Re: Re: [PATCH] mips: add arch_trigger_all_cpu_backtrace() function

Re: Re: [PATCH] mips: add arch_trigger_all_cpu_backtrace() function

[Eunbong Song]

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> Hi Eubong,

> one small question inline ...

>> +void arch_trigger_all_cpu_backtrace(bool); +#define
>> arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace

> What is the purpose of this define ? is this maybe a leftover from
> some regex/cleanups ?

Hi John.
Actually, I just follow the same function of sparc architecture.
You can find this in arch/sparc/include/asm/irq_64.h as below

void arch_trigger_all_cpu_backtrace(bool);
#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace

I guess this is used for conditional compile. 
See below.
include/linux/nmi.h
#ifdef arch_trigger_all_cpu_backtrace
static inline bool trigger_all_cpu_backtrace(void)
{
        arch_trigger_all_cpu_backtrace(true);

        return true;
}
static inline bool trigger_allbutself_cpu_backtrace(void)
{
        arch_trigger_all_cpu_backtrace(false);
        return true;
}
#else
static inline bool trigger_all_cpu_backtrace(void)
{
        return false;
}
static inline bool trigger_allbutself_cpu_backtrace(void)
{
        return false;
}
#endif

Thanks. 
> John

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Re: [PATCH] mips: add arch_trigger_all_cpu_backtrace() function

[John Crispin]

On 22/10/2014 08:54, Eunbong Song wrote:
> 
>> Hi Eubong,
> 
>> one small question inline ...
> 
>>> +void arch_trigger_all_cpu_backtrace(bool); +#define
>>> arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
> 
>> What is the purpose of this define ? is this maybe a leftover from
>> some regex/cleanups ?
> 
> Hi John.
> Actually, I just follow the same function of sparc architecture.
> You can find this in arch/sparc/include/asm/irq_64.h as below
> 
> void arch_trigger_all_cpu_backtrace(bool);
> #define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
> 
> I guess this is used for conditional compile. 
> See below.
> include/linux/nmi.h
> #ifdef arch_trigger_all_cpu_backtrace
> static inline bool trigger_all_cpu_backtrace(void)
> {
>         arch_trigger_all_cpu_backtrace(true);
> 
>         return true;
> }
> static inline bool trigger_allbutself_cpu_backtrace(void)
> {
>         arch_trigger_all_cpu_backtrace(false);
>         return true;
> }
> #else
> static inline bool trigger_all_cpu_backtrace(void)
> {
>         return false;
> }
> static inline bool trigger_allbutself_cpu_backtrace(void)
> {
>         return false;
> }
> #endif
> 
> Thanks. 
>> John
> 

i don't see how this is required for conditional compiles. the code
define a->a which is bogus i think.

	John

Re: [PATCH] mips: add arch_trigger_all_cpu_backtrace() function

[James Hogan]

Hi John,

On Wed, Oct 22, 2014 at 09:11:39AM +0200, John Crispin wrote:
> On 22/10/2014 08:54, Eunbong Song wrote:
> >>> +void arch_trigger_all_cpu_backtrace(bool); +#define
> >>> arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
> > 
> >> What is the purpose of this define ? is this maybe a leftover from
> >> some regex/cleanups ?
> > 
> > Hi John.
> > Actually, I just follow the same function of sparc architecture.
> > You can find this in arch/sparc/include/asm/irq_64.h as below
> > 
> > void arch_trigger_all_cpu_backtrace(bool);
> > #define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
> > 
> > I guess this is used for conditional compile. 
> > See below.
> > include/linux/nmi.h
> > #ifdef arch_trigger_all_cpu_backtrace
> > static inline bool trigger_all_cpu_backtrace(void)
> > {
> >         arch_trigger_all_cpu_backtrace(true);
> > 
> >         return true;
> > }
> > static inline bool trigger_allbutself_cpu_backtrace(void)
> > {
> >         arch_trigger_all_cpu_backtrace(false);
> >         return true;
> > }
> > #else
> > static inline bool trigger_all_cpu_backtrace(void)
> > {
> >         return false;
> > }
> > static inline bool trigger_allbutself_cpu_backtrace(void)
> > {
> >         return false;
> > }
> > #endif
> > 
> > Thanks. 
> >> John
> > 
> 
> i don't see how this is required for conditional compiles. the code
> define a->a which is bogus i think.

It's a pretty common pattern in the asm headers, in order to allow
generic code to use the preprocessor to see whether it was defined or
not.

Cheers
James

[PATCH] mips: add arch_trigger_all_cpu_backtrace() function

[Eunbong Song]

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Currently, arch_trigger_all_cpu_backtrace() is defined in only x86 and sparc which has nmi interrupt.
But in case of softlockup not a hardlockup, it could be possible to dump backtrace of all cpus. and this could be helpful for debugging.

for example, if system has 2 cpus.

	CPU 0				CPU 1
 acquire read_lock()

				try to do write_lock()

 ,,,
 missing read_unlock()

In this case, softlockup will occur becasuse CPU 0 does not call read_unlock().
And dump_stack() print only backtrace for "CPU 0". If CPU1's backtrace is printed it's very helpful.

This patch adds arch_trigger_all_cpu_backtrace() for mips architecture.

Maybe someone make better patch than this. I just suggest the idea.
---
 arch/mips/include/asm/irq.h |    3 +++
 arch/mips/kernel/process.c  |   18 ++++++++++++++++++
 2 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/arch/mips/include/asm/irq.h b/arch/mips/include/asm/irq.h
index 39f07ae..5a4e1bb 100644
--- a/arch/mips/include/asm/irq.h
+++ b/arch/mips/include/asm/irq.h
@@ -48,4 +48,7 @@ extern int cp0_compare_irq;
 extern int cp0_compare_irq_shift;
 extern int cp0_perfcount_irq;
 
+void arch_trigger_all_cpu_backtrace(bool);
+#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
+
 #endif /* _ASM_IRQ_H */
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 636b074..9f51d3d 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -42,6 +42,7 @@
 #include <asm/isadep.h>
 #include <asm/inst.h>
 #include <asm/stacktrace.h>
+#include <asm/irq_regs.h>
 
 #ifdef CONFIG_HOTPLUG_CPU
 void arch_cpu_idle_dead(void)
@@ -532,3 +533,20 @@ unsigned long arch_align_stack(unsigned long sp)
 
 	return sp & ALMASK;
 }
+
+static void arch_dump_stack(void *info)
+{
+	struct pt_regs *regs;  
+	
+	regs = get_irq_regs();
+
+	if(regs)
+		show_regs(regs);
+
+	dump_stack();
+}
+
+void arch_trigger_all_cpu_backtrace(bool include_self)
+{
+	smp_call_function(arch_dump_stack, NULL, 1);
+}
-- 
1.7.0.1
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Re: [PATCH] mips: add arch_trigger_all_cpu_backtrace() function

[John Crispin]

Hi Eubong,

one small question inline ...

On 22/10/2014 08:39, Eunbong Song wrote:
> 
> Currently, arch_trigger_all_cpu_backtrace() is defined in only x86
> and sparc which has nmi interrupt. But in case of softlockup not a
> hardlockup, it could be possible to dump backtrace of all cpus. and
> this could be helpful for debugging.
> 
> for example, if system has 2 cpus.
> 
> CPU 0				CPU 1 acquire read_lock()
> 
> try to do write_lock()
> 
> ,,, missing read_unlock()
> 
> In this case, softlockup will occur becasuse CPU 0 does not call
> read_unlock(). And dump_stack() print only backtrace for "CPU 0".
> If CPU1's backtrace is printed it's very helpful.
> 
> This patch adds arch_trigger_all_cpu_backtrace() for mips
> architecture.
> 
> Maybe someone make better patch than this. I just suggest the
> idea. --- arch/mips/include/asm/irq.h |    3 +++ 
> arch/mips/kernel/process.c  |   18 ++++++++++++++++++ 2 files
> changed, 21 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/mips/include/asm/irq.h
> b/arch/mips/include/asm/irq.h index 39f07ae..5a4e1bb 100644 ---
> a/arch/mips/include/asm/irq.h +++ b/arch/mips/include/asm/irq.h @@
> -48,4 +48,7 @@ extern int cp0_compare_irq; extern int
> cp0_compare_irq_shift; extern int cp0_perfcount_irq;
> 
> +void arch_trigger_all_cpu_backtrace(bool); +#define
> arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace

What is the purpose of this define ? is this maybe a leftover from
some regex/cleanups ?

	John


> + #endif /* _ASM_IRQ_H */ diff --git a/arch/mips/kernel/process.c
> b/arch/mips/kernel/process.c index 636b074..9f51d3d 100644 ---
> a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@
> -42,6 +42,7 @@ #include <asm/isadep.h> #include <asm/inst.h> 
> #include <asm/stacktrace.h> +#include <asm/irq_regs.h>
> 
> #ifdef CONFIG_HOTPLUG_CPU void arch_cpu_idle_dead(void) @@ -532,3
> +533,20 @@ unsigned long arch_align_stack(unsigned long sp)
> 
> return sp & ALMASK; } + +static void arch_dump_stack(void *info) 
> +{ +	struct pt_regs *regs; + +	regs = get_irq_regs(); + +	if(regs) 
> +		show_regs(regs); + +	dump_stack(); +} + +void
> arch_trigger_all_cpu_backtrace(bool include_self) +{ +
> smp_call_function(arch_dump_stack, NULL, 1); +}
> 

Re: [PATCH] mips: add arch_trigger_all_cpu_backtrace() function

[Ralf Baechle]

On Wed, Oct 22, 2014 at 06:39:56AM +0000, Eunbong Song wrote:

Applying - but:

> +	if(regs)
         ^^^

There should be a blank between if and opening parenthesis.

  Ralf

Re: [PATCH] mips: add arch_trigger_all_cpu_backtrace() function

[James Hogan]

On Wed, Oct 22, 2014 at 06:39:56AM +0000, Eunbong Song wrote:
> This patch adds arch_trigger_all_cpu_backtrace() for mips architecture.

Don't forget your Signed-off-by

> +static void arch_dump_stack(void *info)
> +{
> +	struct pt_regs *regs;  
> +	
> +	regs = get_irq_regs();
> +
> +	if(regs)
> +		show_regs(regs);
> +
> +	dump_stack();
> +}
> +
> +void arch_trigger_all_cpu_backtrace(bool include_self)
> +{
> +	smp_call_function(arch_dump_stack, NULL, 1);

should this call arch_dump_stack directly too if include_self?

Cheers
James