ALSA: seq: Clean up fifo locking with guard

Yet more cleanup, now for seq_fifo.c about its refcount calls; the
manual refcount calls (either snd_use_lock_*() or snd_seq_fifo_lock())
are replaced with guard(snd_seq_fifo).

Only code refactoring, and no behavior change.

Signed-off-by: Takashi Iwai <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

sound/core/seq/seq_clientmgr.c

···
 
 	cell = NULL;
 	err = 0;
-	snd_seq_fifo_lock(fifo);
+	guard(snd_seq_fifo)(fifo);
 
 	if (IS_ENABLED(CONFIG_SND_SEQ_UMP) && client->midi_version > 0)
 		aligned_size = sizeof(struct snd_seq_ump_event);
···
 		if (err == -EAGAIN && result > 0)
 			err = 0;
 	}
-	snd_seq_fifo_unlock(fifo);
 
 	return (err < 0) ? err : result;
 }

sound/core/seq/seq_fifo.c

···
 	if (snd_BUG_ON(!f))
 		return -EINVAL;
 
-	snd_use_lock_use(&f->use_lock);
+	guard(snd_seq_fifo)(f);
 	err = snd_seq_event_dup(f->pool, event, &cell, 1, NULL, NULL); /* always non-blocking */
 	if (err < 0) {
 		if ((err == -ENOMEM) || (err == -EAGAIN))
 			atomic_inc(&f->overflow);
-		snd_use_lock_free(&f->use_lock);
 		return err;
 	}
 		
···
 	/* wakeup client */
 	if (waitqueue_active(&f->input_sleep))
 		wake_up(&f->input_sleep);
-
-	snd_use_lock_free(&f->use_lock);
 
 	return 0; /* success */
 
···
 /* get the number of unused cells safely */
 int snd_seq_fifo_unused_cells(struct snd_seq_fifo *f)
 {
-	int cells;
-
 	if (!f)
 		return 0;
 
-	snd_use_lock_use(&f->use_lock);
-	scoped_guard(spinlock_irqsave, &f->lock)
-		cells = snd_seq_unused_cells(f->pool);
-	snd_use_lock_free(&f->use_lock);
-	return cells;
+	guard(snd_seq_fifo)(f);
+	guard(spinlock_irqsave)(&f->lock);
+	return snd_seq_unused_cells(f->pool);
 }

sound/core/seq/seq_fifo.h

···
 /* lock fifo from release */
 #define snd_seq_fifo_lock(fifo)		snd_use_lock_use(&(fifo)->use_lock)
 #define snd_seq_fifo_unlock(fifo)	snd_use_lock_free(&(fifo)->use_lock)
+DEFINE_GUARD(snd_seq_fifo, struct snd_seq_fifo *, snd_seq_fifo_lock(_T), snd_seq_fifo_unlock(_T))
 
 /* get a cell from fifo - fifo should be locked */
 int snd_seq_fifo_cell_out(struct snd_seq_fifo *f, struct snd_seq_event_cell **cellp, int nonblock);