* Pekka Enberg <penberg@xxxxxxxxxx> wrote:
> On Mon, Mar 28, 2011 at 9:19 AM, Ingo Molnar <mingo@xxxxxxx> wrote:
> >> Tejun, does this look good to you as well? I think it should go
> >> through the percpu tree. It's needed to fix a boot crash with
> >> lockless SLUB fastpaths enabled.
> >
> > AFAICS Linus applied it already:
> >
> > d7c3f8cee81f: percpu: Omit segment prefix in the UP case for cmpxchg_double
>
> Oh, I missed that. Did you test the patch, Ingo? It's missing attributions
> and reference to the LKML discussion unfortunately...
I think we might still be missing the hunk below - or is it now not needed
anymore?
Thanks,
Ingo
-------------->
>From 53c0eceb7bf64f2a89c59ae4f14a676fa4128462 Mon Sep 17 00:00:00 2001
From: Christoph Lameter <cl@xxxxxxxxx>
Date: Sat, 26 Mar 2011 14:49:56 -0500
Subject: [PATCH] per_cpu: Fix cmpxchg_double() for !SMP
cmpxchg_double() should only be provided for SMP. In the UP case
the GS register is not defined and the function will fail.
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: torvalds@xxxxxxxxxxxxxxxxxxxx
Cc: tj@xxxxxxxxxx
Cc: npiggin@xxxxxxxxx
Cc: rientjes@xxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
LKML-Reference: <alpine.DEB.2.00.1103261440160.25375@xxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
arch/x86/include/asm/percpu.h | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index a09e1f0..52330a4 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -507,6 +507,7 @@ do { \
* it in software. The address used in the cmpxchg16 instruction must be
* aligned to a 16 byte boundary.
*/
+#ifdef CONFIG_SMP
#define percpu_cmpxchg16b_double(pcp1, o1, o2, n1, n2) \
({ \
char __ret; \
@@ -529,6 +530,7 @@ do { \
#define irqsafe_cpu_cmpxchg_double_8(pcp1, pcp2, o1, o2, n1, n2) percpu_cmpxchg16b_double(pcp1, o1, o2, n1, n2)
#endif
+#endif
/* This is not atomic against other CPUs -- CPU preemption needs to be off */
#define x86_test_and_clear_bit_percpu(bit, var) \
--
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