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Thu, 10 Jun 2021 10:08:47 +0200 (CEST) Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 45E54F80149 for ; Thu, 10 Jun 2021 10:08:39 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 45E54F80149 Authentication-Results: alsa1.perex.cz; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="eFMYMV+2"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="ku/BGiBP" Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id A1FA61FD37; Thu, 10 Jun 2021 08:08:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1623312519; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; 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charset=US-ASCII Cc: alsa-devel@alsa-project.org, clemens@ladisch.de X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Thu, 10 Jun 2021 10:05:21 +0200, Takashi Sakamoto wrote: > > On Thu, Jun 10, 2021 at 09:39:37AM +0200, Takashi Iwai wrote: > > On Thu, 10 Jun 2021 01:16:23 +0200, > > Takashi Sakamoto wrote: > > > > > > On Wed, Jun 09, 2021 at 05:27:29PM +0200, Takashi Iwai wrote: > > > > On Wed, 09 Jun 2021 16:31:43 +0200, > > > > Takashi Sakamoto wrote: > > > > > diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c > > > > > index b7e3d8f44511..3488ec1e3674 100644 > > > > > --- a/sound/core/pcm_lib.c > > > > > +++ b/sound/core/pcm_lib.c > > > > > @@ -1778,27 +1778,41 @@ int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream, > > > > > EXPORT_SYMBOL(snd_pcm_lib_ioctl); > > > > > > > > > > /** > > > > > - * snd_pcm_period_elapsed - update the pcm status for the next period > > > > > - * @substream: the pcm substream instance > > > > > + * snd_pcm_period_elapsed_under_stream_lock() - update the status of runtime for the next period > > > > > + * under acquired lock of PCM substream. > > > > > + * @substream: the instance of pcm substream. > > > > > + * > > > > > + * This function is called when the batch of audio data frames as the same size as the period of > > > > > + * buffer is already processed in audio data transmission. > > > > > + * > > > > > + * The call of function updates the status of runtime with the latest position of audio data > > > > > + * transmission, checks overrun and underrun over buffer, awaken user processes from waiting for > > > > > + * available audio data frames, sampling audio timestamp, and performs stop or drain the PCM > > > > > + * substream according to configured threshold. > > > > > + * > > > > > + * The function is intended to use for the case that PCM driver operates audio data frames under > > > > > + * acquired lock of PCM substream; e.g. in callback of any operation of &snd_pcm_ops in process > > > > > + * context. In any interrupt context, it's preferrable to use ``snd_pcm_period_elapsed()`` instead > > > > > + * since lock of PCM substream should be acquired in advance. > > > > > * > > > > > - * This function is called from the interrupt handler when the > > > > > - * PCM has processed the period size. It will update the current > > > > > - * pointer, wake up sleepers, etc. > > > > > + * Developer should pay enough attention that some callbacks in &snd_pcm_ops are done by the call of > > > > > + * function: > > > > > * > > > > > - * Even if more than one periods have elapsed since the last call, you > > > > > - * have to call this only once. > > > > > + * - .pointer - to retrieve current position of audio data transmission by frame count or XRUN state. > > > > > + * - .trigger - with SNDRV_PCM_TRIGGER_STOP at XRUN or DRAINING state. > > > > > + * - .get_time_info - to retrieve audio time stamp if needed. > > > > > + * > > > > > + * Even if more than one periods have elapsed since the last call, you have to call this only once. > > > > > + * > > > > > + * Context: Any context in which lock of PCM substream is already acquired. This function may not > > > > > + * sleep. > > > > > > > > Hm, this text still remains here. Overlooked? > > > > > > It's my intension for documentation of > > > snd_pcm_period_elapsed_under_stream_lock() since it's expected to call > > > it under acquired lock. Its implementation doesn't yield processor > > > voluntarily by itself. If it yielded, it would depend on implementation > > > of each driver for struct snd_pcm_ops.{pointer, trigger, get_time_info}, > > > but it's not preferable implementation of driver, in my opinion. > > > > My point is again about the sleep. This function may sleep in the > > nonatomic mode. The type of the PCM stream lock depends on it. > > Would I simply request you to show how the added function yields except > for the driver implementation? The lock of stream is expected to be > acquired already. In the nonatomic mode, the PCM stream lock is a mutex (no spin_lock_irqsave), hence it can sleep -- which contradicts with the added description above. Or do I misunderstand your question...? Takashi