linux-kernel - Re: perf: multiple mmap of fd behavior on x86/ARM

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Message-ID: <alpine.DEB.2.20.1708111457280.3766@macbook-air>
Date:   Fri, 11 Aug 2017 15:01:43 -0400 (EDT)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Mark Rutland <mark.rutland@....com>
cc:     linux-kernel@...r.kernel.org, Will Deacon <will.deacon@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: perf: multiple mmap of fd behavior on x86/ARM

On Fri, 11 Aug 2017, Mark Rutland wrote:

> > This isn't some key thing that needs to be fixed, I was just curious about 
> > the behavior difference between x86 and ARM. 
> 
> Sure; likewise I'm curious.

well I finally got a current git 64-bit kernel booted on the pi3.

Challenge: USB known to be broken currently, so no keyboard or ethernet.
Extra challenge: had the RX/TX lines switched on the serial connector.
Bonus challenge: the bcm2837 dts file doesn't enable armv8 PMU

I got through all of that, only to find:

$ uname -a
Linux pi3-git 4.13.0-rc4-00152-g2627393 #2 SMP PREEMPT Fri Aug 11 13:58:42 EDT 2017 aarch64 GNU/Linux

$ ./mmap_multiple 
Trying to mmap same perf_event fd multiple times...        PASSED

So maybe the issue was fixed between 4.9 and current?

Vince