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: 4998211 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 09A629F348 for ; Mon, 29 Sep 2014 18:09:42 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 371BE201C0 for ; Mon, 29 Sep 2014 18:09:41 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 477202011E for ; Mon, 29 Sep 2014 18:09:40 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1XYfMC-00071z-0R; Mon, 29 Sep 2014 18:07:32 +0000 Received: from galois.linutronix.de ([2001:470:1f0b:db:abcd:42:0:1]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1XYfM0-0006qo-0D for linux-arm-kernel@lists.infradead.org; Mon, 29 Sep 2014 18:07:21 +0000 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 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20140929_110720_235893_32431256 X-CRM114-Status: GOOD ( 12.43 ) X-Spam-Score: -0.8 (/) Cc: tony@atomide.com, gregkh@linuxfoundation.org, Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, balbi@ti.com, vinod.koul@intel.com, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_NONE, 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);