On Mon, May 24, 2010 at 10:20:33PM +0800, Ming Lei wrote:
> On Mon, 24 May 2010 11:14:16 +0100
> Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote:
>
> > Right, I see what the problem is now - it's all to do with threads
> > created with kernel_thread() confusing lockdep.
> >
> > I'm of the opinion that all your changes in entry*.S are the wrong
> > way to fix this - not only does it add additional overhead where
> > none is really necessary, it adds additional complexity.
> >
> > So, here's a patch to solve the warning you quoted.
>
> No, your patch does not fix the issue, I still can see the lockdep
> warning after applying it against Linux 2.6.34-next-20100524.
No, my patch fixes the issue you raised in the dump. This is a new
lockdep issue which is unrelated to the first dump.
What's wrong is:
commit 0d928b0b616d1c5c5fe76019a87cba171ca91633
Author: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Date: Thu Aug 13 20:38:17 2009 +0200
Complete irq tracing support for ARM
Before this patch enabling and disabling irqs in assembler code and by
the hardware wasn't tracked completly.
I had to transpose two instructions in arch/arm/lib/bitops.h because
restore_irqs doesn't preserve the flags with CONFIG_TRACE_IRQFLAGS=y
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
which needs to be redone with a little more understanding, like the
following patch. Note: you will need the previous patch as well,
which is separate because it addresses a *different* issue.
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 7ee48e7..3fd7861 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -162,8 +162,6 @@ ENDPROC(__und_invalid)
@ r4 - orig_r0 (see pt_regs definition in ptrace.h)
@
stmia r5, {r0 - r4}
-
- asm_trace_hardirqs_off
.endm
.align 5
@@ -204,7 +202,7 @@ __dabt_svc:
@
@ IRQs off again before pulling preserved data off the stack
@
- disable_irq
+ disable_irq_notrace
@
@ restore SPSR and restart the instruction
@@ -218,6 +216,9 @@ ENDPROC(__dabt_svc)
__irq_svc:
svc_entry
+#ifdef CONFIG_TRACE_IRQFLAGS
+ bl trace_hardirqs_off
+#endif
#ifdef CONFIG_PREEMPT
get_thread_info tsk
ldr r8, [tsk, #TI_PREEMPT] @ get preempt count
@@ -291,7 +292,7 @@ __und_svc:
@
@ IRQs off again before pulling preserved data off the stack
@
-1: disable_irq
+1: disable_irq_notrace
@
@ restore SPSR and restart the instruction
@@ -327,7 +328,7 @@ __pabt_svc:
@
@ IRQs off again before pulling preserved data off the stack
@
- disable_irq
+ disable_irq_notrace
@
@ restore SPSR and restart the instruction
@@ -393,8 +394,6 @@ ENDPROC(__pabt_svc)
@ Clear FP to mark the first stack frame
@
zero_fp
-
- asm_trace_hardirqs_off
.endm
.macro kuser_cmpxchg_check
@@ -465,9 +464,6 @@ __irq_usr:
THUMB( movne r0, #0 )
THUMB( strne r0, [r0] )
#endif
-#ifdef CONFIG_TRACE_IRQFLAGS
- bl trace_hardirqs_on
-#endif
mov why, #0
b ret_to_user
--
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