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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C3E4C433EF for ; Mon, 15 Nov 2021 23:28:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 17993613AD for ; Mon, 15 Nov 2021 23:28:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350031AbhKOXay (ORCPT ); Mon, 15 Nov 2021 18:30:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:44642 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245246AbhKOTTy (ORCPT ); Mon, 15 Nov 2021 14:19:54 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 33D496351A; Mon, 15 Nov 2021 18:31:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1637001068; bh=rxsXMyQBQe1V/ux9QLvBgUcCTn+GCc8WADOopU+D3sE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=d7VZ1Q+CoXqHQQTAyiIx+70tkK00CsLC0er7ZpTnx2VM6bjPP7IVV4zQs+6PZMtxB 0tloPgZv8jE/Emd6EkM7ifOD9RcNT7UlfBRl2NWncv6ji68l/PmUXChHqWyBEr/dXs ZIwVuvj3cRs/kXMnQK9nT/i1Pm+FhKy03x5bnlSA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pavel Begunkov , Jens Axboe , syzbot+27d62ee6f256b186883e@syzkaller.appspotmail.com Subject: [PATCH 5.15 021/917] io-wq: remove worker to owner tw dependency Date: Mon, 15 Nov 2021 17:51:56 +0100 Message-Id: <20211115165429.448792346@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211115165428.722074685@linuxfoundation.org> References: <20211115165428.722074685@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Pavel Begunkov commit 1d5f5ea7cb7d15b9fb1cc82673ebb054f02cd7d2 upstream. INFO: task iou-wrk-6609:6612 blocked for more than 143 seconds. Not tainted 5.15.0-rc5-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:iou-wrk-6609 state:D stack:27944 pid: 6612 ppid: 6526 flags:0x00004006 Call Trace: context_switch kernel/sched/core.c:4940 [inline] __schedule+0xb44/0x5960 kernel/sched/core.c:6287 schedule+0xd3/0x270 kernel/sched/core.c:6366 schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1857 do_wait_for_common kernel/sched/completion.c:85 [inline] __wait_for_common kernel/sched/completion.c:106 [inline] wait_for_common kernel/sched/completion.c:117 [inline] wait_for_completion+0x176/0x280 kernel/sched/completion.c:138 io_worker_exit fs/io-wq.c:183 [inline] io_wqe_worker+0x66d/0xc40 fs/io-wq.c:597 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 io-wq worker may submit a task_work to the master task and upon io_worker_exit() wait for the tw to get executed. The problem appears when the master task is waiting in coredump.c: 468 freezer_do_not_count(); 469 wait_for_completion(&core_state->startup); 470 freezer_count(); Apparently having some dependency on children threads getting everything stuck. Workaround it by cancelling the taks_work callback that causes it before going into io_worker_exit() waiting. p.s. probably a better option is to not submit tw elevating the refcount in the first place, but let's leave this excercise for the future. Cc: stable@vger.kernel.org Reported-and-tested-by: syzbot+27d62ee6f256b186883e@syzkaller.appspotmail.com Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/r/142a716f4ed936feae868959059154362bfa8c19.1635509451.git.asml.silence@gmail.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- fs/io-wq.c | 46 +++++++++++++++++++++++++++++++++++++--------- 1 file changed, 37 insertions(+), 9 deletions(-) --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -140,6 +140,7 @@ static void io_wqe_dec_running(struct io static bool io_acct_cancel_pending_work(struct io_wqe *wqe, struct io_wqe_acct *acct, struct io_cb_cancel_data *match); +static void create_worker_cb(struct callback_head *cb); static bool io_worker_get(struct io_worker *worker) { @@ -174,9 +175,44 @@ static void io_worker_ref_put(struct io_ complete(&wq->worker_done); } +static void io_worker_cancel_cb(struct io_worker *worker) +{ + struct io_wqe_acct *acct = io_wqe_get_acct(worker); + struct io_wqe *wqe = worker->wqe; + struct io_wq *wq = wqe->wq; + + atomic_dec(&acct->nr_running); + raw_spin_lock(&worker->wqe->lock); + acct->nr_workers--; + raw_spin_unlock(&worker->wqe->lock); + io_worker_ref_put(wq); + clear_bit_unlock(0, &worker->create_state); + io_worker_release(worker); +} + +static bool io_task_worker_match(struct callback_head *cb, void *data) +{ + struct io_worker *worker; + + if (cb->func != create_worker_cb) + return false; + worker = container_of(cb, struct io_worker, create_work); + return worker == data; +} + static void io_worker_exit(struct io_worker *worker) { struct io_wqe *wqe = worker->wqe; + struct io_wq *wq = wqe->wq; + + while (1) { + struct callback_head *cb = task_work_cancel_match(wq->task, + io_task_worker_match, worker); + + if (!cb) + break; + io_worker_cancel_cb(worker); + } if (refcount_dec_and_test(&worker->ref)) complete(&worker->ref_done); @@ -1150,17 +1186,9 @@ static void io_wq_exit_workers(struct io while ((cb = task_work_cancel_match(wq->task, io_task_work_match, wq)) != NULL) { struct io_worker *worker; - struct io_wqe_acct *acct; worker = container_of(cb, struct io_worker, create_work); - acct = io_wqe_get_acct(worker); - atomic_dec(&acct->nr_running); - raw_spin_lock(&worker->wqe->lock); - acct->nr_workers--; - raw_spin_unlock(&worker->wqe->lock); - io_worker_ref_put(wq); - clear_bit_unlock(0, &worker->create_state); - io_worker_release(worker); + io_worker_cancel_cb(worker); } rcu_read_lock();