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From: Takashi Iwai <tiwai@suse.de>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	bugme-daemon@bugzilla.kernel.org, linux-kernel@vger.kernel.org,
	Ingo Molnar <mingo@elte.hu>, Stas Sergeev <stsp@aknet.ru>
Subject: Re: [Bugme-new] [Bug 10701] New: snd_pcsp lockdep warning
Date: Sat, 17 May 2008 15:45:57 +0200	[thread overview]
Message-ID: <s5hwsltm4bu.wl%tiwai@suse.de> (raw)
In-Reply-To: <alpine.LFD.1.10.0805162132050.3255@apollo.tec.linutronix.de>

At Fri, 16 May 2008 21:32:49 +0200 (CEST),
Thomas Gleixner wrote:
> 
> On Fri, 16 May 2008, Andrew Morton wrote:
> > > So the author was well aware of locking problem and the whole code is
> > > just a stupid hack around the problem without solving it. This code is
> > > not at all suited for HRTIMER_CB_IRQSAFE.
> > 
> > You sound impressed!  So what's the fix?  HRTIMER_CB_SOFTIRQ?
> 
> Yeah, impressed by creativity. HRTIMER_CB_SOFTIRQ should be the right
> thing.

Well, it'd be basically a similar way like snd-pcsp currently does ("a
stupid hack" :)  But, it's good to have a fix, anyway, since this
sounds like a generic problem with a callback in a spinlock.  If the
callback requires another own lock, this can easily lead to a AB/BA
deadlock.  Actually, ALSA PCM core had sometimes similar problems,
too.


thanks,

Takashi

  reply	other threads:[~2008-05-17 13:46 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <bug-10701-10286@http.bugzilla.kernel.org/>
2008-05-15 18:02 ` Andrew Morton
2008-05-16 12:46   ` Thomas Gleixner
2008-05-16 17:38     ` Andrew Morton
2008-05-16 19:32       ` Thomas Gleixner
2008-05-17 13:45         ` Takashi Iwai [this message]
2008-05-17 15:24           ` Thomas Gleixner
2008-05-18  7:55             ` Takashi Iwai

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