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	 <87ljg1fn3u.fsf@basil.nowhere.org>
Date: Wed, 13 Jan 2010 18:21:20 -0800
Message-ID: <bc915a051001131821x6cdd3470lf72e8c02a897ea3@mail.gmail.com>
Subject: Re: HW breakpoints perf_events request
From: Joshua Pincus <joshua.pincus@gmail.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
       "K.Prasad" <prasad@linux.vnet.ibm.com>, peterz@infradead.org,
       paulus@samba.org, acme@redhat.com, linux-kernel@vger.kernel.org
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Hi,

On Wed, Jan 13, 2010 at 6:15 PM, Andi Kleen <andi@firstfloor.org> wrote:
> Joshua Pincus <joshua.pincus@gmail.com> writes:
>
>> I have a request for an additional feature to be included
>> in the recent hardware breakpoints work soon to be delivered
>> in kernel 2.6.33.
>
> Sounds to me like the existing ptrace based interface
> can practically all you want
>
> (except that the "parent signal" would be wait and for
> fork/exec you have to explicitely attach)

We would like to avoid using ptrace at all costs.
It requires us to have a parent thread running
which monitors all the others.  It's not clear that
the wait() call by the parent doesn't mask a barrage
of signals from various threads and the performance
penalty is huge in multi-threaded apps.

If we could get this functionality working w/o ptrace,
we'd be very, very happy and grateful.

>
> -Andi
>

Thanks,
JP
--
On Wed, Jan 13, 2010 at 6:15 PM, Andi Kleen <andi@firstfloor.org> wrote:
> Joshua Pincus <joshua.pincus@gmail.com> writes:
>
>> I have a request for an additional feature to be included
>> in the recent hardware breakpoints work soon to be delivered
>> in kernel 2.6.33.
>
> Sounds to me like the existing ptrace based interface
> can practically all you want
>
> (except that the "parent signal" would be wait and for
> fork/exec you have to explicitely attach)
>
> -Andi
>
> --
> ak@linux.intel.com -- Speaking for myself only.
>
--
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