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Wed, 14 Oct 2026 08:24:42 -0700 (PDT) From: Joonho Lee To: Takashi Iwai Cc: Takashi Iwai , Jaroslav Kysela , linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Subject: [RFC PATCH v3 2/2] ALSA: pcm: refresh capture pointers in the drain action Date: Thu, 15 Oct 2026 00:24:39 +0900 Message-ID: In-Reply-To: References: <8733u8g0kh.wl-tiwai@suse.de> <87y0c0el29.wl-tiwai@suse.de> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Capture drain decides whether to retain unread data from the cached hardware pointer. A final subperiod can be omitted if the driver has advanced without a period notification or another pointer query. Refresh each running capture pointer in snd_pcm_do_drain_init(), with the normal drain action holding the stream and linked-group locks. Allow pointer accounting to return an error without issuing a nested XRUN or drain-complete action. Guard both the driver XRUN sentinel and the stop-threshold path; otherwise a linked drain can recursively enter the group stop action while its member locks are held. Let drain init own the stop: an update error ends that member in SETUP, while a successful update retains available capture frames in DRAINING. Ordinary pointer queries and period notifications retain their existing XRUN and drain-completion actions. Suggested-by: Takashi Iwai Link: https://lore.kernel.org/all/8733u8g0kh.wl-tiwai@suse.de/ Link: https://lore.kernel.org/all/87y0c0el29.wl-tiwai@suse.de/ Assisted-by: LLM Signed-off-by: Joonho Lee --- sound/core/pcm_lib.c | 34 ++++++++++++++++++++++++---------- sound/core/pcm_local.h | 2 ++ sound/core/pcm_native.c | 10 ++++++++-- 3 files changed, 34 insertions(+), 12 deletions(-) diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index de952f639d3b..2bb24d7dd2a1 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -206,8 +206,9 @@ void __snd_pcm_xrun(struct snd_pcm_substream *substream) #endif -int snd_pcm_update_state(struct snd_pcm_substream *substream, - struct snd_pcm_runtime *runtime) +static int do_pcm_update_state(struct snd_pcm_substream *substream, + struct snd_pcm_runtime *runtime, + bool notify) { snd_pcm_uframes_t avail; @@ -216,12 +217,14 @@ int snd_pcm_update_state(struct snd_pcm_substream *substream, runtime->avail_max = avail; if (runtime->state == SNDRV_PCM_STATE_DRAINING) { if (avail >= runtime->buffer_size) { - snd_pcm_drain_done(substream); + if (notify) + snd_pcm_drain_done(substream); return -EPIPE; } } else { if (avail >= runtime->stop_threshold) { - __snd_pcm_xrun(substream); + if (notify) + __snd_pcm_xrun(substream); return -EPIPE; } } @@ -233,6 +236,12 @@ int snd_pcm_update_state(struct snd_pcm_substream *substream, return 0; } +int snd_pcm_update_state(struct snd_pcm_substream *substream, + struct snd_pcm_runtime *runtime) +{ + return do_pcm_update_state(substream, runtime, true); +} + static void update_audio_tstamp(struct snd_pcm_substream *substream, struct timespec64 *curr_tstamp, struct timespec64 *audio_tstamp) @@ -283,8 +292,12 @@ static void update_audio_tstamp(struct snd_pcm_substream *substream, runtime->driver_tstamp = driver_tstamp; } -static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, - unsigned int in_interrupt) +/* + * Call with the stream lock held. With notify=false the caller handles + * stopping the stream, so pointer errors must not start a nested action. + */ +int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, + bool in_interrupt, bool notify) { struct snd_pcm_runtime *runtime = substream->runtime; snd_pcm_uframes_t pos; @@ -322,7 +335,8 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, } if (pos == SNDRV_PCM_POS_XRUN) { - __snd_pcm_xrun(substream); + if (notify) + __snd_pcm_xrun(substream); return -EPIPE; } if (pos >= runtime->buffer_size) { @@ -490,13 +504,13 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, update_audio_tstamp(substream, &curr_tstamp, &audio_tstamp); - return snd_pcm_update_state(substream, runtime); + return do_pcm_update_state(substream, runtime, notify); } /* CAUTION: call it with irq disabled */ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream) { - return snd_pcm_update_hw_ptr0(substream, 0); + return snd_pcm_update_hw_ptr0(substream, false, true); } /** @@ -1906,7 +1920,7 @@ void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substrea runtime = substream->runtime; if (!snd_pcm_running(substream) || - snd_pcm_update_hw_ptr0(substream, 1) < 0) + snd_pcm_update_hw_ptr0(substream, true, true) < 0) goto _end; #ifdef CONFIG_SND_PCM_TIMER diff --git a/sound/core/pcm_local.h b/sound/core/pcm_local.h index ecb21697ae3a..12bb6e75329a 100644 --- a/sound/core/pcm_local.h +++ b/sound/core/pcm_local.h @@ -28,6 +28,8 @@ int pcm_lib_apply_appl_ptr(struct snd_pcm_substream *substream, int snd_pcm_update_state(struct snd_pcm_substream *substream, struct snd_pcm_runtime *runtime); int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream); +int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, + bool in_interrupt, bool notify); void snd_pcm_playback_silence(struct snd_pcm_substream *substream, snd_pcm_uframes_t new_hw_ptr); diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index defbb2977efe..91ae46de3521 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -2094,6 +2094,8 @@ static int snd_pcm_do_drain_init(struct snd_pcm_substream *substream, snd_pcm_state_t state) { struct snd_pcm_runtime *runtime = substream->runtime; + int err; + if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) { switch (runtime->state) { case SNDRV_PCM_STATE_PREPARED: @@ -2119,8 +2121,12 @@ static int snd_pcm_do_drain_init(struct snd_pcm_substream *substream, if (runtime->state == SNDRV_PCM_STATE_RUNNING) { snd_pcm_state_t new_state; - new_state = snd_pcm_capture_avail(runtime) > 0 ? - SNDRV_PCM_STATE_DRAINING : SNDRV_PCM_STATE_SETUP; + err = snd_pcm_update_hw_ptr0(substream, false, false); + if (err < 0) + new_state = SNDRV_PCM_STATE_SETUP; + else + new_state = snd_pcm_capture_avail(runtime) > 0 ? + SNDRV_PCM_STATE_DRAINING : SNDRV_PCM_STATE_SETUP; snd_pcm_do_stop(substream, new_state); snd_pcm_post_stop(substream, new_state); } -- 2.54.0 (Apple Git-157)