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From: Hans Petter Selasky <hselasky@c2i.net>
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Date: Fri, 12 Nov 2010 09:56:04 +0100
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Cc: Matthew Fleming <matthew.fleming@isilon.com>
Subject: Re: sleep bug in taskqueue(9)
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On Thursday 29 April 2010 01:59:58 Matthew Fleming wrote:
> It looks to me like taskqueue_drain(taskqueue_thread, foo) will not
> correctly detect whether or not a task is currently running.  The check
> is against a field in the taskqueue struct, but for the taskqueue_thread
> queue with more than one thread, multiple threads can simultaneously be
> running a task, thus stomping over the tq_running field.
> 
> I have not seen any problem with the code as-is in actual use, so this
> is purely an inspection bug.
> 
> The following patch should fix the problem.  Because it changes the size
> of struct task I'm not sure if it would be suitable for MFC.
> 

1) The u_char is going to leave a hole in that structure on ARM platforms for 
example.

2) The existing taskqueue implementation also has a missing check for the 
pending count wrapping to zero. I.E. it should stick at 0xFFFF and not wrap to 
0.

--HPS