linux-kernel - [PATCH]: Fix deadlock in USBIP driver (staging), linux-2.6.34-rc5

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Message-Id: <201004240055.o3O0tOCP016954@localhost.localdomain>
Date:	Sat, 24 Apr 2010 02:55:24 +0200
From:	Eric Lescouet <lescouet@...tuallogix.com>
To:	Greg KH <greg@...ah.com>
CC:	linux-kernel@...r.kernel.org
Subject: [PATCH]: Fix deadlock in USBIP driver (staging), linux-2.6.34-rc5

Resent with hopefully everything ...

When detaching a port from the client side (usbip --detach 0),
the event thread, on the server side, is going to deadlock.
The "eh" server thread is getting USBIP_EH_RESET event and calls:
  -> stub_device_reset() -> usb_reset_device()
the USB framework is then calling back _in the same "eh" thread_ :
  -> stub_disconnect() -> usbip_stop_eh() -> wait_for_completion()
the "eh" thread is being asleep forever, waiting for its own completion.
This patch checks if "eh" is the current thread, in usbip_stop_eh().

Signed-off-by: Eric Lescouet <eric@...couet.org>
---

diff -Nur linux-2.6.34-rc5/drivers/staging/usbip/usbip_event.c linux-2.6.34-rc5.new/drivers/staging/usbip/usbip_event.c
--- linux-2.6.34-rc5/drivers/staging/usbip/usbip_event.c	2010-04-20 01:29:56.000000000 +0200
+++ linux-2.6.34-rc5.new/drivers/staging/usbip/usbip_event.c	2010-04-22 19:19:52.997889126 +0200
@@ -117,6 +117,9 @@
 {
 	struct usbip_task *eh = &ud->eh;
 
+	if (eh->thread == current)
+		return; /* do not wait for myself */
+
 	wait_for_completion(&eh->thread_done);
 	usbip_dbg_eh("usbip_eh has finished\n");
 }
--
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