[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <4AA5AA0F.4060104@cn.fujitsu.com>
Date: Tue, 08 Sep 2009 08:49:19 +0800
From: Li Zefan <lizf@...fujitsu.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Tom Zanussi <tzanussi@...il.com>,
Jason Baron <jbaron@...hat.com>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/6] perf_counter: Add PERF_COUNTER_IOC_SET_FILTER ioctl
Peter Zijlstra wrote:
> On Mon, 2009-09-07 at 18:48 +0200, Ingo Molnar wrote:
>> * Peter Zijlstra <peterz@...radead.org> wrote:
>>
>>> On Mon, 2009-09-07 at 16:13 +0800, Li Zefan wrote:
>>>> Allow to set profile filter via ioctl.
>>> Hrm,.. not at all sure about this.. what are the ABI implications?
>> I think the ABI should be fine if it's always a sub-set of C syntax.
>> That would be C expressions initially. Hm?
>
> Right, so I've no clue what filter expressions look like, and the
> changelog doesn't help us at all. It doesn't mention its a well
> considered decision to henceforth freeze the expression syntax.
>
> Of course, since filters so far only work with tracepoint things, and
> since you can only come by tracepoint things through debugfs, and since
> anything debugfs is basically a free-for-all ABI-less world, we might be
> good, but then this is a very ill-defined ioctl() indeed.
>
> So please, consider this well -- there might not be a second chance.
>
Ok, the expressions are:
1. S = opr1 op opr2 (op: ==, !=, <, <=, >, >=.
opr1 should be a field in the format file)
2. E = S1 op S2 (op: ||, &&)
3. E = E1 op E2 (op: ||, &&)
4. () can be used
I don't the syntax will be changed, but we may extend it, like
adding not ! operator. Like, for a func ptr, besides "func==0xccee4400",
we may want to allow "func==foo". Those extentions are ok for the
ABI, right?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists