From patchwork Mon Aug 19 14:44:29 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Viresh Kumar X-Patchwork-Id: 19322 Return-Path: X-Original-To: linaro@patches.linaro.org Delivered-To: linaro@patches.linaro.org Received: from mail-gh0-f199.google.com (mail-gh0-f199.google.com [209.85.160.199]) by ip-10-151-82-157.ec2.internal (Postfix) with ESMTPS id F1BBE25E2C for ; Mon, 19 Aug 2013 14:47:40 +0000 (UTC) Received: by mail-gh0-f199.google.com with SMTP id g14sf5323973ghb.6 for ; Mon, 19 Aug 2013 07:47:40 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:x-gm-message-state:delivered-to:from:to:cc:subject :date:message-id:in-reply-to:references:in-reply-to:references :x-original-sender:x-original-authentication-results:precedence :mailing-list:list-id:list-post:list-help:list-archive :list-unsubscribe; bh=REYgB0i8yL6ptYtG0ig2Xe3RjmylizlT42Z4+KxBnRk=; b=g8rwAQrxDAzgNKzF+Rbl6MsexdTTUzcBmjb1wMUyEJka46CbFFcuHmM6Ck4Cnkkw+4 uU2EsUCfXxwNvOjaLCRHEiRzPxYzlWd+vC1yWH9QuRtRqtOPPK9dYk97Nx1jcG6WDd7i +QtLVrdfnNs5sY9fjgVAA8bVe9DNduNzEGcJVWnWwIi6gmDnF2eTw8dRfN1Iw2pRuClb mzoCVGApD2ACMcLM7jUYFu10YS5uQbygfI5InCqHSfYh3zqhZdrHqWR90rLD0uy5PRS5 IbZReRepKnCeMnToGEL9lYHBKViXsqx9hhd9VRI+6MG9RiAuZhpLX3m5pQR5nKp4dBzQ TbLw== X-Received: by 10.236.124.33 with SMTP id w21mr1981828yhh.15.1376923660686; Mon, 19 Aug 2013 07:47:40 -0700 (PDT) MIME-Version: 1.0 X-BeenThere: patchwork-forward@linaro.org Received: by 10.49.71.168 with SMTP id w8ls1797592qeu.64.gmail; Mon, 19 Aug 2013 07:47:40 -0700 (PDT) X-Received: by 10.220.47.10 with SMTP id l10mr419400vcf.32.1376923660558; Mon, 19 Aug 2013 07:47:40 -0700 (PDT) Received: from mail-ve0-f180.google.com (mail-ve0-f180.google.com [209.85.128.180]) by mx.google.com with ESMTPS id cu1si2431424vcb.61.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 19 Aug 2013 07:47:40 -0700 (PDT) Received-SPF: neutral (google.com: 209.85.128.180 is neither permitted nor denied by best guess record for domain of patch+caf_=patchwork-forward=linaro.org@linaro.org) client-ip=209.85.128.180; Received: by mail-ve0-f180.google.com with SMTP id pb11so2952090veb.25 for ; Mon, 19 Aug 2013 07:47:40 -0700 (PDT) X-Gm-Message-State: ALoCoQnHooDvli03a4e0ChR8IH6s++MeCUZQqrC97eAAgMMywknZO1xrT9crZe+jtII0FZmdZhp3 X-Received: by 10.58.100.234 with SMTP id fb10mr13913318veb.5.1376923660438; Mon, 19 Aug 2013 07:47:40 -0700 (PDT) X-Forwarded-To: patchwork-forward@linaro.org X-Forwarded-For: patch@linaro.org patchwork-forward@linaro.org Delivered-To: patches@linaro.org Received: by 10.220.174.196 with SMTP id u4csp100250vcz; Mon, 19 Aug 2013 07:47:39 -0700 (PDT) X-Received: by 10.68.250.5 with SMTP id yy5mr13848070pbc.93.1376923658470; Mon, 19 Aug 2013 07:47:38 -0700 (PDT) Received: from mail-pd0-f170.google.com (mail-pd0-f170.google.com [209.85.192.170]) by mx.google.com with ESMTPS id zo6si8781188pac.257.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 19 Aug 2013 07:47:38 -0700 (PDT) Received-SPF: neutral (google.com: 209.85.192.170 is neither permitted nor denied by best guess record for domain of viresh.kumar@linaro.org) client-ip=209.85.192.170; Received: by mail-pd0-f170.google.com with SMTP id x10so5329861pdj.15 for ; Mon, 19 Aug 2013 07:47:38 -0700 (PDT) X-Received: by 10.66.25.133 with SMTP id c5mr13581434pag.4.1376923658042; Mon, 19 Aug 2013 07:47:38 -0700 (PDT) Received: from localhost ([122.172.193.46]) by mx.google.com with ESMTPSA id py4sm15576750pbb.33.1969.12.31.16.00.00 (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Mon, 19 Aug 2013 07:47:37 -0700 (PDT) From: Viresh Kumar To: gregkh@linuxfoundation.org, jslaby@suse.cz Cc: linaro-kernel@lists.linaro.org, patches@linaro.org, linux-serial@vger.kernel.org, Viresh Kumar , Tony Prisk Subject: [PATCH V2 25/25] tty: serial: vt8500: drop uart_port->lock before calling tty_flip_buffer_push() Date: Mon, 19 Aug 2013 20:14:29 +0530 Message-Id: X-Mailer: git-send-email 1.7.12.rc2.18.g61b472e In-Reply-To: References: In-Reply-To: References: X-Removed-Original-Auth: Dkim didn't pass. X-Original-Sender: viresh.kumar@linaro.org X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 209.85.128.180 is neither permitted nor denied by best guess record for domain of patch+caf_=patchwork-forward=linaro.org@linaro.org) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Precedence: list Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org List-ID: X-Google-Group-Id: 836684582541 List-Post: , List-Help: , List-Archive: List-Unsubscribe: , The current driver triggers a lockdep warning for if tty_flip_buffer_push() is called with uart_port->lock locked. This never shows up on UP kernels and comes up only on SMP kernels. Crash looks like this (produced with samsung.c driver): ----- [] (unwind_backtrace+0x0/0xf8) from [] (show_stack+0x10/0x14) [] (show_stack+0x10/0x14) from [] (dump_stack+0x6c/0xac) [] (dump_stack+0x6c/0xac) from [] (do_raw_spin_unlock+0xc4/0xd8) [] (do_raw_spin_unlock+0xc4/0xd8) from [] (_raw_spin_unlock_irqrestore+0xc/0) [] (_raw_spin_unlock_irqrestore+0xc/0x38) from [] (s3c24xx_serial_rx_chars+0) [] (s3c24xx_serial_rx_chars+0x12c/0x260) from [] (s3c64xx_serial_handle_irq+) [] (s3c64xx_serial_handle_irq+0x48/0x60) from [] (handle_irq_event_percpu+0x) [] (handle_irq_event_percpu+0x50/0x194) from [] (handle_irq_event+0x3c/0x5c) [] (handle_irq_event+0x3c/0x5c) from [] (handle_fasteoi_irq+0x80/0x13c) [] (handle_fasteoi_irq+0x80/0x13c) from [] (generic_handle_irq+0x20/0x30) [] (generic_handle_irq+0x20/0x30) from [] (handle_IRQ+0x38/0x94) [] (handle_IRQ+0x38/0x94) from [] (gic_handle_irq+0x34/0x68) [] (gic_handle_irq+0x34/0x68) from [] (__irq_svc+0x40/0x70) Exception stack(0xc04cdf70 to 0xc04cdfb8) df60: 00000000 00000000 0000166e 00000000 df80: c04cc000 c050278f c050278f 00000001 c04d444c 410fc0f4 c03649b0 00000000 dfa0: 00000001 c04cdfb8 c000f758 c000f75c 60070013 ffffffff [] (__irq_svc+0x40/0x70) from [] (arch_cpu_idle+0x28/0x30) [] (arch_cpu_idle+0x28/0x30) from [] (cpu_startup_entry+0x5c/0x148) [] (cpu_startup_entry+0x5c/0x148) from [] (start_kernel+0x334/0x38c) BUG: spinlock lockup suspected on CPU#0, kworker/0:1/360 lock: s3c24xx_serial_ports+0x1d8/0x370, .magic: dead4ead, .owner: /-1, .owner_cpu: -1 CPU: 0 PID: 360 Comm: kworker/0:1 Not tainted 3.11.0-rc6-next-20130819-00003-g75485f1 #2 Workqueue: events flush_to_ldisc [] (unwind_backtrace+0x0/0xf8) from [] (show_stack+0x10/0x14) [] (show_stack+0x10/0x14) from [] (dump_stack+0x6c/0xac) [] (dump_stack+0x6c/0xac) from [] (do_raw_spin_lock+0x100/0x17c) [] (do_raw_spin_lock+0x100/0x17c) from [] (_raw_spin_lock_irqsave+0x20/0x28) [] (_raw_spin_lock_irqsave+0x20/0x28) from [] (uart_start+0x18/0x34) [] (uart_start+0x18/0x34) from [] (__receive_buf+0x4b4/0x738) [] (__receive_buf+0x4b4/0x738) from [] (n_tty_receive_buf2+0x30/0x98) [] (n_tty_receive_buf2+0x30/0x98) from [] (flush_to_ldisc+0xec/0x138) [] (flush_to_ldisc+0xec/0x138) from [] (process_one_work+0xfc/0x348) [] (process_one_work+0xfc/0x348) from [] (worker_thread+0x138/0x37c) [] (worker_thread+0x138/0x37c) from [] (kthread+0xa4/0xb0) [] (kthread+0xa4/0xb0) from [] (ret_from_fork+0x14/0x3c) ----- Release the port lock before calling tty_flip_buffer_push() and reacquire it after the call. Similar stuff was already done for few other drivers in the past, like: commit 2389b272168ceec056ca1d8a870a97fa9c26e11a Author: Thomas Gleixner Date: Tue May 29 21:53:50 2007 +0100 [ARM] 4417/1: Serial: Fix AMBA drivers locking Cc: Tony Prisk Signed-off-by: Viresh Kumar --- drivers/tty/serial/vt8500_serial.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/tty/serial/vt8500_serial.c b/drivers/tty/serial/vt8500_serial.c index a90bf04..93b697a 100644 --- a/drivers/tty/serial/vt8500_serial.c +++ b/drivers/tty/serial/vt8500_serial.c @@ -170,7 +170,9 @@ static void handle_rx(struct uart_port *port) tty_insert_flip_char(tport, c, flag); } + spin_unlock(&port->lock); tty_flip_buffer_push(tport); + spin_lock(&port->lock); } static void handle_tx(struct uart_port *port)