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 690CEC4332F for ; Tue, 9 Nov 2021 22:43:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 568AC610CF for ; Tue, 9 Nov 2021 22:43:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346525AbhKIWqA (ORCPT ); Tue, 9 Nov 2021 17:46:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:59824 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344397AbhKIWlu (ORCPT ); Tue, 9 Nov 2021 17:41:50 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 26E2C61B32; Tue, 9 Nov 2021 22:23:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1636496635; bh=58wvV0nNtTfY2NbLUOQ9Odj5T5fmmH/wW4JaoLtaf5I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SgZiROlo9N/R5pXojMIH3kYFsLwPbDbQLERYG7PEg1jKkKJuDbWKt8ZB/IhixR71r W1MCMsG1uXlDhW0B+wJsFgv/joLJ3K3hfIarxZ3xYPOv9Wi7GCBjZF97SHU9MGbNMp Y0abB1MDHUCrFVyFa/QGgtoV27FfYQREMbmKj6vO8uoMNcwjmteXIF/eptpg8+N8OH QJIBdTqGVHppVOWN3DkWHX29qv3habMdxuhf9tA7LIJn8t8/THkw7fA0LVXL30iDmU HQ3S9gCBvAZgLy4UtgQCPXejhwGlucHWiBWmjk67aMrIlpeUescZ0VFyAi9bcTHrKD a8bsVI1xtP6gw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Guanghui Feng , Greg Kroah-Hartman , Sasha Levin , jslaby@suse.com Subject: [PATCH AUTOSEL 4.14 08/14] tty: tty_buffer: Fix the softlockup issue in flush_to_ldisc Date: Tue, 9 Nov 2021 17:23:37 -0500 Message-Id: <20211109222343.1235902-8-sashal@kernel.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20211109222343.1235902-1-sashal@kernel.org> References: <20211109222343.1235902-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Guanghui Feng [ Upstream commit 3968ddcf05fb4b9409cd1859feb06a5b0550a1c1 ] When running ltp testcase(ltp/testcases/kernel/pty/pty04.c) with arm64, there is a soft lockup, which look like this one: Workqueue: events_unbound flush_to_ldisc Call trace: dump_backtrace+0x0/0x1ec show_stack+0x24/0x30 dump_stack+0xd0/0x128 panic+0x15c/0x374 watchdog_timer_fn+0x2b8/0x304 __run_hrtimer+0x88/0x2c0 __hrtimer_run_queues+0xa4/0x120 hrtimer_interrupt+0xfc/0x270 arch_timer_handler_phys+0x40/0x50 handle_percpu_devid_irq+0x94/0x220 __handle_domain_irq+0x88/0xf0 gic_handle_irq+0x84/0xfc el1_irq+0xc8/0x180 slip_unesc+0x80/0x214 [slip] tty_ldisc_receive_buf+0x64/0x80 tty_port_default_receive_buf+0x50/0x90 flush_to_ldisc+0xbc/0x110 process_one_work+0x1d4/0x4b0 worker_thread+0x180/0x430 kthread+0x11c/0x120 In the testcase pty04, The first process call the write syscall to send data to the pty master. At the same time, the workqueue will do the flush_to_ldisc to pop data in a loop until there is no more data left. When the sender and workqueue running in different core, the sender sends data fastly in full time which will result in workqueue doing work in loop for a long time and occuring softlockup in flush_to_ldisc with kernel configured without preempt. So I add need_resched check and cond_resched in the flush_to_ldisc loop to avoid it. Signed-off-by: Guanghui Feng Link: https://lore.kernel.org/r/1633961304-24759-1-git-send-email-guanghuifeng@linux.alibaba.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/tty_buffer.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index cf11882d26025..a5b32dd056bef 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -528,6 +528,9 @@ static void flush_to_ldisc(struct work_struct *work) if (!count) break; head->read += count; + + if (need_resched()) + cond_resched(); } mutex_unlock(&buf->lock); -- 2.33.0