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Date: Thu, 13 Jul 2006 01:33:13 +0400
From: Michael Tokarev <mjt@tls.msk.ru>
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To: "Eric W. Biederman" <ebiederm@xmission.com>
CC: "H. Peter Anvin" <hpa@zytor.com>, Jakub Jelinek <jakub@redhat.com>,
       Ulrich Drepper <drepper@redhat.com>, Roland McGrath <roland@redhat.com>,
       Arjan van de Ven <arjan@infradead.org>,
       "Randy.Dunlap" <rdunlap@xenotime.net>, akpm@osdl.org,
       linux-kernel@vger.kernel.org, libc-alpha@sourceware.org
Subject: Re: [PATCH] Use uname not sysctl to get the kernel revision
References: <20060712184412.2BD57180061@magilla.sf.frob.com>	<44B54EA4.5060506@redhat.com>	<20060712195349.GW3823@sunsite.mff.cuni.cz>	<44B556E5.5000702@zytor.com> <m1k66i8ql5.fsf@ebiederm.dsl.xmission.com>
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Eric W. Biederman wrote:
[]
> Glibc just wants to know if our kernel is SMP so it can know if it is
> ok to busy wait for a bit waiting for a mutex.  Or if busy waiting is
> a complete loss.

BTW, with smp-alternatives thing merged, "SMP or not" may not be that
simple question anymore.

I for one stopped compiling UP and SMP kernels for x86 since 2.6.17,
because SMP kernel works just fine on UP, including benchmarks (as
opposed to SMP kernel w/o smp-alternatives).  But I don't remember
if uname shows SMP in this case or not (don't have any running UP
machine with that kernel right now).

But the thing is: smp-alternatives + cpu-hotplug changes things at
runtime...

/mjt