linux-kernel - [PATCH] f_midi_complete to call tasklet_hi

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Message-ID: <CAArt=Lh0S6UPX0OAhudTWxE7g7xbukQqHmuDAwCDwjBUbuJUnw@mail.gmail.com>
Date: Thu, 6 Feb 2025 12:23:13 -0700
From: Jillian Donahue <jilliandonahue58@...il.com>
To: gregkh@...uxfoundation.org, linux-usb@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH] f_midi_complete to call tasklet_hi_schedule

>From 9cb2628740d9f55f6f3faa5cce2de5eb8590f434 Mon Sep 17 00:00:00 2001
From: Jill Donahue <jilliandonahue58@...il.com>
Date: Thu, 6 Feb 2025 10:18:05 -0700
Subject: [PATCH] f_midi_complete to call tasklet_hi_schedule

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 tasklet_hi_schedule() to schedule the inner
f_midi_transmit() via a tasklet from the completion handler.

Link: https://lore.kernel.org/all/CAArt=LjxU0fUZOj06X+5tkeGT+6RbXzpWg1h4t4Fwa_KGVAX6g@mail.gmail>

Fixes: d5daf49b58661 ("USB: gadget: midi: add midi function driver")
Signed-off-by: Jill Donahue <jilliandonahue58@...il.com>
---
 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 837fcdfa3..37d438e5d 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);
+                       tasklet_hi_schedule(&midi->tasklet);
                        return;
                }
                break;
-- 
2.25.1