linux-kernel - Re: [PATCH] tracing/function-return-tracer: clean up task start/exit callbacks

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Message-ID: <c62985530811230811q633349e5neb79fb6841c642ff@mail.gmail.com>
Date:	Sun, 23 Nov 2008 17:11:41 +0100
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Steven Rostedt" <rostedt@...dmis.org>,
	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing/function-return-tracer: clean up task start/exit callbacks

2008/11/23 Ingo Molnar <mingo@...e.hu>:
>
> * Frederic Weisbecker <fweisbec@...il.com> wrote:
>
>> Impact: use deeper tracing depth safely
>>
>> Some tests showed that function return tracing needed a more deeper depth
>> of function calls. But it could be unsafe to store these return addresses
>> to the stack.
>> So these arrays will now be allocated dynamically into task_struct of current
>> only when the tracer is activated.
>>
>> Typical scheme when tracer is activated:
>> _ allocate a return stack for each task in global list.
>> _ fork: allocate the return stack for the newly created task
>> _ exit: free return stack of current
>> _ idle init: same as fork
>>
>> I chose a default depth of 50. I don't have anymore overruns (didn't tested for
>> a long time).
>>
>> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
>> Cc: Steven Rostedt <rostedt@...dmis.org>
>> ---
>>  arch/x86/include/asm/ftrace.h      |    1 -
>>  arch/x86/include/asm/thread_info.h |   29 -----------
>>  arch/x86/kernel/ftrace.c           |   29 ++++++-----
>>  include/linux/ftrace.h             |    5 ++
>>  include/linux/sched.h              |   23 ++++-----
>>  kernel/exit.c                      |    5 ++-
>>  kernel/fork.c                      |    4 ++
>>  kernel/sched.c                     |    3 +
>>  kernel/trace/ftrace.c              |   96 +++++++++++++++++++++++++++++++++++-
>>  9 files changed, 137 insertions(+), 58 deletions(-)
>
> nice! Applied to tip/tracing/function-return-tracer and i started
> testing it as well.
>
> I've done the small cleanup below on top of your patch - we try to
> avoid #ifdefs in core kernel code as much as possible, by hiding
> .config details into include files.
>
>        Ingo

Ok thanks!
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