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

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Date:	Thu, 22 Apr 2010 18:54:02 +0200
From:	Eric Lescouet <Eric.Lescouet@...tualLogix.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
CC:	"usbip-devel@...ts.sourceforge.net" 
	<usbip-devel@...ts.sourceforge.net>
Subject: [PATCH]: Fix deadlock in USBIP driver (staging), linux-2.6.34-rc5

Hi,
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.
The patch checks if "eh" is the current thread, in usbip_stop_eh().

Please Cc me in reply, I'm not in the list.

b.r.

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

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 17:07:36.249588273 +0200
@@ -116,6 +116,13 @@
  void usbip_stop_eh(struct usbip_device *ud)
  {
      struct usbip_task *eh = &ud->eh;
+    int                i_am_eh;
+
+    lock_kernel();
+    i_am_eh = (eh->thread == current);
+    unlock_kernel();
+    if (i_am_eh)
+        return; /* do not wait for myself */

      wait_for_completion(&eh->thread_done);
      usbip_dbg_eh("usbip_eh has finished\n");

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