linux-kernel - Re: start_kernel(): bug: interrupts were enabled early

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Message-ID: <20100401094111.GB29433@shareable.org>
Date:	Thu, 1 Apr 2010 10:41:11 +0100
From:	Jamie Lokier <jamie@...reable.org>
To:	David Howells <dhowells@...hat.com>
Cc:	Russell King <rmk@....linux.org.uk>,
	Yinghai Lu <yinghai@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rabin Vincent <rabin@....in>,
	lkml <linux-kernel@...r.kernel.org>, hpa@...or.com,
	penberg@...helsinki.fi, cl@...ux-foundation.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linux-arch@...r.kernel.org
Subject: Re: start_kernel(): bug: interrupts were enabled early

David Howells wrote:
> Russell King <rmk@....linux.org.uk> wrote:
> > We use the standard generic kernel implementation.  Is x86 different? ;)
> 
> The optimised fast paths used on x86 rwsems don't disable interrupts.

Any reason not to use the same technique for all the archs - plus the
trick used in arch/armkernel/entry-armv.S:__kuser_cmpxchg for those
archs which don't have atomic instructions or ll/sc?

If the problem here is _only_ semaphores, and the above might make
semaphores faster anyway, perhaps it's a solution.

-- Jamie
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