From mboxrd@z Thu Jan 1 00:00:00 1970 From: pl bossart Subject: Re: Duplicate wake-ups in pcm_lib.c Date: Mon, 11 Jan 2010 14:46:33 -0600 Message-ID: <6160a5131001111246m48448cedrfa83f9ae39cd6403@mail.gmail.com> References: <6160a5130912231228g29669e4ctfef9ea8f42633120@mail.gmail.com> <6160a5131001062059i1ef74831p4210987579feb759@mail.gmail.com> <6160a5131001111036v355685c9j89e85cd13e82e3dc@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pz0-f184.google.com (mail-pz0-f184.google.com [209.85.222.184]) by alsa0.perex.cz (Postfix) with ESMTP id EDB68244EC for ; Mon, 11 Jan 2010 21:46:34 +0100 (CET) Received: by pzk14 with SMTP id 14so2031267pzk.23 for ; Mon, 11 Jan 2010 12:46:33 -0800 (PST) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Jaroslav Kysela Cc: ALSA development , Lennart Poettering List-Id: alsa-devel@alsa-project.org >> I couldn't figure out who generates this null event, and even better >> it does not show in the report printed by my test app. I am somewhat >> lost here as to how snd_pcm_playback_poll works. > > Note that do_poll() in linux/fs/select.c first checks all given fds > if there's an event. So probably the userspace just called poll() for a > reason in different timing than sound one (processing event from another fd > or so). I believe it's normal behaviour. This was tested with alsa-lib/test/pcm.c; there's only one call to poll() with a -1 timeout value. What I fail to understand is why I see this null event in pcm_native.c, and nothing reported in userspace by the wait_for_poll() loop in alsa-lib/test/pcm.c