From: Linus Torvalds <torvalds@woody.linux-foundation.org>
Date: Wed, 1 Aug 2007 04:12:07 +0000 (-0700)
Subject: Fix WARN_ON() on bitfield ops
X-Git-Tag: v2.6.23-rc2~28
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8d4fbcfbe0a4bfc73e7f0297c59ae514e1f1436f;p=pandora-kernel.git

Fix WARN_ON() on bitfield ops

Alexey Dobriyan noticed that the new WARN_ON() semantics that were
introduced by commit 684f978347deb42d180373ac4c427f82ef963171 (to also
return the value to be warned on) didn't compile when given a bitfield,
because the typeof doesn't work for bitfields.

So instead of the typeof trick, use an "int" variable together with a
"!!(x)" expression, as suggested by Al Viro.

To make matters more interesting, Paul Mackerras points out that that is
sub-optimal on Power, but the old asm-coded comparison seems to be buggy
anyway on 32-bit Power if the conditional was 64-bit, so I think there
are more problems there.

Regardless, the new WARN_ON() semantics may have been a bad idea.  But
this at least avoids the more serious complications.

Cc: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

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