linux-kernel - Re: [PATCH v2] trace: module: Maintain a valid user count

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Date:	Thu, 6 Mar 2014 12:34:03 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ingo Molnar <mingo@...hat.com>
Cc:	Romain Izard <romain.izard.pro@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] trace: module: Maintain a valid user count

Ingo,

You want to push this to Linus?

Reviewed-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve


On Tue,  4 Mar 2014 10:09:39 +0100
Romain Izard <romain.izard.pro@...il.com> wrote:

> The replacement of the 'count' variable by two variables 'incs' and
> 'decs' to resolve some race conditions during module unloading was done
> in parallel with some cleanup in the trace subsystem, and was integrated
> as a merge.
> 
> Unfortunately, the formula for this replacement was wrong in the tracing
> code, and the refcount in the traces was not usable as a result.
> 
> Use 'count = incs - decs' to compute the user count.
> 
> Signed-off-by: Romain Izard <romain.izard.pro@...il.com>
> ---
>  include/trace/events/module.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/trace/events/module.h b/include/trace/events/module.h
> index 161932737416..ca298c7157ae 100644
> --- a/include/trace/events/module.h
> +++ b/include/trace/events/module.h
> @@ -78,7 +78,7 @@ DECLARE_EVENT_CLASS(module_refcnt,
>  
>  	TP_fast_assign(
>  		__entry->ip	= ip;
> -		__entry->refcnt	= __this_cpu_read(mod->refptr->incs) + __this_cpu_read(mod->refptr->decs);
> +		__entry->refcnt	= __this_cpu_read(mod->refptr->incs) - __this_cpu_read(mod->refptr->decs);
>  		__assign_str(name, mod->name);
>  	),
>  

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