ALSA: usx2y: Fix shmem initialization

Currently us428ctls_shmem pages are allocated dynamically upon the
mmap call, but this is quite racy.  Since the shared memory itself is
mandatory for the mmap, let's allocate it at the beginning of the card
initialization.  Also, fix the initialization of the wait queue, too.

Link: https://lore.kernel.org/r/20210517131545.27252-9-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/usx2y/usX2Yhwdep.c

@@ -60,14 +60,6 @@ static int snd_us428ctls_mmap(struct snd_hwdep *hw, struct file *filp, struct vm
 		return -EINVAL;
 	}
 
-	if (!us428->us428ctls_sharedmem) {
-		init_waitqueue_head(&us428->us428ctls_wait_queue_head);
-		us428->us428ctls_sharedmem = alloc_pages_exact(US428_SHAREDMEM_PAGES, GFP_KERNEL);
-		if (!us428->us428ctls_sharedmem)
-			return -ENOMEM;
-		memset(us428->us428ctls_sharedmem, -1, US428_SHAREDMEM_PAGES);
-		us428->us428ctls_sharedmem->ctl_snapshot_last = -2;
-	}
 	area->vm_ops = &us428ctls_vm_ops;
 	area->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
 	area->vm_private_data = hw->private_data;
@@ -232,18 +224,26 @@ int usx2y_hwdep_new(struct snd_card *card, struct usb_device *device)
 {
 	int err;
 	struct snd_hwdep *hw;
+	struct usx2ydev	*us428 = usx2y(card);
 
 	err = snd_hwdep_new(card, SND_USX2Y_LOADER_ID, 0, &hw);
 	if (err < 0)
 		return err;
 
 	hw->iface = SNDRV_HWDEP_IFACE_USX2Y;
-	hw->private_data = usx2y(card);
+	hw->private_data = us428;
 	hw->ops.dsp_status = snd_usx2y_hwdep_dsp_status;
 	hw->ops.dsp_load = snd_usx2y_hwdep_dsp_load;
 	hw->ops.mmap = snd_us428ctls_mmap;
 	hw->ops.poll = snd_us428ctls_poll;
 	hw->exclusive = 1;
 	sprintf(hw->name, "/dev/bus/usb/%03d/%03d", device->bus->busnum, device->devnum);
+
+	us428->us428ctls_sharedmem = alloc_pages_exact(US428_SHAREDMEM_PAGES, GFP_KERNEL);
+	if (!us428->us428ctls_sharedmem)
+		return -ENOMEM;
+	memset(us428->us428ctls_sharedmem, -1, US428_SHAREDMEM_PAGES);
+	us428->us428ctls_sharedmem->ctl_snapshot_last = -2;
+
 	return 0;
 }

sound/usb/usx2y/usbusx2y.c

@@ -375,6 +375,7 @@ static int usx2y_create_card(struct usb_device *device,
 	card->private_free = snd_usx2y_card_private_free;
 	usx2y(card)->dev = device;
 	init_waitqueue_head(&usx2y(card)->prepare_wait_queue);
+	init_waitqueue_head(&usx2y(card)->us428ctls_wait_queue_head);
 	mutex_init(&usx2y(card)->pcm_mutex);
 	INIT_LIST_HEAD(&usx2y(card)->midi_list);
 	strcpy(card->driver, "USB "NAME_ALLCAPS"");