linux-kernel - [022/117] staging: usbip: Fix deadlock

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Message-Id: <20100510223319.190984548@kvm.kroah.org>
Date:	Mon, 10 May 2010 15:31:53 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Eric Lescouet <eric@...couet.org>
Subject: [022/117] staging: usbip: Fix deadlock

2.6.33-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Eric Lescouet <lescouet@...tuallogix.com>

commit d01f42a22ef381ba973958e977209ac9a8667d57 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/staging/usbip/usbip_event.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/staging/usbip/usbip_event.c
+++ b/drivers/staging/usbip/usbip_event.c
@@ -117,6 +117,9 @@ void usbip_stop_eh(struct usbip_device *
 {
 	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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