From: Ingo Molnar <mingo@elte.hu>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@redhat.com>,
Masami Hiramatsu <mhiramat@redhat.com>,
Seiji Aguchi <saguchi@redhat.com>,
linux-kernel@vger.kernel.org,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Subject: Re: [GIT PULL] tracing: make signal tracepoints more useful
Date: Mon, 16 Jan 2012 13:53:30 +0100 [thread overview]
Message-ID: <20120116125329.GB31667@elte.hu> (raw)
In-Reply-To: <1326717070.7642.144.camel@gandalf.stny.rr.com>
* Steven Rostedt <rostedt@goodmis.org> wrote:
> On Mon, 2012-01-16 at 08:45 +0100, Ingo Molnar wrote:
>
> > Looks good to me at a first (quick) sight, except this bit
> > which changes the ABI:
> >
> > > > - TP_printk("sig=%d errno=%d code=%d comm=%s pid=%d",
> > > > + TP_printk("sig=%d errno=%d code=%d comm=%s pid=%d grp=%d res=%d",
> >
> > That's not how we change tracepoints generally - we add a new
> > one and eventually phase out the old one. Which apps/tools rely
> > on the old tracepoint? If it's exactly zero apps then we might
> > be able to change it, but this needs to be investigated.
>
> But this tracepoint wasn't changed, it was added on to.
> There's a difference. Any tool that uses this (including
> something like powertop) should be able to handle it. [...]
That's mostly true in theory - the question is, is it true in
practice?
Say if an app relies on the smaller data structure, it sure
might get surprised by the kernel writing a wider record ...
Thanks,
Ingo
next prev parent reply other threads:[~2012-01-16 12:53 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-10 17:45 [PATCH 0/2] " Oleg Nesterov
2012-01-10 17:45 ` [PATCH 1/2] tracing: let trace_signal_generate() report more info, kill overflow_fail/lose_info Oleg Nesterov
2012-01-10 17:45 ` [PATCH 2/2] tracing: send_sigqueue() needs trace_signal_generate() too Oleg Nesterov
2012-01-10 18:59 ` [PATCH 0/2] tracing: make signal tracepoints more useful Steven Rostedt
2012-01-10 21:09 ` Seiji Aguchi
2012-01-13 18:20 ` [GIT PULL] " Oleg Nesterov
2012-01-15 18:24 ` Oleg Nesterov
2012-01-16 7:45 ` Ingo Molnar
2012-01-16 12:31 ` Steven Rostedt
2012-01-16 12:53 ` Ingo Molnar [this message]
2012-01-16 15:10 ` Oleg Nesterov
2012-01-17 18:50 ` Linus Torvalds
2012-01-18 9:39 ` Ingo Molnar
2012-01-16 15:52 ` Steven Rostedt
2012-01-17 10:02 ` Ingo Molnar
2012-01-17 12:03 ` Steven Rostedt
2012-01-17 12:40 ` Ingo Molnar
2012-01-17 14:04 ` Oleg Nesterov
2012-01-18 11:59 ` Ingo Molnar
2012-01-17 14:37 ` Steven Rostedt
2012-01-17 14:55 ` Oleg Nesterov
2012-01-20 18:01 ` Jason Baron
2012-01-17 19:52 ` Steven Rostedt
2012-01-16 15:03 ` Oleg Nesterov
2012-01-16 15:42 ` Seiji Aguchi
2012-01-16 15:58 ` Steven Rostedt
2012-01-26 10:10 ` Ingo Molnar
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