Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755846AbbESJXD (ORCPT ); Tue, 19 May 2015 05:23:03 -0400 Received: from mail-wg0-f44.google.com ([74.125.82.44]:36383 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932241AbbESJNY (ORCPT ); Tue, 19 May 2015 05:13:24 -0400 Date: Tue, 19 May 2015 10:13:18 +0100 From: Matt Fleming To: Thomas Gleixner Cc: LKML , Peter Zijlstra , Vikas Shivappa , x86@kernel.org, Matt Fleming , Will Auld , Kanaka Juvva Subject: Re: [patch 3/6] x86, perf, cqm: Remove pointless spinlock from state cache Message-ID: <20150519091318.GB17401@codeblueprint.co.uk> References: <20150518234114.574556332@linutronix.de> <20150518235150.001006529@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150518235150.001006529@linutronix.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1275 Lines: 32 On Tue, 19 May, at 12:00:53AM, Thomas Gleixner wrote: > struct intel_cqm_state is a strict per cpu cache of the rmid and the > usage counter. It can never be modified from a remote cpu. > > The 3 functions which modify the content: start, stop and del (del > maps to stop) are called from the perf core with interrupts disabled > which is enough protection for the per cpu state values. > > Signed-off-by: Thomas Gleixner > --- > arch/x86/kernel/cpu/perf_event_intel_cqm.c | 17 ++++++----------- > 1 file changed, 6 insertions(+), 11 deletions(-) The state locking code was taken from Peter's original patch last year, so it would be good for him to chime in that this is safe. It's probably just that it was necessary in Peter's patches but after I refactored bits I forgot to rip it out. But yeah, from reading the code again the lock does look entirely superfluous. So unless Peter complains, Acked-by: Matt Fleming -- Matt Fleming, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/