linux-kernel - Re: [PATCH] arm: armv7: perf: fix armv7 ref-cycles error

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Date:	Wed, 8 Oct 2014 20:41:47 -0700
From:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:	zhangzhiqiang <zhangzhiqiang.zhang@...wei.com>
Cc:	Will Deacon <will.deacon@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	"cov@...eaurora.org" <cov@...eaurora.org>,
	"lizefan@...wei.com" <lizefan@...wei.com>,
	"wangnan0@...wei.com" <wangnan0@...wei.com>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] arm: armv7: perf: fix armv7 ref-cycles error

On Thu, Oct 09, 2014 at 11:07:04AM +0800, zhangzhiqiang wrote:
> On 2014/10/8 21:38, Will Deacon wrote:
> > On Wed, Oct 08, 2014 at 02:31:47PM +0100, gregkh@...uxfoundation.org wrote:
> >> On Wed, Oct 08, 2014 at 10:17:41AM +0100, Will Deacon wrote:
> >>> On Wed, Oct 08, 2014 at 04:06:12AM +0100, zhangzhiqiang wrote:
> >>>> hi all,
> >>>> ----------------------------------------
> >>>>
> >>>> ref-cycles event is specially to Intel core, but can still used in arm architecture
> >>>> with the wrong return value with 3.10 stable. for instance:
> >>>>
> >>>>  perf stat -e ref-cycles sleep 1
> >>>>
> >>>>  Performance counter stats for 'sleep 1':
> >>>>
> >>>>   	0 ref-cycles
> >>>>
> >>>>        1.002381916 seconds time elapsed
> >>>>
> >>>> this patch fix the bug and make it return NOT SUPPORTED
> >>>> distinctly.
> >>>>
> >>>> In upstream this bug has been fixed by other way(not primary for the bug), which changes more than one file
> >>>> and more than 1000 lines. the primary commit is 6b7658ec8a100b608e59e3cde353434db51f5be0.
> >>>> besides we can not simply cherry-pick.
> >>>
> >>> I thought I saw Greg pick this up the other day?
> >>
> >> Yes, it's in 3.16.4, did I do something wrong by accepting it?
> > 
> > Nah, it's a trivial patch that I struggle to get excited about. I'm just not
> > sure why it's being sent again, after you already accepted it.
> 
> Yes, it's in 3.16.4, in my opinion 3.10 need it too, can we put it into 3.10 or
> do we have the plan?

Does it apply to 3.10-stable?  Did you test it there and see if it
resolves your issue?

thanks,

greg k-h
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