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

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Date:	Thu, 22 Apr 2010 20:12:05 +0200
From:	Eric Lescouet <Eric.Lescouet@...tualLogix.com>
To:	Greg KH <gregkh@...e.de>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"usbip-devel@...ts.sourceforge.net" 
	<usbip-devel@...ts.sourceforge.net>
Subject: Re: [PATCH]: Fix deadlock in USBIP driver (staging), linux-2.6.34-rc5

Greg KH wrote:
[...]
> Ok, but does the lock_kernel() call you just made actually prevent this
> from happening?  Isn't there some other lock you can use instead?
> 

Right. lock_kernel() is not needed (was copy/paste).
The deadlock is avoided by not calling wait_for_completion()
when the code is executed by the "eh" thread itself.

> Also, to have patches that we can apply, we need a "Signed-off-by:"
> line.  See the file, Documentation/SubmittingPatches for what this
> means.

Understood.

> Your email client wrapped the patch and made it unappliable :(
> 
> thanks,
> 
> greg k-h

Sorry about that. Please find below an hopefully better one.
Thanks,
	Eric.


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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