linux-kernel - Re: BUG: lock held when returning to user space

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Message-Id: <1205430974.10894.86.camel@localhost.localdomain>
Date:	Thu, 13 Mar 2008 10:56:14 -0700
From:	Daniel Walker <dwalker@...sta.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Frank Munzert <frankm@...ux.vnet.ibm.com>, mingo@...e.hu,
	linux-kernel@...r.kernel.org
Subject: Re: BUG: lock held when returning to user space


On Thu, 2008-03-13 at 18:39 +0100, Peter Zijlstra wrote:

> > These need to be removed, but the usage is clearly not compatible with
> > the mutex API ..
> > 
> > If you convert them to atomic counts then you loose the sleeping aspect
> > of the semaphore, which you'd have to add back somehow.
> > 
> > The only API that seems straight forward is using complete's .. Then you
> > get an atomic count and all the sleeping function calls you might want..
> > (include/linux/completion.h) The problem with complete's is that you
> > can't start them out at "1" or "completed" unless you actually run
> > complete() once during initialization (that's kind of ugly) ..
> 
> A simple waitqueue would work.

I was just mulling over what the most straight forward way would be.. I
thought about wait queues, but the API didn't seem as easy to use a
completes..

Daniel

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