linux-kernel - Re: perf: PERF_EVENT_IOC_PERIOD on ARM vs everywhere else

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20131029134536.GD16117@laptop.programming.kicks-ass.net>
Date:	Tue, 29 Oct 2013 14:45:36 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Will Deacon <will.deacon@....com>
Cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: perf: PERF_EVENT_IOC_PERIOD on ARM vs everywhere else

On Tue, Oct 29, 2013 at 04:28:10AM +0000, Will Deacon wrote:
> On Mon, Oct 28, 2013 at 02:07:48PM +0000, Vince Weaver wrote:
> > It's also a shame this change apprently didn't hit the linux-kernel list 
> > as far as I can tell.  I do my best to try to note all of the perf 
> > ABI-related changes there, but if things like this are going to start 
> > getting merged in architecture trees then things get that much harder 
> > to keep track of.
> 
> I can CC LKML on ARM perf patches if you think it will help, but all PMU
> backend patches go via their respective arch trees afaict.

Just those that change user visible semantics that are shared between
archs I suppose :-)

> > > I don't want to be the `oddball' architecture (at least, not more than I am
> > > already :), but I do find it tricky to follow the required semantics of perf
> > > as opposed to `it happens to work this way', especially when so much of it
> > > is buried in the various arch backends. So if somebody using the thing on
> > > ARM has (what looks to me like) a valid issue, then I usually try and fix
> > > it.
> > 
> > But it was global behavior that was common on all architectures.
> > 
> > Now any cross-platform tool like PAPI is going to have to have a mess of 
> > #ifdefs around every use of this ioctl, and it will only get worse if 
> > other architectures decide to "fix" the problem too.
> 
> What would you like me to do to fix this for you? Moving more code out of
> the backends and into the core will help maintain consistency between
> architectures, but that's a huge job.

We could start by making all archs do the same thing again; but yes
ideally we'd move some of it into generic code. Not entirely sure how
that will work out though, there's a reason its in per-arch code :/


Vince, what would you prefer to do here?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/