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SubjectRE: [patch] x86, perf_counter, bts: add bts to perf_counter
>-----Original Message-----
>From: Peter Zijlstra [mailto:a.p.zijlstra@chello.nl]
>Sent: Friday, August 07, 2009 1:45 PM
>To: Metzger, Markus T
>Cc: linux-kernel@vger.kernel.org; mingo@elte.hu; tglx@linutronix.de; hpa@zytor.com;
>markus.t.metzger@gmail.com; oleg@redhat.com
>Subject: Re: [patch] x86, perf_counter, bts: add bts to perf_counter
>
>On Fri, 2009-08-07 at 09:22 +0200, Markus Metzger wrote:
>> @@ -721,9 +903,13 @@ static int __hw_perf_counter_init(struct
>> err = 0;
>> if (!atomic_inc_not_zero(&active_counters)) {
>> mutex_lock(&pmc_reserve_mutex);
>> - if (atomic_read(&active_counters) == 0 && !reserve_pmc_hardware())
>> - err = -EBUSY;
>> - else
>> + if (atomic_read(&active_counters) == 0) {
>> + if (!reserve_pmc_hardware())
>> + err = -EBUSY;
>> + else
>> + reserve_bts_hardware();
>> + }
>> + if (!err)
>> atomic_inc(&active_counters);
>> mutex_unlock(&pmc_reserve_mutex);
>> }
>
>You loose the reserve_bts_hardware() error case there.


That had been intentional since I consider BTS somewhat optional. In case it is not available or
fails to initialize, e.g. out of memory, we fall back to normal profiling.

Now that I think about it again, I guess that's not what a (debugger) user would expect.
An error might be more appropriate in that case.

I'll change it.

thanks and regards,
markus.

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