linux-kernel - Re: [PATCH 0/7] add syscall tracepoints

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Message-ID: <20090618022102.GA8095@nowhere>
Date:	Thu, 18 Jun 2009 04:21:05 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Jason Baron <jbaron@...hat.com>, linux-kernel@...r.kernel.org,
	laijs@...fujitsu.com, rostedt@...dmis.org, peterz@...radead.org,
	mathieu.desnoyers@...ymtl.ca, jiayingz@...gle.com,
	bligh@...gle.com, roland@...hat.com, fche@...hat.com
Subject: Re: [PATCH 0/7] add syscall tracepoints

On Tue, Jun 16, 2009 at 09:32:20PM +0200, Ingo Molnar wrote:
> 
> * Jason Baron <jbaron@...hat.com> wrote:
> 
> > hi,
> > 
> > The following is an implementation of Frederic's syscall tracer on 
> > top of tracepoints. It adds the ability to toggle the entry/exit 
> > of each syscall via the standard 
> > events/syscalls/syscall_blah/enable interface. The implementation 
> > is done by adding 2 tracepoints. One on entry and one for exit.
> > 
> > This implementation required a few 'core' api changes. I've added 
> > 'DECLARE_TRACE_REG()' macro which takes a register and and an 
> > unregister function as arguments. This allowed me to toggle the 
> > ftrace tif flag when the first tracepoint callback is added and 
> > the last is removed. Current callers of 'DECLARE_TRACE()' are not 
> > impacted.
> > 
> > Another change was to call arch_init_ftrace_syscalls via an 
> > 'arch_initall'. In this implmentation I needed to access the 
> > syscalls_metadata structure at runtime in order to determine which 
> > syscalls were 'traceable'. Although the implementation uses 
> > SYSCALL_DEFINE() to set up the the trace events, for some reason 
> > at runtime there is no syscalls_metadata, associated with some of 
> > the SYSCALL_DEFINE() calls. I'm not quite sure why that is. 
> > However, by calling arch_init_ftrace_syscalls() at boot I can make 
> > sure the lists are in sync.
> > 
> > thanks,
> > 
> > -Jason 
> > 
> > 
> >  arch/x86/include/asm/ftrace.h |    4 +-
> >  arch/x86/kernel/ftrace.c      |   24 +++++-
> >  arch/x86/kernel/ptrace.c      |    6 +-
> >  include/linux/syscalls.h      |   63 +++++++++++++++
> >  include/linux/tracepoint.h    |   27 ++++++-
> >  include/trace/syscall.h       |   37 +++++++---
> >  kernel/trace/trace_events.c   |   29 +++++---
> >  kernel/trace/trace_syscalls.c |  172 +++++++++++++++++++----------------------
> >  kernel/tracepoint.c           |   38 +++++++++
> >  9 files changed, 278 insertions(+), 122 deletions(-)
> 
> This looks far nicer structurally. Steve, Frederic, what's your take 
> on this series?
> 
> 	Ingo


Sorry, I hadn't a lot of time recently to review it but I'll
have some time to do it soon.

Thanks.

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