From patchwork Mon Sep 29 18:06:45 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 4998191 Return-Path: X-Original-To: patchwork-linux-omap@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 18556BEEA6 for ; Mon, 29 Sep 2014 18:09:18 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 40CF4201C7 for ; Mon, 29 Sep 2014 18:09:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6DA8B201BC for ; Mon, 29 Sep 2014 18:09:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755192AbaI2SIU (ORCPT ); Mon, 29 Sep 2014 14:08:20 -0400 Received: from www.linutronix.de ([62.245.132.108]:53258 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755040AbaI2SHB (ORCPT ); Mon, 29 Sep 2014 14:07:01 -0400 Received: from localhost ([127.0.0.1] helo=bazinga.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1XYfLf-0001xV-N1; Mon, 29 Sep 2014 20:06:59 +0200 From: Sebastian Andrzej Siewior To: linux-serial@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, tony@atomide.com, balbi@ti.com, gregkh@linuxfoundation.org, Sebastian Andrzej Siewior , vinod.koul@intel.com Subject: [PATCH 09/13] dmaengine: edma: check for echan->edesc => NULL in edma_dma_pause() Date: Mon, 29 Sep 2014 20:06:45 +0200 Message-Id: <1412014009-13315-10-git-send-email-bigeasy@linutronix.de> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1412014009-13315-1-git-send-email-bigeasy@linutronix.de> References: <1412014009-13315-1-git-send-email-bigeasy@linutronix.de> X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1, SHORTCIRCUIT=-0.0001, URIBL_BLOCKED=0.001 Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org X-Spam-Status: No, score=-7.7 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable 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 I added book keeping of whether or not the 8250-dma driver has an RX transfer pending or not so we don't BUG here if it calls dmaengine_pause() on a channel which has not a pending transfer. Guess what, this is not enough. The following can be triggered with a busy RX channel and hackbench in background: - DMA transfer completes. The callback is delayed via vchan_cookie_complete() into a tasklet so it das not happen asap. - hackbench keeps the system busy so the tasklet does not run "soon". - the UART collected enough data and generates an "timeout"-interrupt. Since 8250-dma *thinks* the DMA-transfer is still pending it tries to cancel it via invoking dmaengine_pause() first. This causes the segfault because echan->edesc is NULL now that the transfer completed (however the callback did not run yet). With this patch we don't BUG in the scenario described. Cc: vinod.koul@intel.com Signed-off-by: Sebastian Andrzej Siewior Acked-by: Peter Ujfalusi --- drivers/dma/edma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c index 7b65633f495e..123f578d6dd3 100644 --- a/drivers/dma/edma.c +++ b/drivers/dma/edma.c @@ -288,7 +288,7 @@ static int edma_slave_config(struct edma_chan *echan, static int edma_dma_pause(struct edma_chan *echan) { /* Pause/Resume only allowed with cyclic mode */ - if (!echan->edesc->cyclic) + if (!echan->edesc || !echan->edesc->cyclic) return -EINVAL; edma_pause(echan->ch_num);