linux-kernel - [PATCH 2/2] um: Disable CONFIG_CMPXCHG

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Message-Id: <1302698512-11979-2-git-send-email-richard@nod.at>
Date:	Wed, 13 Apr 2011 14:41:52 +0200
From:	Richard Weinberger <richard@....at>
To:	akpm@...ux-foundation.com
Cc:	slyich@...il.com, linux-kernel@...r.kernel.org, jdike@...toit.com,
	user-mode-linux-devel@...ts.sourceforge.net,
	Richard Weinberger <richard@....at>
Subject: [PATCH 2/2] um: Disable CONFIG_CMPXCHG_LOCAL

Commit 8a5ec0ba "Lockless (and preemptless) fastpaths for slub"
makes use of this_cpu_cmpxchg_double() which needs
this_cpu_cmpxchg16b_emu() on x86_64.
Implementing cmpxchg16b emulation for UML would introduce
too much complexity. So just disable it.

LKML-Reference: <20110412192014.GF16342@....dyndns.org>
Reported-by: Sergei Trofimovich <slyich@...il.com>
Signed-off-by: Richard Weinberger <richard@....at>
---
 arch/um/Kconfig.x86 |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/um/Kconfig.x86 b/arch/um/Kconfig.x86
index 02fb017..a9da516 100644
--- a/arch/um/Kconfig.x86
+++ b/arch/um/Kconfig.x86
@@ -4,6 +4,10 @@ menu "UML-specific options"
 
 menu "Host processor type and features"
 
+config CMPXCHG_LOCAL
+	bool
+	default n
+
 source "arch/x86/Kconfig.cpu"
 
 endmenu
-- 
1.6.6.1

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