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From: Sergei Shtylyov <sshtylyov-Igf4POYTYCDQT0dZR+AlfA@public.gmane.org>
To: Clemens Ladisch <clemens-P6GI/4k7KOmELgA04lAiVw@public.gmane.org>
Cc: Takashi Iwai <tiwai-l3A5Bk7waGM@public.gmane.org>,
	Sarah Sharp
	<sarah.a.sharp-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
	alsa-devel-K7yf7f+aM1XWsZ/bQMPhNw@public.gmane.org,
	linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	bossart.nospam-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	Alan Stern
	<stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org>,
	Pierre-Louis Bossart
	<pierre-louis.bossart-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: ALSA: usb-audio: fix oops due to cleanup race when disconnecting
Date: Tue, 22 Feb 2011 15:12:10 +0300	[thread overview]
Message-ID: <4D63A81A.5010002@ru.mvista.com> (raw)
In-Reply-To: <4D63800E.30509-P6GI/4k7KOmELgA04lAiVw@public.gmane.org>

Hello.

On 22-02-2011 12:21, Clemens Ladisch wrote:

> From: Takashi Iwai<tiwai-l3A5Bk7waGM@public.gmane.org>

> When a USB audio device is disconnected, snd_usb_audio_disconnect()
> kills all audio URBs.  At the same time, the application, after being
> notified of the disconnection, might close the device, in which case
> ALSA calls the .hw_free callback, which should free the URBs too.

> Commit de1b8b93a0ba prevented snd_usb_hw_free() from freeing the URBs to

    Linus asks to also specify the commit summary in parens.

> avoid a hang that resulted from this race, but this introduced another
> race because the URB callbacks could now be executed after
> snd_usb_hw_free() has returned, and try to access already freed data.

> Fix the first race by introducing a mutex to serialize the disconnect
> callback and all PCM callbacks that manage URBs (hw_free and hw_params).

> Reported-by: Pierre-Louis Bossart<pierre-louis.bossart-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> [CL: also serialize hw_params callback]
> Signed-off-by: Clemens Ladisch<clemens-P6GI/4k7KOmELgA04lAiVw@public.gmane.org>

WBR, Sergei
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      parent reply	other threads:[~2011-02-22 12:12 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-11 22:22 [PATCH] USB-sound: prevent kernel panic on disconnect Sarah Sharp
2011-02-11 22:42 ` Alan Stern
     [not found]   ` <Pine.LNX.4.44L0.1102111737280.13739-100000-pYrvlCTfrz9XsRXLowluHWD2FQJk+8+b@public.gmane.org>
2011-02-14  8:54     ` Clemens Ladisch
2011-02-14 17:39       ` Takashi Iwai
     [not found]         ` <s5hoc6ejz2j.wl%tiwai-l3A5Bk7waGM@public.gmane.org>
2011-02-16 23:54           ` Sarah Sharp
2011-02-17 13:52             ` Clemens Ladisch
2011-02-17 15:16             ` Takashi Iwai
     [not found]               ` <s5hk4gyy9m1.wl%tiwai-l3A5Bk7waGM@public.gmane.org>
2011-02-22  9:21                 ` ALSA: usb-audio: fix oops due to cleanup race when disconnecting Clemens Ladisch
     [not found]                   ` <4D63800E.30509-P6GI/4k7KOmELgA04lAiVw@public.gmane.org>
2011-02-22  9:37                     ` Takashi Iwai
     [not found]                       ` <s5hfwrg9zpv.wl%tiwai-l3A5Bk7waGM@public.gmane.org>
2011-02-22 20:18                         ` pl bossart
     [not found]                           ` <AANLkTikcXPTZYYwYDunq4pJwzDhxSv5u++jEWN0RU4EQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-02-22 21:38                             ` Sarah Sharp
2011-02-22 22:19                           ` pl bossart
     [not found]                             ` <AANLkTi=tYR1daV8zWschBikOkcOgWk864n+b-30q4sSD-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-02-22 23:54                               ` Takashi Iwai
2011-02-22 23:10                         ` pl bossart
     [not found]                           ` <AANLkTimNhi7GT4NbQRrNq6kyrKOQhudF2owf=U_qzQav-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-02-23  7:17                             ` Takashi Iwai
2011-02-22 12:12                     ` Sergei Shtylyov [this message]

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