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Date: Mon, 28 Oct 2002 22:43:26 +0100
From: Manfred Spraul <manfred@colorfullife.com>
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To: Peter Waechtler <pwaechtler@mac.com>
CC: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] unified SysV and Posix mqueues as FS
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Peter Waechtler wrote:

>>For the locking stuff, the patch should probably depend on the sysv rcu
>>patch, it cleans up locking a bit.
>>
>>    
>>
>
>Well, I am a victim of "information hiding" ;-)
>  
>
That's not information hiding - there were 3 different locking 
implementations: first one with a per-queue spinlock that didn't support 
growing the number of queues at runtime, then one with a global rw lock 
and a per-queue spinlock, and the simple, global spinlock version that's 
part of 2.3.x-2.5.4x.

>msq_lock(id) does not lock a queue, it locks/unlocks the whole array.
>Forget my post about a deadlock in ipc_addid()
>  
>
Which deadlock did you see? With the RCU ipc patch [part of 2.5.44-mm6], 
msg_lock again locks the queue, not the whole array. Calls to 
ipc_addid() with the msq spinlock aquired are not permitted.

--
    Manfred

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