This is a note to let you know that I've just added the patch titled
ARM: 7417/1: vfp: ensure preemption is disabled when enabling VFP access
to the 3.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-7417-1-vfp-ensure-preemption-is-disabled-when-enabling-vfp-access.patch
and it can be found in the queue-3.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 998de4acb2ba188d20768d1065658377a2e7d29b Mon Sep 17 00:00:00 2001
From: Will Deacon <[email protected]>
Date: Fri, 11 May 2012 17:42:37 +0100
Subject: ARM: 7417/1: vfp: ensure preemption is disabled when enabling VFP
access
From: Will Deacon <[email protected]>
commit 998de4acb2ba188d20768d1065658377a2e7d29b upstream.
The vfp_enable function enables access to the VFP co-processor register
space (cp10 and cp11) on the current CPU and must be called with
preemption disabled. Unfortunately, the vfp_init late initcall does not
disable preemption and can lead to an oops during boot if thread
migration occurs at the wrong time and we end up attempting to access
the FPSID on a CPU with VFP access disabled.
This patch fixes the initcall to call vfp_enable from a non-preemptible
context on each CPU and adds a BUG_ON(preemptible) to ensure that any
similar problems are easily spotted in the future.
Reported-by: Hyungwoo Yang <[email protected]>
Signed-off-by: Hyungwoo Yang <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
Signed-off-by: Russell King <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/arm/vfp/vfpmodule.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -11,6 +11,7 @@
#include <linux/types.h>
#include <linux/cpu.h>
#include <linux/cpu_pm.h>
+#include <linux/hardirq.h>
#include <linux/kernel.h>
#include <linux/notifier.h>
#include <linux/signal.h>
@@ -428,7 +429,10 @@ void VFP_bounce(u32 trigger, u32 fpexc,
static void vfp_enable(void *unused)
{
- u32 access = get_copro_access();
+ u32 access;
+
+ BUG_ON(preemptible());
+ access = get_copro_access();
/*
* Enable full access to VFP (cp10 and cp11)
@@ -556,7 +560,7 @@ static int __init vfp_init(void)
unsigned int cpu_arch = cpu_architecture();
if (cpu_arch >= CPU_ARCH_ARMv6)
- vfp_enable(NULL);
+ on_each_cpu(vfp_enable, NULL, 1);
/*
* First check that there is a VFP that we can use.
@@ -577,8 +581,6 @@ static int __init vfp_init(void)
} else {
hotcpu_notifier(vfp_hotplug, 0);
- smp_call_function(vfp_enable, NULL, 1);
-
VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT; /*
Extract the architecture version */
printk("implementor %02x architecture %d part %02x variant %x
rev %x\n",
(vfpsid & FPSID_IMPLEMENTER_MASK) >>
FPSID_IMPLEMENTER_BIT,
Patches currently in stable-queue which might be from [email protected] are
queue-3.3/arm-7417-1-vfp-ensure-preemption-is-disabled-when-enabling-vfp-access.patch
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