linux-kernel - [PATCH v4] f_midi_complete to call queue

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Message-Id: <20250211174805.1369265-1-jdonahue@fender.com>
Date: Tue, 11 Feb 2025 10:48:05 -0700
From: Jill Donahue <jilliandonahue58@...il.com>
To: gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Jill Donahue <jilliandonahue58@...il.com>,
	stable@...r.kernel.org
Subject: [PATCH v4] f_midi_complete to call queue_work

From: Jill Donahue <jilliandonahue58@...il.com>

When using USB MIDI, a lock is attempted to be acquired twice through a
re-entrant call to f_midi_transmit, causing a deadlock.

Fix it by using queue_work() to schedule the inner f_midi_transmit() via
a high priority work queue from the completion handler.

Link: https://lore.kernel.org/all/CAArt=LjxU0fUZOj06X+5tkeGT+6RbXzpWg1h4t4Fwa_KGVAX6g@mail.gmail.com/
Fixes: d5daf49b58661 ("USB: gadget: midi: add midi function driver")
Cc: stable@...r.kernel.org
Signed-off-by: Jill Donahue <jilliandonahue58@...il.com>
---
V3 -> V4: Adjusted changes based on latest kernel tree

 drivers/usb/gadget/function/f_midi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
index 837fcdfa3840..a188648d7528 100644
--- a/drivers/usb/gadget/function/f_midi.c
+++ b/drivers/usb/gadget/function/f_midi.c
@@ -283,7 +283,7 @@ f_midi_complete(struct usb_ep *ep, struct usb_request *req)
 			/* Our transmit completed. See if there's more to go.
 			 * f_midi_transmit eats req, don't queue it again. */
 			req->length = 0;
-			f_midi_transmit(midi);
+			queue_work(system_highpri_wq, &midi->work);
 			return;
 		}
 		break;
-- 
2.25.1