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Date: Thu, 16 Sep 2004 12:44:23 +0000 (UTC)
From: Zwane Mwaikambo <zwane@linuxpower.ca>
To: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <ak@suse.de>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org, wli@holomorphy.com
Subject: Re: [PATCH] remove LOCK_SECTION from x86_64 spin_lock asm
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On Thu, 16 Sep 2004, Ingo Molnar wrote:

> the ebp trick is nice, but forcing a formal stack frame for every
> function has global performance implications. Couldnt we define some
> sort of current-> field [or current_thread_info() field] that the
> spinlock code could set and clear, which field would be listened to by
> profile_pc(), so that the time spent spinning would be attributed to the
> callee? Something like:

I think the generic route is nice but wouldn't this break with the 
following.

taskA:
spin_lock(lockA); // contended
<interrupt>
int1:
spin_lock(lockB)

I was thinking along the likes of a per_cpu real_pc, but realised it falls 
prey to the same problem as above... Unless we have irq threads, then of 
course your solution works.

	Zwane

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