Message-ID: <4B01C95B.1070302@redhat.com>
Date: Mon, 16 Nov 2009 16:51:23 -0500
From: Masami Hiramatsu <mhiramat@redhat.com>
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To: Ingo Molnar <mingo@elte.hu>
CC: Roland McGrath <roland@redhat.com>, lkml <linux-kernel@vger.kernel.org>,
       systemtap <systemtap@sources.redhat.com>,
       DLE <dle-develop@lists.sourceforge.net>
Subject: Re: [PATCH -tip 3/3] Add get_signal tracepoint
References: <20091113225226.15079.90813.stgit@harusame> <20091113225240.15079.4863.stgit@harusame> <20091113235333.0E3CC15E8@magilla.sf.frob.com> <20091114001020.GB24738@elte.hu>
In-Reply-To: <20091114001020.GB24738@elte.hu>
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Ingo Molnar wrote:
>> Especially if you call this "get" rather than "deliver", there is
>> another place that should invoke this tracepoint (or perhaps a third
>> one).  sys_rt_sigtimedwait "gets" a signal without delivering it.  In
>> POSIX terminology this is called "accepting" the signal: the three
>> things that can happen in the life of a signal are "generate",
>> "deliver", and "accept".  If you are trying to match up what happened
>> to a signal generated by kill() or whatnot, then you want to notice
>> both delivery and acceptance as the complementary event.
>>
>> (And again I have no clue why this signal stuff should be called
>> "sched" at all.)
>
> it shouldnt be called 'sched' - it should go into 'events/signal.h'.
>
> But we also need fuller coverage than this. Coredumps and signal
> delivery events are just a small part of all things signals, we also
> want:

That's a good idea. I'll put coredump and signal related events
into events/signal.h.

>
>   - signal generation events (send_sig*() variants)

Those events finally calls __send_signal(), so I think
trace_signal_send() can trace those events.

>   - signal IPI/wakeup events

All signals might be used for IPI, isn't it? :-)
Or, did you mean SIGSTOP/SIGCONT pare?

>   - signal loss events (queue overflow)

Perhaps, this event is only for rt-signals, since
legacy signals just overwritten if it was sent.

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com

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