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Date: Wed, 28 May 2008 17:43:10 +0100
From: "Bruce M. Simpson" <bms@FreeBSD.org>
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To: Marcel Moolenaar <marcel@FreeBSD.org>
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Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/ia64/include atomic.h
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Marcel Moolenaar wrote:
> ...the cmpxchg instruction was comparing
>   0x0000000080000000LU to 0xffffffff80000000LU and obviously didn't
>   perform the exchange.
>   
>   ...Subsequent locking requests found rw_state non-zero
>   and the thread in question entered the kernel and block indefinitely.


Man, this must have been a total nightmare to track down. I guess the 
bigger question is, why was gcc sign-extending a constant marked U in 
the first place?