Commit 8653d71c authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Greg Kroah-Hartman
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usb/gadget: f_midi: Replace tasklet with work 



Currently a tasklet is used to transmit input substream buffer
data. However, tasklets have long been deprecated as being too
heavy on the system by running in irq context - and this is not
a performance critical path. If a higher priority process wants
to run, it must wait for the tasklet to finish before doing so.

Deferring work to a workqueue and executing in process context
should be fine considering the callback already does
f_midi_do_transmit() under the transmit_lock and thus changes in
semantics are ok regarding concurrency - tasklets being serialized
against itself.

Cc: Takashi Iwai <tiwai@suse.de>
Reviewed-by: default avatarTakashi Iwai <tiwai@suse.de>
Acked-by: default avatarFelipe Balbi <balbi@kernel.org>
Signed-off-by: default avatarDavidlohr Bueso <dbueso@suse.de>
Link: https://lore.kernel.org/r/20210111042855.73289-1-dave@stgolabs.net


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 0c0a20f6

drivers/usb/gadget/function/f_midi.c

+7 −5
Original line number Diff line number Diff line
@@ -87,7 +87,7 @@ struct f_midi { 
	struct snd_rawmidi_substream *out_substream[MAX_PORTS];



	unsigned long		out_triggered;

	struct tasklet_struct	tasklet;

	struct work_struct	work;

	unsigned int in_ports;

	unsigned int out_ports;

	int index;
@@ -698,9 +698,11 @@ static void f_midi_transmit(struct f_midi *midi) 
	f_midi_drop_out_substreams(midi);

}



static void f_midi_in_tasklet(struct tasklet_struct *t)

static void f_midi_in_work(struct work_struct *work)

{

	struct f_midi *midi = from_tasklet(midi, t, tasklet);

	struct f_midi *midi;



	midi = container_of(work, struct f_midi, work);

	f_midi_transmit(midi);

}
@@ -737,7 +739,7 @@ static void f_midi_in_trigger(struct snd_rawmidi_substream *substream, int up) 
	VDBG(midi, "%s() %d\n", __func__, up);

	midi->in_ports_array[substream->number].active = up;

	if (up)

		tasklet_hi_schedule(&midi->tasklet);

		queue_work(system_highpri_wq, &midi->work);

}



static int f_midi_out_open(struct snd_rawmidi_substream *substream)
@@ -875,7 +877,7 @@ static int f_midi_bind(struct usb_configuration *c, struct usb_function *f) 
	int status, n, jack = 1, i = 0, endpoint_descriptor_index = 0;



	midi->gadget = cdev->gadget;

	tasklet_setup(&midi->tasklet, f_midi_in_tasklet);

	INIT_WORK(&midi->work, f_midi_in_work);

	status = f_midi_register_card(midi);

	if (status < 0)

		goto fail_register;