linux-kernel - Re: [GIT PULL] perf changes for v3.8

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: <CA+55aFzmDooC3tYzvP1YGv9g4ej1hBUQBPV6R+ukrfxuEELBaQ@mail.gmail.com>
Date:	Thu, 13 Dec 2012 08:03:58 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Ahern <dsahern@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] perf changes for v3.8

On Thu, Dec 13, 2012 at 6:30 AM, David Ahern <dsahern@...il.com> wrote:
>
> One of the problems is that existing binaries set the exclude_guest flag
> (https://lkml.org/lkml/2012/7/9/292).

[ to zero ]

Yeah. And it apparently *never* worked. So it's not a regression.

> So, requesting users to update their binaries if they want to use precise
> sampling is not acceptable. A 100% catastrophic failure of all running VMs
> is acceptable? All VMs will crash and there is no direct causal
> relationship.

So instead, you expect everybody else - for whom things *used* to work
- to upgrade their binary, or their scripts, or just start using an
insane command line flag that makes no sense for them? Forcing
non-virtualization users to use a "only trace the host" flag is crazy.

Either way, somebody will be unhappy. No question about that. But our
rule in the kernel is "no regressions".

Now, I do agree that for "perf", it's fairly easy to say "just
recompile". I can do it in seconds, and it would presumably solve my
problem by just making the "host only" case the default, and I don't
need the "H" any more.

But that whole "no regressions" really is important. I can work around
things very easily, but the "no regressions" rule really means that I
should never *need* to work around things.

So when I see a regression, I consider it a major bug, even if the
workaround is trivial.

                     Linus
--
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/