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From: David Howells <dhowells@redhat.com>
In-Reply-To: <20081107075003.fa93ccf4.akpm@linux-foundation.org>
References: <20081107075003.fa93ccf4.akpm@linux-foundation.org> <20081107003816.9b0f947a.akpm@linux-foundation.org> <20081107052336.652868737@polymtl.ca> <20081107053349.861709786@polymtl.ca> <20081106220530.5b0e3a96.akpm@linux-foundation.org> <alpine.LFD.2.00.0811070256450.13034@xanadu.home> <25363.1226056819@redhat.com> <alpine.LFD.2.00.0811070952150.13034@xanadu.home> 
To: Andrew Morton <akpm@linux-foundation.org>
Cc: dhowells@redhat.com, Nicolas Pitre <nico@cam.org>,
       Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       linux-kernel@vger.kernel.org, Ralf Baechle <ralf@linux-mips.org>,
       benh@kernel.crashing.org, paulus@samba.org,
       David Miller <davem@davemloft.net>, Ingo Molnar <mingo@redhat.com>,
       Thomas Gleixner <tglx@linutronix.de>,
       Steven Rostedt <rostedt@goodmis.org>, linux-arch@vger.kernel.org
Subject: Re: [RFC patch 08/18] cnt32_to_63 should use smp_rmb()
Date: Fri, 07 Nov 2008 16:21:55 +0000
Message-ID: <8189.1226074915@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1369
Lines: 32

Andrew Morton <akpm@linux-foundation.org> wrote:

> If gcc did that then it would need to generate static instances of
> inlined functions within individual compilation units.  It would be a
> disaster for the kernel.  For a start, functions which are "inlined" in kernel
> modules wouldn't be able to access their static storage and modprobing
> them would fail.

Do you expect a static inline function that lives in a header file and that
has a static variable in it to share that static variable over all instances
of that function in a program?  Or do you expect the static variable to be
limited at the file level?  Or just at the invocation level?

> Does mn10300's get_cycles() really count backwards?

Yes, because the value is generated by a pair of cascaded 16-bit hardware
down-counters.

> The first two callsites I looked at (crypto/tcrypt.c and fs/ext4/mballoc.c)
> assume that it is an upcounter.

Hmmm...  I didn't occur to me that get_cycles() was available for use outside
of arch code.  Possibly it wasn't so used when I first came up with the code.

I should probably make it count the other way.

David
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