[PATCH 1/1] trace: use the more accurate parameter.

[PATCH 1/1] trace: use the more accurate parameter.

[Wenji Huang]

Pass tsk to __update_max_tr instead of current to avoid latent hazard.

Impact: clean up

Signed-off-by: Wenji Huang <wenji.huang@oracle.com>
---
 kernel/trace/trace.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 5b1e9a9..c1592f1 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -335,7 +335,7 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
 	data->rt_priority = tsk->rt_priority;
 
 	/* record this tasks comm */
-	tracing_record_cmdline(current);
+	tracing_record_cmdline(tsk);
 }
 
 static void
-- 
1.5.6

Re: [PATCH 1/1] trace: use the more accurate parameter.

[Frederic Weisbecker]

On Mon, Feb 09, 2009 at 07:30:04PM -0500, Wenji Huang wrote:
> Pass tsk to __update_max_tr instead of current to avoid latent hazard.
> 
> Impact: clean up
> 
> Signed-off-by: Wenji Huang <wenji.huang@oracle.com>
> ---
>  kernel/trace/trace.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 5b1e9a9..c1592f1 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -335,7 +335,7 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
>  	data->rt_priority = tsk->rt_priority;
>  
>  	/* record this tasks comm */
> -	tracing_record_cmdline(current);
> +	tracing_record_cmdline(tsk);
>  }


Indeed. At this stage, tsk is the next task in the middle of a context
switch. So I guess current is right, but this is more proper to use tsk.

  
>  static void
> -- 
> 1.5.6
> 
> --
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Re: [PATCH 1/1] trace: use the more accurate parameter.

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Mon, Feb 09, 2009 at 07:30:04PM -0500, Wenji Huang wrote:
> > Pass tsk to __update_max_tr instead of current to avoid latent hazard.
> > 
> > Impact: clean up
> > 
> > Signed-off-by: Wenji Huang <wenji.huang@oracle.com>
> > ---
> >  kernel/trace/trace.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index 5b1e9a9..c1592f1 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -335,7 +335,7 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
> >  	data->rt_priority = tsk->rt_priority;
> >  
> >  	/* record this tasks comm */
> > -	tracing_record_cmdline(current);
> > +	tracing_record_cmdline(tsk);
> >  }
> 
> 
> Indeed. At this stage, tsk is the next task in the middle of a context
> switch. So I guess current is right, but this is more proper to use tsk.

Rename it to 'next' then please.

	Ingo

Re: [PATCH 1/1] trace: use the more accurate parameter.

[Steven Rostedt]

On Wed, 11 Feb 2009, Ingo Molnar wrote:

> 
> * Frederic Weisbecker <fweisbec@gmail.com> wrote:
> 
> > On Mon, Feb 09, 2009 at 07:30:04PM -0500, Wenji Huang wrote:
> > > Pass tsk to __update_max_tr instead of current to avoid latent hazard.
> > > 
> > > Impact: clean up
> > > 
> > > Signed-off-by: Wenji Huang <wenji.huang@oracle.com>
> > > ---
> > >  kernel/trace/trace.c |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > > 
> > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > > index 5b1e9a9..c1592f1 100644
> > > --- a/kernel/trace/trace.c
> > > +++ b/kernel/trace/trace.c
> > > @@ -335,7 +335,7 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
> > >  	data->rt_priority = tsk->rt_priority;
> > >  
> > >  	/* record this tasks comm */
> > > -	tracing_record_cmdline(current);
> > > +	tracing_record_cmdline(tsk);
> > >  }
> > 
> > 
> > Indeed. At this stage, tsk is the next task in the middle of a context
> > switch. So I guess current is right, but this is more proper to use tsk.
> 
> Rename it to 'next' then please.

I'm sorry, I missed this comment, and only notice it because of Wenji's 
latest patches.

For the __update_max_tr used by irqsoff, this is not the case. The 
update_max_tr is just to make a snapshot of the latest max. The 
irq/preempt latency tracers do not use the sched switch to record comms, 
especially since it only cares when a new max happens. There is no concept 
of a 'next' task.

I think the proper name is 'task'.

-- Steve