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Thu, 18 Feb 2021 11:19:37 -0800 (PST) Subject: Re: [PATCH] io_uring: don't recursively hold ctx->uring_lock in io_wq_submit_work() To: Hao Xu , Jens Axboe Cc: io-uring@vger.kernel.org, Joseph Qi References: <1611394824-73078-1-git-send-email-haoxu@linux.alibaba.com> <45a0221a-bd2b-7183-e35d-2d2550f687b5@kernel.dk> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: Date: Thu, 18 Feb 2021 19:15:48 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 18/02/2021 17:16, Hao Xu wrote: > 在 2021/1/25 下午12:31, Jens Axboe 写道: >> On 1/23/21 2:40 AM, Hao Xu wrote: >>> Abaci reported the following warning: >>> >>> [   97.862205] ============================================ >>> [   97.863400] WARNING: possible recursive locking detected >>> [   97.864640] 5.11.0-rc4+ #12 Not tainted >>> [   97.865537] -------------------------------------------- >>> [   97.866748] a.out/2890 is trying to acquire lock: >>> [   97.867829] ffff8881046763e8 (&ctx->uring_lock){+.+.}-{3:3}, at: >>> io_wq_submit_work+0x155/0x240 >>> [   97.869735] >>> [   97.869735] but task is already holding lock: >>> [   97.871033] ffff88810dfe0be8 (&ctx->uring_lock){+.+.}-{3:3}, at: >>> __x64_sys_io_uring_enter+0x3f0/0x5b0 >>> [   97.873074] >>> [   97.873074] other info that might help us debug this: >>> [   97.874520]  Possible unsafe locking scenario: >>> [   97.874520] >>> [   97.875845]        CPU0 >>> [   97.876440]        ---- >>> [   97.877048]   lock(&ctx->uring_lock); >>> [   97.877961]   lock(&ctx->uring_lock); >>> [   97.878881] >>> [   97.878881]  *** DEADLOCK *** >>> [   97.878881] >>> [   97.880341]  May be due to missing lock nesting notation >>> [   97.880341] >>> [   97.881952] 1 lock held by a.out/2890: >>> [   97.882873]  #0: ffff88810dfe0be8 (&ctx->uring_lock){+.+.}-{3:3}, at: >>> __x64_sys_io_uring_enter+0x3f0/0x5b0 >>> [   97.885108] >>> [   97.885108] stack backtrace: >>> [   97.886209] CPU: 0 PID: 2890 Comm: a.out Not tainted 5.11.0-rc4+ #12 >>> [   97.887683] Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS >>> rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014 >>> [   97.890457] Call Trace: >>> [   97.891121]  dump_stack+0xac/0xe3 >>> [   97.891972]  __lock_acquire+0xab6/0x13a0 >>> [   97.892940]  lock_acquire+0x2c3/0x390 >>> [   97.893853]  ? io_wq_submit_work+0x155/0x240 >>> [   97.894894]  __mutex_lock+0xae/0x9f0 >>> [   97.895785]  ? io_wq_submit_work+0x155/0x240 >>> [   97.896816]  ? __lock_acquire+0x782/0x13a0 >>> [   97.897817]  ? io_wq_submit_work+0x155/0x240 >>> [   97.898867]  ? io_wq_submit_work+0x155/0x240 >>> [   97.899916]  ? _raw_spin_unlock_irqrestore+0x2d/0x40 >>> [   97.901101]  io_wq_submit_work+0x155/0x240 >>> [   97.902112]  io_wq_cancel_cb+0x162/0x490 >>> [   97.903084]  ? io_uring_get_socket+0x40/0x40 >>> [   97.904126]  io_async_find_and_cancel+0x3b/0x140 >>> [   97.905247]  io_issue_sqe+0x86d/0x13e0 >>> [   97.906186]  ? __lock_acquire+0x782/0x13a0 >>> [   97.907195]  ? __io_queue_sqe+0x10b/0x550 >>> [   97.908175]  ? lock_acquire+0x2c3/0x390 >>> [   97.909122]  __io_queue_sqe+0x10b/0x550 >>> [   97.910080]  ? io_req_prep+0xd8/0x1090 >>> [   97.911044]  ? mark_held_locks+0x5a/0x80 >>> [   97.912042]  ? mark_held_locks+0x5a/0x80 >>> [   97.913014]  ? io_queue_sqe+0x235/0x470 >>> [   97.913971]  io_queue_sqe+0x235/0x470 >>> [   97.914894]  io_submit_sqes+0xcce/0xf10 >>> [   97.915842]  ? xa_store+0x3b/0x50 >>> [   97.916683]  ? __x64_sys_io_uring_enter+0x3f0/0x5b0 >>> [   97.917872]  __x64_sys_io_uring_enter+0x3fb/0x5b0 >>> [   97.918995]  ? lockdep_hardirqs_on_prepare+0xde/0x180 >>> [   97.920204]  ? syscall_enter_from_user_mode+0x26/0x70 >>> [   97.921424]  do_syscall_64+0x2d/0x40 >>> [   97.922329]  entry_SYSCALL_64_after_hwframe+0x44/0xa9 >>> [   97.923538] RIP: 0033:0x7f0b62601239 >>> [   97.924437] 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 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 27 ec 2c 00 f7 d8 64 89 01 >>>        48 >>> [   97.928628] RSP: 002b:00007f0b62cc4d28 EFLAGS: 00000246 ORIG_RAX: >>> 00000000000001aa >>> [   97.930422] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: >>> 00007f0b62601239 >>> [   97.932073] RDX: 0000000000000000 RSI: 0000000000006cf6 RDI: >>> 0000000000000005 >>> [   97.933710] RBP: 00007f0b62cc4e20 R08: 0000000000000000 R09: >>> 0000000000000000 >>> [   97.935369] R10: 0000000000000000 R11: 0000000000000246 R12: >>> 0000000000000000 >>> [   97.937008] R13: 0000000000021000 R14: 0000000000000000 R15: >>> 00007f0b62cc5700 >>> >>> This is caused by try to hold uring_lock in io_wq_submit_work() without >>> checking if we are in io-wq thread context or not. It can be in original >>> context when io_wq_submit_work() is called from IORING_OP_ASYNC_CANCEL >>> code path, where we already held uring_lock. >> >> Looks like another fallout of the split CLOSE handling. I've got the >> right fixes pending for 5.12: >> >> https://git.kernel.dk/cgit/linux-block/commit/?h=for-5.12/io_uring&id=6bb0079ef3420041886afe1bcd8e7a87e08992e1 >> >> (and the prep patch before that in the tree). But that won't really >> help us for 5.11 and earlier, though we probably should just queue >> those two patches for 5.11 and get them into stable. I really don't >> like the below patch, though it should fix it. But the root cause >> is really the weird open cancelation... >> > Hi Jens, > I've repro-ed this issue on branch for-5.12/io_uring-2021-02-17 > which contains the patch you give, the issue still exists. > I think this one is not an async close specifical problem. > The rootcause is we try to run an iowq work in the original > context(queue an iowq work, then async cancel it). If you mean cancellation executed from task_work or inline (during submission), then yes, I agree. Can you try a diff below? diff --git a/fs/io_uring.c b/fs/io_uring.c index 2fdfe5fa00b0..8dab07f42b34 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -2337,7 +2337,9 @@ static void io_req_task_cancel(struct callback_head *cb) struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work); struct io_ring_ctx *ctx = req->ctx; + mutex_lock(&ctx->uring_lock); __io_req_task_cancel(req, -ECANCELED); + mutex_unlock(&ctx->uring_lock); percpu_ref_put(&ctx->refs); } @@ -6426,8 +6428,13 @@ static void io_wq_submit_work(struct io_wq_work *work) if (timeout) io_queue_linked_timeout(timeout); - if (work->flags & IO_WQ_WORK_CANCEL) - ret = -ECANCELED; + if (work->flags & IO_WQ_WORK_CANCEL) { + /* io-wq is going to take down one */ + refcount_inc(&req->refs); + percpu_ref_get(&req->ctx->refs); + io_req_task_work_add_fallback(req, io_req_task_cancel); + return; + } if (!ret) { do { -- 2.24.0