linux-kernel - Re: [PATCH 1/3] perf events: fix WARN_ON

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Message-ID: <20110218145348.GA302@ghostprotocols.net>
Date:	Fri, 18 Feb 2011 12:53:48 -0200
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	David Ahern <daahern@...co.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	mingo@...e.hu, paulus@...ba.org
Subject: Re: [PATCH 1/3] perf events: fix WARN_ON_ONCE for 64-bit raw data,
 SW events

Em Fri, Feb 18, 2011 at 07:33:28AM -0700, David Ahern escreveu:
> On 02/18/11 04:00, Peter Zijlstra wrote:
> > On Thu, 2011-02-17 at 22:53 -0700, David Ahern wrote:
> >> This check does not work out for 64-bit counter:
> >>
> >>     sizeof(u32) + sizeof(u64) = 4 + 8 = 12
> >>
> >> which does not pass the WARN_ON_ONCE test. I'm guessing (hoping
> >> really) that the intent is that the size of the raw data is a
> >> multiple of 4 bytes, not 8.
> > 
> > No the data must come in 8bytes strides.
> > 
> 
> Then the sizeof the size field needs to be moved to u64; right now it is
> u32:
> 
> struct perf_raw_record {
>     u32             size;
>     void                *data;
> };
> 
> So size should be changed to u64 rather than modifying the WARN_ON_ONCE?

Yeah, I guess so, 32-bit has to die it seems, gets in the way of testing
:-)

- Arnaldo
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