node(data, backup_node); + + return 0; +} +static void fixed_file_ref_node_kill(struct fixed_file_data *data) +{ + struct fixed_file_ref_node *ref_node = NULL; spin_lock_bh(&data->lock); ref_node = data->node; spin_unlock_bh(&data->lock); if (ref_node) percpu_ref_kill(&ref_node->refs); +} + +static int io_sqe_files_unregister(struct io_ring_ctx *ctx) +{ + struct fixed_file_data *data = ctx->file_data; + struct fixed_file_ref_node *backup_node; + unsigned nr_tables, i; + int ret; + + /* + * percpu_ref_is_dying() is to stop parallel files unregister + * Since we possibly drop uring lock later in this function to + * run task work. + */ + if (!data || percpu_ref_is_dying(&data->refs)) + return -ENXIO; + backup_node = alloc_fixed_file_ref_node(ctx); + if (!backup_node) + return -ENOMEM; + + fixed_file_ref_node_kill(data); percpu_ref_kill(&data->refs); /* wait for all refs nodes to complete */ @@ -7369,14 +7393,27 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx) ret = wait_for_completion_interruptible(&data->done); if (!ret) break; + + ret = fixed_file_ref_node_add(ctx); + if (ret < 0) + break; + /* + * There is small possibility that data->done is already completed + * So reinit it here + */ + reinit_completion(&data->done); + mutex_unlock(&ctx->uring_lock); ret = io_run_task_work_sig(); - if (ret < 0) { - percpu_ref_resurrect(&data->refs); - reinit_completion(&data->done); - io_sqe_files_set_node(data, backup_node); - return ret; - } - } while (1); + mutex_lock(&ctx->uring_lock); + fixed_file_ref_node_kill(data); + } while (ret >= 0); + + if (ret < 0) { + percpu_ref_resurrect(&data->refs); + reinit_completion(&data->done); + io_sqe_files_set_node(data, backup_node); + return ret; + } __io_sqe_files_unregister(ctx); nr_tables = DIV_ROUND_UP(ctx->nr_user_files, IORING_MAX_FILES_TABLE); @@ -8685,7 +8722,9 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx) css_put(ctx->sqo_blkcg_css); #endif + mutex_lock(&ctx->uring_lock); io_sqe_files_unregister(ctx); + mutex_unlock(&ctx->uring_lock); io_eventfd_unregister(ctx); io_destroy_buffers(ctx); idr_destroy(&ctx->personality_idr); -- 1.8.3.1