Re: [uml-devel] Re: Stop at startup on 2.6 NPTL hosts

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: stian@nixia.no
Cc: Blaisorblade <blaisorblade_spam@yahoo.it>,
	"User-mode Linux Kernel Development"
	<user-mode-linux-devel@lists.sourceforge.net>,
	"Bodo Stroesser" <bstroesser@fujitsu-siemens.com>,
	"Jeff Dike" <jdike@addtoit.com>,
	"Roland Kaeser" <roli8200@yahoo.de>,
	"Nuno Silva" <nuno.silva@vgertech.com>,
	"Antoine Martin" <antoine@nagafix.co.uk>,
	"Sven K�hler" <skoehler@upb.de>,
	"Dennis Muhlestein" <devel@muhlesteins.com>
Subject: Re: [uml-devel] Re: Stop at startup on 2.6 NPTL hosts
Date: Wed, 10 Nov 2004 10:07:09 +0100 (MET)	[thread overview]
Message-ID: <Pine.GSO.4.61.0411101005310.17015@waterleaf.sonytel.be> (raw)
In-Reply-To: <34658.80.203.1.124.1100075791.squirrel@80.203.1.124>

On Wed, 10 Nov 2004 stian@nixia.no wrote:
> > This fact (glibc caches getpid() results) was even known because already
> > posted, and I guessed that this could happen only with TLS support.
> 
> That glibc caches getpid() has been a known issue before when people
> wanted to benchmark uml syscall speeds inside vs outside of UML using a
> simple libc-function. A clone() call can't easily invalidate caches around
> in libs that are stored in statics. But it should be mentioned on
> getpid()'s man/info page that the value might be cached.

Why? getpid() is just an API call. No one guarantees it's actually a syscall.
And IMHO caching getpid() is allowed, since the returned value won't change
anyway.

If you want to be 100% sure you use a syscall, why not call the syscall
directly?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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