Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755165Ab1DAJOj (ORCPT ); Fri, 1 Apr 2011 05:14:39 -0400 Received: from 216-146-103-100.dsl.nemontel.net ([216.146.103.100]:45135 "EHLO silka.with-linux.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753239Ab1DAJOh (ORCPT ); Fri, 1 Apr 2011 05:14:37 -0400 Message-ID: <4D959683.7040503@silka.with-linux.com> Date: Fri, 01 Apr 2011 03:10:27 -0600 From: Kelly Anderson User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110309 Thunderbird/3.1.9 MIME-Version: 1.0 To: Clemens Ladisch CC: "Christopher K." , Nix , linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org Subject: Re: Linux 2.6.38 freeze because of sound/core/pcm_lib.c commit 59ff878ffb26bc0be812ca8295799164f413ae88 References: <4D946C73.4090402@ladisch.de> <4D94F728.60609@silka.with-linux.com> <4D952B76.7000201@silka.with-linux.com> <4D95832F.3020200@ladisch.de> In-Reply-To: <4D95832F.3020200@ladisch.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2508 Lines: 61 On 04/01/11 01:47, Clemens Ladisch wrote: > > Kelly, to apply this patch I need a Signed-off-by tag from you (see > Documentation/SubmittingPatches). It works fine Clemens. --8<---------------------------------------------------------------->8-- ALSA: pcm: fix infinite loop in snd_pcm_update_hw_ptr0() When period interrupts are disabled, snd_pcm_update_hw_ptr0() compares the current time against the time estimated for the current hardware pointer to detect xruns. The somewhat fuzzy threshold in the while loop makes it possible that hdelta becomes negative; the comparison being done with unsigned types then makes the loop go through the entire 263 negative range, and, depending on the value, never reaching an unsigned value that is small enough to stop the loop. Doing this with interrupts disabled results in the machine locking up. To prevent this, ensure that the loop condition uses signed types for both operands so that the comparison is correctly done. Many thanks to Kelly Anderson for debugging this. Reported-by: Nix Reported-by: "Christopher K." Reported-by: Kelly Anderson [cl: remove unneeded casts; use a temp variable] Signed-off-by: Clemens Ladisch Signed-off-by: Kelly Anderson --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -375,6 +375,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, } if (runtime->no_period_wakeup) { + snd_pcm_sframes_t xrun_threshold; /* * Without regular period interrupts, we have to check * the elapsed time to detect xruns. @@ -383,7 +384,8 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, if (jdelta < runtime->hw_ptr_buffer_jiffies / 2) goto no_delta_check; hdelta = jdelta - delta * HZ / runtime->rate; + xrun_threshold = runtime->hw_ptr_buffer_jiffies / 2 + 1; - while (hdelta > runtime->hw_ptr_buffer_jiffies / 2 + 1) { + while (hdelta > xrun_threshold) { delta += runtime->buffer_size; hw_base += runtime->buffer_size; if (hw_base >= runtime->boundary) -- -- 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/