Commit 1ee23fe0 authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: usb-audio: Fix deadlocks at resuming 



The recent addition of the USB audio mixer suspend/resume may lead to
deadlocks when the driver tries to call usb_autopm_get_interface()
recursively, since the function tries to sync with the finish of the
other calls.  For avoiding it, introduce a flag indicating the resume
operation and avoids the recursive usb_autopm_get_interface() calls
during the resume.

Reported-and-tested-by: default avatarBryan Quigley <gquigs@gmail.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 1c53e725

sound/usb/card.c

+5 −2
Original line number Diff line number Diff line
@@ -651,7 +651,7 @@ int snd_usb_autoresume(struct snd_usb_audio *chip) 
	int err = -ENODEV;



	down_read(&chip->shutdown_rwsem);

	if (chip->probing)

	if (chip->probing && chip->in_pm)

		err = 0;

	else if (!chip->shutdown)

		err = usb_autopm_get_interface(chip->pm_intf);
@@ -663,7 +663,7 @@ int snd_usb_autoresume(struct snd_usb_audio *chip) 
void snd_usb_autosuspend(struct snd_usb_audio *chip)

{

	down_read(&chip->shutdown_rwsem);

	if (!chip->shutdown && !chip->probing)

	if (!chip->shutdown && !chip->probing && !chip->in_pm)

		usb_autopm_put_interface(chip->pm_intf);

	up_read(&chip->shutdown_rwsem);

}
@@ -712,6 +712,8 @@ static int __usb_audio_resume(struct usb_interface *intf, bool reset_resume) 
		return 0;

	if (--chip->num_suspended_intf)

		return 0;



	chip->in_pm = 1;

	/*

	 * ALSA leaves material resumption to user space

	 * we just notify and restart the mixers
@@ -727,6 +729,7 @@ static int __usb_audio_resume(struct usb_interface *intf, bool reset_resume) 
	chip->autosuspended = 0;



err_out:

	chip->in_pm = 0;

	return err;

}

sound/usb/usbaudio.h

+1 −0
Original line number Diff line number Diff line
@@ -40,6 +40,7 @@ struct snd_usb_audio { 
	struct rw_semaphore shutdown_rwsem;

	unsigned int shutdown:1;

	unsigned int probing:1;

	unsigned int in_pm:1;

	unsigned int autosuspended:1;	

	unsigned int txfr_quirk:1; /* Subframe boundaries on transfers */

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