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Date: Fri, 9 Sep 2011 07:45:35 +0200
From: Denys Vlasenko <vda.linux@...glemail.com>
To: Tejun Heo <tj@...nel.org>
Cc: Denys Vlasenko <dvlasenk@...hat.com>,
Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: Why I want PTRACE_O_TRACESTOP option
On Friday 09 September 2011 02:18, Tejun Heo wrote:
> Hello, Denys.
>
> On Thu, Sep 08, 2011 at 06:50:01PM +0200, Denys Vlasenko wrote:
> > Consider what will happen when a next ptrace fix will require
> > a way to change ptrace API at runtime. A new option will likely
> > be introduced, say, PTRACE_O_TRACEPONY, with next available
> > bit position 7, and perhaps some new event will be generated,
> > PTRACE_EVENT_PONY, with value.... yes, it can't be 7,
> > PTRACE_EVENT_STOP took it. So it will probably be 8.
>
> Then, just give it the next matching number.
>
> If options naturally happen to match the events, that's a nice
> coincidence. If the real life requirement deviates from the beautiful
> one-to-one mapping, then, so be it. No, the magical contiguous one to
> one mapping isn't the most important design concern.
>
> To me, the rationale presented here almost argues against
> PTRACE_O_TRACESTOP. :(
How about changing PTRACE_EVENT_STOP value to, say, 255 then,
in order to move it away from (option,event) area?
--
vda
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