linux-kernel - [PATCH V0 1/1] ALSA: pcm: fix blocking while loop in snd_pcm_update_hw

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Date:   Fri, 25 Feb 2022 16:09:32 +0530
From:   Raghu Bankapur <quic_rbankapu@...cinc.com>
To:     Vinod Koul <vkoul@...nel.org>, Jaroslav Kysela <perex@...ex.cz>,
        "Takashi Iwai" <tiwai@...e.com>,
        ierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        "Kai Vehmanen" <kai.vehmanen@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Takashi Sakamoto <o-takashi@...amocchi.jp>,
        Raghu Bankapur <quic_rbankapu@...cinc.com>,
        <alsa-devel@...a-project.org>, Zubin Mithra <zsm@...omium.org>,
        <linux-kernel@...r.kernel.org>
CC:     Krishna Jha <quic_kkishorj@...cinc.com>
Subject: [PATCH V0 1/1] ALSA: pcm: fix blocking while loop in snd_pcm_update_hw_ptr0()

When period interrupts are disabled, while loop in snd_pcm_update_hw_ptr0()
results in the machine locking up if runtime->hw_ptr_buffer_jiffies is 0.
Validate runtime->hw_ptr_buffer_jiffies value before while loop to avoid
delta check.

Signed-off-by: Raghu Bankapur <quic_rbankapu@...cinc.com>
---
 sound/core/pcm_lib.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index f2090025236b..bb9097f658be 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -352,7 +352,8 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
 		 * the elapsed time to detect xruns.
 		 */
 		jdelta = curr_jiffies - runtime->hw_ptr_jiffies;
-		if (jdelta < runtime->hw_ptr_buffer_jiffies / 2)
+		if ((jdelta < runtime->hw_ptr_buffer_jiffies / 2) ||
+			(runtime->hw_ptr_buffer_jiffies <= 0))
 			goto no_delta_check;
 		hdelta = jdelta - delta * HZ / runtime->rate;
 		xrun_threshold = runtime->hw_ptr_buffer_jiffies / 2 + 1;
-- 
2.17.1