Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751530AbaJAMBg (ORCPT ); Wed, 1 Oct 2014 08:01:36 -0400 Received: from bear.ext.ti.com ([192.94.94.41]:51261 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751053AbaJAMBd (ORCPT ); Wed, 1 Oct 2014 08:01:33 -0400 Message-ID: <542BECF5.2090700@ti.com> Date: Wed, 1 Oct 2014 15:00:53 +0300 From: Peter Ujfalusi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: Sebastian Andrzej Siewior , CC: , , , , , , Subject: Re: [PATCH 09/13] dmaengine: edma: check for echan->edesc => NULL in edma_dma_pause() References: <1412014009-13315-1-git-send-email-bigeasy@linutronix.de> <1412014009-13315-10-git-send-email-bigeasy@linutronix.de> In-Reply-To: <1412014009-13315-10-git-send-email-bigeasy@linutronix.de> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/29/2014 09:06 PM, Sebastian Andrzej Siewior wrote: > 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. Acked-by: Peter Ujfalusi > > Cc: vinod.koul@intel.com > Signed-off-by: Sebastian Andrzej Siewior > --- > 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); > -- P?ter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/