Messages in this thread | | | Date | Mon, 16 Jan 2012 13:53:30 +0100 | From | Ingo Molnar <> | Subject | Re: [GIT PULL] tracing: make signal tracepoints more useful |
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* 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
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