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[ALSA] race between disconnect and error handling in usbmidi

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The driver resubmits URBs from an error handler and schedules the error
handler from the URBs' completion handlers. To reliably kill the cycle
a flag must be used.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Takashi Iwai 2008-02-22 18:34:44 +01:00 committed by Linus Torvalds
parent 0ee46c9dad
commit c0792e00bc
1 changed files with 18 additions and 1 deletions
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19
sound/usb/usbmidi.c
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@ -104,12 +104,14 @@ struct snd_usb_midi {
struct usb_protocol_ops* usb_protocol_ops;
struct list_head list;
struct timer_list error_timer;
spinlock_t disc_lock;
struct snd_usb_midi_endpoint {
struct snd_usb_midi_out_endpoint *out;
struct snd_usb_midi_in_endpoint *in;
} endpoints[MIDI_MAX_ENDPOINTS];
unsigned long input_triggered;
unsigned char disconnected;
};
struct snd_usb_midi_out_endpoint {
@ -306,6 +308,11 @@ static void snd_usbmidi_error_timer(unsigned long data)
struct snd_usb_midi *umidi = (struct snd_usb_midi *)data;
int i;
spin_lock(&umidi->disc_lock);
if (umidi->disconnected) {
spin_unlock(&umidi->disc_lock);
return;
}
for (i = 0; i < MIDI_MAX_ENDPOINTS; ++i) {
struct snd_usb_midi_in_endpoint *in = umidi->endpoints[i].in;
if (in && in->error_resubmit) {
@ -316,6 +323,7 @@ static void snd_usbmidi_error_timer(unsigned long data)
if (umidi->endpoints[i].out)
snd_usbmidi_do_output(umidi->endpoints[i].out);
}
spin_unlock(&umidi->disc_lock);
}
/* helper function to send static data that may not DMA-able */
@ -1049,7 +1057,14 @@ void snd_usbmidi_disconnect(struct list_head* p)
int i;
umidi = list_entry(p, struct snd_usb_midi, list);
del_timer_sync(&umidi->error_timer);
/*
* an URB's completion handler may start the timer and
* a timer may submit an URB. To reliably break the cycle
* a flag under lock must be used
*/
spin_lock_irq(&umidi->disc_lock);
umidi->disconnected = 1;
spin_unlock_irq(&umidi->disc_lock);
for (i = 0; i < MIDI_MAX_ENDPOINTS; ++i) {
struct snd_usb_midi_endpoint* ep = &umidi->endpoints[i];
if (ep->out)
@ -1062,6 +1077,7 @@ void snd_usbmidi_disconnect(struct list_head* p)
if (ep->in)
usb_kill_urb(ep->in->urb);
}
del_timer_sync(&umidi->error_timer);
}
static void snd_usbmidi_rawmidi_free(struct snd_rawmidi *rmidi)
@ -1685,6 +1701,7 @@ int snd_usb_create_midi_interface(struct snd_usb_audio* chip,
umidi->quirk = quirk;
umidi->usb_protocol_ops = &snd_usbmidi_standard_ops;
init_timer(&umidi->error_timer);
spin_lock_init(&umidi->disc_lock);
umidi->error_timer.function = snd_usbmidi_error_timer;
umidi->error_timer.data = (unsigned long)umidi;