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Subject: Re: [PATCH RESEND 2/2] perf/x86/lbr: Move cpuc->lbr_xsave allocation
 out of sleeping region
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Kan Liang <kan.liang@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>, x86@kernel.org,
        linux-kernel@vger.kernel.org
References: <20210421021825.37872-1-like.xu@linux.intel.com>
 <20210421021825.37872-2-like.xu@linux.intel.com>
 <YH/kikWFlfD260qy@hirez.programming.kicks-ass.net>
From:   Like Xu <like.xu@linux.intel.com>
Organization: Intel OTC
Message-ID: <13fd7ac4-46fd-3fa7-0e80-3f46cfc8edac@linux.intel.com>
Date:   Wed, 21 Apr 2021 16:48:36 +0800
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Hi Peter,

On 2021/4/21 16:38, Peter Zijlstra wrote:
> On Wed, Apr 21, 2021 at 10:18:25AM +0800, Like Xu wrote:
>> -int x86_reserve_hardware(void)
>> +int x86_reserve_hardware(struct perf_event *event)
>>   {
>>   	int err = 0;
>>   
>> @@ -398,8 +398,10 @@ int x86_reserve_hardware(void)
>>   		if (atomic_read(&pmc_refcount) == 0) {
>>   			if (!reserve_pmc_hardware())
>>   				err = -EBUSY;
>> -			else
>> +			else {
>>   				reserve_ds_buffers();
>> +				reserve_lbr_buffers(event);
>> +			}
>>   		}
>>   		if (!err)
>>   			atomic_inc(&pmc_refcount);
>> @@ -650,7 +652,7 @@ static int __x86_pmu_event_init(struct perf_event *event)
>>   	if (!x86_pmu_initialized())
>>   		return -ENODEV;
>>   
>> -	err = x86_reserve_hardware();
>> +	err = x86_reserve_hardware(event);
>>   	if (err)
>>   		return err;
>>   
> 
> This is still complete garbage..

Hhh,thanks for your comment!

So do we have a better idea to alloc cpuc->lbr_xsave
to avoid this kind of call trace ?

>