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Date: Fri, 9 Sep 2011 09:18:53 +0900
From: Tejun Heo <tj@...nel.org>
To: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
Denys Vlasenko <vda.linux@...glemail.com>
Subject: Re: Why I want PTRACE_O_TRACESTOP option
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. :(
Thanks.
--
tejun
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