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

From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: stian@nixia.no, Blaisorblade <blaisorblade_spam@yahoo.it>,
	"User-mode Linux Kernel Development"
	<user-mode-linux-devel@lists.sourceforge.net>,
	"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 13:15:02 +0100	[thread overview]
Message-ID: <41920646.3090802@fujitsu-siemens.com> (raw)
In-Reply-To: <Pine.GSO.4.61.0411101005310.17015@waterleaf.sonytel.be>

Geert Uytterhoeven wrote:
> 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?
OK. It's an API call. But what's this API call defined to return? Isn't it the
pid of the process calling? If it is, the behavior of the lib is a bug. If it
isn't, the descriptions are wrong. Do you agree?

Bodo


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