From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH] unicore32 fix: remove arch-specific futex support
Date: Wed, 30 Mar 2011 14:40:03 +0200
Message-ID: <201103301440.03479.arnd@arndb.de>
References: <01eb01cbeeb7$30390460$90ab0d20$@mprc.pku.edu.cn> <201103301417.20027.arnd@arndb.de> <alpine.LFD.2.00.1103301421390.22418@localhost6.localdomain6>
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To: Thomas Gleixner <tglx@linutronix.de>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>, Paul Mundt <lethal@linux-sh.org>, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org

On Wednesday 30 March 2011, Thomas Gleixner wrote:
> The problem is that you need cmpxchg in user space as well.
> 
> ARM does this with some syscall magic for machines which do not have
> cmpxchg.

Ah, right. I wonder how sh does it.

I also remember that the original unicore32 ABI had support for a cmpxchg
system call, but that was removed with the move to the generic syscall
table.

It is of course possible to add it back using the __NR_arch_specific_syscall
entry point.

	Arnd