From patchwork Fri Aug 28 03:13:09 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shawn Lin X-Patchwork-Id: 7089351 Return-Path: X-Original-To: patchwork-linux-mmc@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 7445EBEEC1 for ; Fri, 28 Aug 2015 03:14:23 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 010F52099E for ; Fri, 28 Aug 2015 03:14:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D83CB2097B for ; Fri, 28 Aug 2015 03:14:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751074AbbH1DOS (ORCPT ); Thu, 27 Aug 2015 23:14:18 -0400 Received: from lucky1.263xmail.com ([211.157.147.132]:34801 "EHLO lucky1.263xmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751014AbbH1DOR (ORCPT ); Thu, 27 Aug 2015 23:14:17 -0400 Received: from shawn.lin?rock-chips.com (unknown [192.168.167.157]) by lucky1.263xmail.com (Postfix) with SMTP id 18EB3586F5; Fri, 28 Aug 2015 11:14:11 +0800 (CST) X-263anti-spam: KSV:0;BIG:0;ABS:1;DNS:0;ATT:0;SPF:S; X-MAIL-GRAY: 1 X-MAIL-DELIVERY: 0 X-KSVirus-check: 0 X-ABS-CHECKED: 1 X-SKE-CHECKED: 1 X-ADDR-CHECKED: 0 Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.263.net (Postfix) with ESMTP id 1EC6D1BAE9; Fri, 28 Aug 2015 11:14:07 +0800 (CST) X-RL-SENDER: shawn.lin@rock-chips.com X-FST-TO: ulf.hansson@linaro.org X-SENDER-IP: 58.22.7.114 X-LOGIN-NAME: shawn.lin@rock-chips.com X-UNIQUE-TAG: X-ATTACHMENT-NUM: 0 X-SENDER: lintao@rock-chips.com X-DNS-TYPE: 0 Received: from localhost.localdomain (unknown [58.22.7.114]) by smtp.263.net (Postfix) whith ESMTP id 178137JXN3X; Fri, 28 Aug 2015 11:14:08 +0800 (CST) From: Shawn Lin To: Ulf Hansson Cc: Jialing Fu , linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RESEND PATCH] mmc: core: fix race condition in mmc_wait_data_done Date: Fri, 28 Aug 2015 11:13:09 +0800 Message-Id: <1440731589-22241-1-git-send-email-shawn.lin@rock-chips.com> X-Mailer: git-send-email 1.8.0 Sender: linux-mmc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mmc@vger.kernel.org X-Spam-Status: No, score=-6.6 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY, URIBL_BLACK autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Jialing Fu The following panic is captured in ker3.14, but the issue still exists in latest kernel. --------------------------------------------------------------------- [ 20.738217] c0 3136 (Compiler) Unable to handle kernel NULL pointer dereference at virtual address 00000578 ...... [ 20.738499] c0 3136 (Compiler) PC is at _raw_spin_lock_irqsave+0x24/0x60 [ 20.738527] c0 3136 (Compiler) LR is at _raw_spin_lock_irqsave+0x20/0x60 [ 20.740134] c0 3136 (Compiler) Call trace: [ 20.740165] c0 3136 (Compiler) [] _raw_spin_lock_irqsave+0x24/0x60 [ 20.740200] c0 3136 (Compiler) [] __wake_up+0x1c/0x54 [ 20.740230] c0 3136 (Compiler) [] mmc_wait_data_done+0x28/0x34 [ 20.740262] c0 3136 (Compiler) [] mmc_request_done+0xa4/0x220 [ 20.740314] c0 3136 (Compiler) [] sdhci_tasklet_finish+0xac/0x264 [ 20.740352] c0 3136 (Compiler) [] tasklet_action+0xa0/0x158 [ 20.740382] c0 3136 (Compiler) [] __do_softirq+0x10c/0x2e4 [ 20.740411] c0 3136 (Compiler) [] irq_exit+0x8c/0xc0 [ 20.740439] c0 3136 (Compiler) [] handle_IRQ+0x48/0xac [ 20.740469] c0 3136 (Compiler) [] gic_handle_irq+0x38/0x7c ---------------------------------------------------------------------- Because in SMP, "mrq" has race condition between below two paths: path1: CPU0: static void mmc_wait_data_done(struct mmc_request *mrq) { mrq->host->context_info.is_done_rcv = true; // // If CPU0 has just finished "is_done_rcv = true" in path1, and at // this moment, IRQ or ICache line missing happens in CPU0. // What happens in CPU1 (path2)? // // If the mmcqd thread in CPU1(path2) hasn't entered to sleep mode: // path2 would have chance to break from wait_event_interruptible // in mmc_wait_for_data_req_done and continue to run for next // mmc_request (mmc_blk_rw_rq_prep). // // Within mmc_blk_rq_prep, mrq is cleared to 0. // If below line still gets host from "mrq" as the result of // compiler, the panic happens as we traced. wake_up_interruptible(&mrq->host->context_info.wait); } path2: CPU1: static int mmc_wait_for_data_req_done(... { ... while (1) { wait_event_interruptible(context_info->wait, (context_info->is_done_rcv || context_info->is_new_req)); static void mmc_blk_rw_rq_prep(... { ... memset(brq, 0, sizeof(struct mmc_blk_request)); This issue happens very coincidentally; however adding mdelay(1) in mmc_wait_data_done as below could duplicate it easily. static void mmc_wait_data_done(struct mmc_request *mrq) { mrq->host->context_info.is_done_rcv = true; + mdelay(1); wake_up_interruptible(&mrq->host->context_info.wait); } At runtime, IRQ or ICache line missing may just happen at the same place of the mdelay(1). This patch gets the mmc_context_info at the beginning of function, it can avoid this race condition. Signed-off-by: Jialing Fu Tested-by: Shawn Lin --- drivers/mmc/core/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index 664b617..0520064 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -358,8 +358,10 @@ EXPORT_SYMBOL(mmc_start_bkops); */ static void mmc_wait_data_done(struct mmc_request *mrq) { - mrq->host->context_info.is_done_rcv = true; - wake_up_interruptible(&mrq->host->context_info.wait); + struct mmc_context_info *context_info = &mrq->host->context_info; + + context_info->is_done_rcv = true; + wake_up_interruptible(&context_info->wait); } static void mmc_wait_done(struct mmc_request *mrq)