2007-05-03 20:10:20

by Daniel Walker

[permalink] [raw]
Subject: [PATCH -rt] wrong usage of smp_processor_id()

Found this while debugging with Steve .. trace_hardirqs_on() isn't always
called with interrupt off.

BUG: using smp_processor_id() in preemptible [00000000] code: init/1

caller is trace_hardirqs_on+0x16/0xe0
[<c01054b1>] show_trace_log_lvl+0x21/0x50
[<c0105c82>] show_trace+0x12/0x20
[<c0105d56>] dump_stack+0x16/0x20
[<c022c819>] debug_smp_processor_id+0xa9/0xb0
[<c0152a76>] trace_hardirqs_on+0x16/0xe0
[<c0103975>] do_notify_resume+0x115/0x7b0
[<c01044f4>] work_notifysig+0x13/0x1b
=======================
---------------------------
| preempt count: 00000001 ]
| 1-level deep critical section nesting:
----------------------------------------
.. [<c022c7c3>] .... debug_smp_processor_id+0x53/0xb0
.....[<c0152a76>] .. ( <= trace_hardirqs_on+0x16/0xe0)


Signed-Off-By: Daniel Walker <[email protected]>

---
kernel/latency_trace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6.21/kernel/latency_trace.c
===================================================================
--- linux-2.6.21.orig/kernel/latency_trace.c
+++ linux-2.6.21/kernel/latency_trace.c
@@ -105,7 +105,7 @@ static inline int DEBUG_WARN_ON(int cond
#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
# ifdef CONFIG_CRITICAL_PREEMPT_TIMING
static DEFINE_PER_CPU(int, trace_cpu_idle);
-# define irqs_off_preempt_count() (!__get_cpu_var(trace_cpu_idle) && preempt_count())
+# define irqs_off_preempt_count() (preempt_count() && !__get_cpu_var(trace_cpu_idle))
# else
# define irqs_off_preempt_count() 0
# endif
--

--


2007-05-03 20:14:03

by Steven Rostedt

[permalink] [raw]
Subject: Re: [PATCH -rt] wrong usage of smp_processor_id()

Daniel Walker wrote:

> ---
> kernel/latency_trace.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-2.6.21/kernel/latency_trace.c
> ===================================================================
> --- linux-2.6.21.orig/kernel/latency_trace.c
> +++ linux-2.6.21/kernel/latency_trace.c
> @@ -105,7 +105,7 @@ static inline int DEBUG_WARN_ON(int cond
> #ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
> # ifdef CONFIG_CRITICAL_PREEMPT_TIMING
> static DEFINE_PER_CPU(int, trace_cpu_idle);
> -# define irqs_off_preempt_count() (!__get_cpu_var(trace_cpu_idle) && preempt_count())
> +# define irqs_off_preempt_count() (preempt_count() && !__get_cpu_var(trace_cpu_idle))
> # else
> # define irqs_off_preempt_count() 0
> # endif

Ingo,

This is on top of one of my patches that I sent you (the cpu idle one).
So it's not for the 2.6.21-rt1, but if you apply my patch, this needs to
be added too.

Acked-by: Steven Rostedt <[email protected]>

-- Steve


2007-05-03 20:23:29

by Daniel Walker

[permalink] [raw]
Subject: Re: [PATCH -rt] wrong usage of smp_processor_id()

On Thu, 2007-05-03 at 16:12 -0400, Steven Rostedt wrote:
> Daniel Walker wrote:
>
> > ---
> > kernel/latency_trace.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > Index: linux-2.6.21/kernel/latency_trace.c
> > ===================================================================
> > --- linux-2.6.21.orig/kernel/latency_trace.c
> > +++ linux-2.6.21/kernel/latency_trace.c
> > @@ -105,7 +105,7 @@ static inline int DEBUG_WARN_ON(int cond
> > #ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
> > # ifdef CONFIG_CRITICAL_PREEMPT_TIMING
> > static DEFINE_PER_CPU(int, trace_cpu_idle);
> > -# define irqs_off_preempt_count() (!__get_cpu_var(trace_cpu_idle) && preempt_count())
> > +# define irqs_off_preempt_count() (preempt_count() && !__get_cpu_var(trace_cpu_idle))
> > # else
> > # define irqs_off_preempt_count() 0
> > # endif
>
> Ingo,
>
> This is on top of one of my patches that I sent you (the cpu idle one).
> So it's not for the 2.6.21-rt1, but if you apply my patch, this needs to
> be added too.

Isn't it a generic problem? It doesn't look specific to your change
unless you made some changes to entry.S .

Daniel

2007-05-03 20:32:56

by Steven Rostedt

[permalink] [raw]
Subject: Re: [PATCH -rt] wrong usage of smp_processor_id()

Daniel Walker wrote:

>>> Index: linux-2.6.21/kernel/latency_trace.c
>>> ===================================================================
>>> --- linux-2.6.21.orig/kernel/latency_trace.c
>>> +++ linux-2.6.21/kernel/latency_trace.c
>>> @@ -105,7 +105,7 @@ static inline int DEBUG_WARN_ON(int cond
>>> #ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
>>> # ifdef CONFIG_CRITICAL_PREEMPT_TIMING
>>> static DEFINE_PER_CPU(int, trace_cpu_idle);
>>> -# define irqs_off_preempt_count() (!__get_cpu_var(trace_cpu_idle) && preempt_count())
>>> +# define irqs_off_preempt_count() (preempt_count() && !__get_cpu_var(trace_cpu_idle))
>>> # else
>>> # define irqs_off_preempt_count() 0
>>> # endif


> Isn't it a generic problem? It doesn't look specific to your change
> unless you made some changes to entry.S .
>

See: http://lkml.org/lkml/2007/4/23/183

Specifically:


#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
# ifdef CONFIG_CRITICAL_PREEMPT_TIMING
-# define irqs_off_preempt_count() preempt_count()
+ static DEFINE_PER_CPU(int, trace_cpu_idle);
+# define irqs_off_preempt_count() (!__get_cpu_var(trace_cpu_idle) &&
preempt_count())
# else
# define irqs_off_preempt_count() 0
# endif
@@ -2153,6 +2154,20 @@ void notrace unmask_preempt_count(unsign
}
EXPORT_SYMBOL(unmask_preempt_count);


-- Steve

2007-05-03 20:34:54

by Daniel Walker

[permalink] [raw]
Subject: Re: [PATCH -rt] wrong usage of smp_processor_id()

On Thu, 2007-05-03 at 16:31 -0400, Steven Rostedt wrote:
> Daniel Walker wrote:
>
> >>> Index: linux-2.6.21/kernel/latency_trace.c
> >>> ===================================================================
> >>> --- linux-2.6.21.orig/kernel/latency_trace.c
> >>> +++ linux-2.6.21/kernel/latency_trace.c
> >>> @@ -105,7 +105,7 @@ static inline int DEBUG_WARN_ON(int cond
> >>> #ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
> >>> # ifdef CONFIG_CRITICAL_PREEMPT_TIMING
> >>> static DEFINE_PER_CPU(int, trace_cpu_idle);
> >>> -# define irqs_off_preempt_count() (!__get_cpu_var(trace_cpu_idle) && preempt_count())
> >>> +# define irqs_off_preempt_count() (preempt_count() && !__get_cpu_var(trace_cpu_idle))
> >>> # else
> >>> # define irqs_off_preempt_count() 0
> >>> # endif
>
>
> > Isn't it a generic problem? It doesn't look specific to your change
> > unless you made some changes to entry.S .
> >
>
> See: http://lkml.org/lkml/2007/4/23/183
>


Ahh, well safe bet I think.

Daniel