From: Arjan van de Ven <arjan@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: tiwai@suse.de, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sound: Fix race condition in the pcm_lib "wait for space loop
Date: Tue, 6 Sep 2011 20:07:36 -0700 [thread overview]
Message-ID: <20110906200736.785edef3@infradead.org> (raw)
In-Reply-To: <20110906155954.bb9c42eb.akpm@linux-foundation.org>
On Tue, 6 Sep 2011 15:59:54 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:
> > --- a/sound/core/pcm_lib.c
> > +++ b/sound/core/pcm_lib.c
> > @@ -1761,6 +1761,10 @@ static int wait_for_avail(struct
> > snd_pcm_substream *substream, snd_pcm_uframes_t avail = 0;
> > long wait_time, tout;
> >
> > + init_waitqueue_entry(&wait, current);
> > + add_wait_queue(&runtime->tsleep, &wait);
> > + set_current_state(TASK_INTERRUPTIBLE);
>
> Well, this isn't very good either. if a wakeup gets delivered to
> runtime->tsleep before the set_current_state(), this process will go
> ahead and incorrectly set itself into TASK_INTERRUPTIBLE state.
... and then check the condition for exit, and then set it to
TASK_RUNABLE a the end...
>
> That looks like it will be dont-care/cant-happen in this case, but
> it's setting a bad example.
agreed that your ordering is more clean/better.....
--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
WARNING: multiple messages have this Message-ID (diff)
From: Arjan van de Ven <arjan@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
perex@perex.cz, tiwai@suse.de
Subject: Re: [PATCH] sound: Fix race condition in the pcm_lib "wait for space loop
Date: Tue, 6 Sep 2011 20:07:36 -0700 [thread overview]
Message-ID: <20110906200736.785edef3@infradead.org> (raw)
In-Reply-To: <20110906155954.bb9c42eb.akpm@linux-foundation.org>
On Tue, 6 Sep 2011 15:59:54 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:
> > --- a/sound/core/pcm_lib.c
> > +++ b/sound/core/pcm_lib.c
> > @@ -1761,6 +1761,10 @@ static int wait_for_avail(struct
> > snd_pcm_substream *substream, snd_pcm_uframes_t avail = 0;
> > long wait_time, tout;
> >
> > + init_waitqueue_entry(&wait, current);
> > + add_wait_queue(&runtime->tsleep, &wait);
> > + set_current_state(TASK_INTERRUPTIBLE);
>
> Well, this isn't very good either. if a wakeup gets delivered to
> runtime->tsleep before the set_current_state(), this process will go
> ahead and incorrectly set itself into TASK_INTERRUPTIBLE state.
... and then check the condition for exit, and then set it to
TASK_RUNABLE a the end...
>
> That looks like it will be dont-care/cant-happen in this case, but
> it's setting a bad example.
agreed that your ordering is more clean/better.....
--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
next prev parent reply other threads:[~2011-09-07 3:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-05 16:49 [PATCH] sound: Fix race condition in the pcm_lib "wait for space loop Arjan van de Ven
2011-09-05 16:49 ` Arjan van de Ven
2011-09-06 22:59 ` Andrew Morton
2011-09-06 22:59 ` Andrew Morton
2011-09-07 3:07 ` Arjan van de Ven [this message]
2011-09-07 3:07 ` Arjan van de Ven
2011-09-12 9:57 ` [alsa-devel] " Takashi Iwai
2011-09-15 7:11 ` Takashi Iwai
2011-09-15 7:11 ` [alsa-devel] " Takashi Iwai
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