[PATCH 01/01] arm: fix a preempt_count() corruption for CONFIG_PREEMPT=n

[PATCH 01/01] arm: fix a preempt_count() corruption for CONFIG_PREEMPT=n

[Patrik, Kluba]

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Hi All,

After a hard days' work, I've managed to track down a ghost causing
sporadic kernel warnings and system crashes. The patch applies for the
HEAD of linux-stable. I don't know how to create and submit patches
correctly, and hope that somebody will pick it up...

Regards,
Patrik

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[-- Type: text/x-patch, Size: 1012 bytes --]

>From 4dd31e88a2715389e5ac198dcf00b48b4f148ea6 Mon Sep 17 00:00:00 2001
From: Patrik Kluba <pkluba@dension.com>
Date: Fri, 14 Dec 2012 14:36:27 +0100
Subject: [PATCH] arm: fix a preempt_count() corruption for CONFIG_PREEMPT=n

All the preempt-disabling assembly code is under CONFIG_PREEMPT,
while VFP_bounce calls preempt_enable() uncoditionally, leading to
a preempt_count() corruption (gets set to 0xffffffff). Fix the
imbalance by adding #ifdef CONFIG_PREEMPT before preempt_enable().
---
 arch/arm/vfp/vfpmodule.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 3b44e0d..2184f7e 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -428,7 +428,10 @@ void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
 	if (exceptions)
 		vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
  exit:
+#ifdef CONFIG_PREEMPT
 	preempt_enable();
+#endif
+	return;
 }
 
 static void vfp_enable(void *unused)
-- 
1.7.10.4

[PATCH 01/01] arm: fix a preempt_count() corruption for CONFIG_PREEMPT=n

[Patrik, Kluba]

On Fri, 04 Jan 2013 14:21:46 -0800
Stephen Boyd <sboyd@codeaurora.org> wrote:

> On 01/03/13 23:48, Patrik, Kluba wrote:
> > Sorry for being late, was on holiday. Yes, you were right,
> > CONFIG_DEBUG_PREEMPT (after breaking dependency on CONFIG_PREEMPT -
> > this is how I caught the exact place) and CONFIG_DEBUG_ATOMIC_SLEEP
> > was enabled due to bug hunting in own code (and found yet another
> > at an unexpected place). 
> > I have chosen #ifdef CONFIG_PREEMPT to match with assembly code, but
> > your solution seems more reasonable.
> 
> Did you test my patch? If so, can I get your tested by please so I can
> stick it in the patch tracker?

Yes, I have tested it. Here you are:

Tested-by: Patrik Kluba <pkluba@dension.com>

Bye,
Patrik

[PATCH 01/01] arm: fix a preempt_count() corruption for CONFIG_PREEMPT=n

[Stephen Boyd]

On 01/03/13 23:48, Patrik, Kluba wrote:
> Sorry for being late, was on holiday. Yes, you were right,
> CONFIG_DEBUG_PREEMPT (after breaking dependency on CONFIG_PREEMPT -
> this is how I caught the exact place) and CONFIG_DEBUG_ATOMIC_SLEEP was
> enabled due to bug hunting in own code (and found yet another at an
> unexpected place). 
> I have chosen #ifdef CONFIG_PREEMPT to match with assembly code, but
> your solution seems more reasonable.

Did you test my patch? If so, can I get your tested by please so I can
stick it in the patch tracker?

Thanks,
Stephen

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

[PATCH 01/01] arm: fix a preempt_count() corruption for CONFIG_PREEMPT=n

[Patrik, Kluba]

On Wed, 02 Jan 2013 16:41:00 -0800
Stephen Boyd <sboyd@codeaurora.org> wrote:

> On 12/18/12 16:01, Russell King - ARM Linux wrote:
> > On Tue, Dec 18, 2012 at 03:54:12PM -0800, Stephen Boyd wrote:
> >> Can you try this patch? I'll probably send a follow up patch that
> >> consolidates the duplicated preempt_decrement code into some
> >> assembly macro. We may also want to fix it up so that assembly
> >> stubs call into the preempt tracer. I'm not sure how that works
> >> right now with VFP.
> > This looks like a sensible fix to me - once tested of course.
> 
> Kluba, did the patch work for you?
> 

Sorry for being late, was on holiday. Yes, you were right,
CONFIG_DEBUG_PREEMPT (after breaking dependency on CONFIG_PREEMPT -
this is how I caught the exact place) and CONFIG_DEBUG_ATOMIC_SLEEP was
enabled due to bug hunting in own code (and found yet another at an
unexpected place). 
I have chosen #ifdef CONFIG_PREEMPT to match with assembly code, but
your solution seems more reasonable.

Regards,
Patrik

-- 
Patrik KLUBA
Software Developer at

DENSION Audio Systems Ltd.
H-1116 Budapest, Sztregova u. 1
Phone: +36 1 463 0470
Fax:   +36 1 463 0479
Web:   www.dension.com

[PATCH 01/01] arm: fix a preempt_count() corruption for CONFIG_PREEMPT=n

[Patrik, Kluba]

Hi All,

After a hard days' work, I've managed to track down a ghost causing
sporadic kernel warnings and system crashes. The patch applies for the
HEAD of linux-stable. I don't know how to create and submit patches
correctly, and hope that somebody will pick it up...

Regards,
Patrik
---
>From 4dd31e88a2715389e5ac198dcf00b48b4f148ea6 Mon Sep 17 00:00:00 2001
From: Patrik Kluba <pkluba@dension.com>
Date: Fri, 14 Dec 2012 14:36:27 +0100
Subject: [PATCH] arm: fix a preempt_count() corruption for
CONFIG_PREEMPT=n

All the preempt-disabling assembly code is under CONFIG_PREEMPT,
while VFP_bounce calls preempt_enable() uncoditionally, leading to
a preempt_count() corruption (gets set to 0xffffffff). Fix the
imbalance by adding #ifdef CONFIG_PREEMPT before preempt_enable().
---
 arch/arm/vfp/vfpmodule.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 3b44e0d..2184f7e 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -428,7 +428,10 @@ void VFP_bounce(u32 trigger, u32 fpexc, struct
pt_regs *regs) if (exceptions)
 		vfp_raise_exceptions(exceptions, trigger, orig_fpscr,
regs); exit:
+#ifdef CONFIG_PREEMPT
 	preempt_enable();
+#endif
+	return;
 }
 
 static void vfp_enable(void *unused)
-- 
1.7.10.4