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From:   Raghu Bankapur <quic_rbankapu@quicinc.com>
To:     Vinod Koul <vkoul@kernel.org>, Jaroslav Kysela <perex@perex.cz>,
        "Takashi Iwai" <tiwai@suse.com>,
        ierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
        Mark Brown <broonie@kernel.org>,
        "Kai Vehmanen" <kai.vehmanen@linux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@linux.intel.com>,
        Takashi Sakamoto <o-takashi@sakamocchi.jp>,
        Raghu Bankapur <quic_rbankapu@quicinc.com>,
        <alsa-devel@alsa-project.org>, Zubin Mithra <zsm@chromium.org>,
        <linux-kernel@vger.kernel.org>
CC:     Krishna Jha <quic_kkishorj@quicinc.com>
Subject: [PATCH V0 0/1] ALSA: pcm: fix blocking while loop in 
Date:   Fri, 25 Feb 2022 16:09:31 +0530
Message-ID: <cover.1645784757.git.quic_rbankapu@quicinc.com>
MIME-Version: 1.0
Content-Type: text/plain
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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.


when runtime->hw_ptr_buffer_jiffies is 0 then update of while condition 
hdelta > xrun_threshold will be always true because hdelta will not
change. This will lead to infinite loop causing lock-up

This issue found during stability test, below log explains CPU lock-up on CPU1

[ 922.249028] sched: RT throttling activated for rt_rq ffffffc0f9970778 (cpu 1)
[ 922.249028] potential CPU hogs:
[ 922.249028] **FastCapture (11426)
[ 922.249105] ------------[ cut here ]---------

To fix this lock-up issue, added new condition to check if runtime->
hw_ptr_buffer_jiffies is ZERO or negative.

Raghu Bankapur (1):
  ALSA: pcm: fix blocking while loop in snd_pcm_update_hw_ptr0()

 sound/core/pcm_lib.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

-- 
2.17.1