From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759135Ab2CNJna (ORCPT ); Wed, 14 Mar 2012 05:43:30 -0400 Received: from casper.infradead.org ([85.118.1.10]:53123 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752585Ab2CNJn3 convert rfc822-to-8bit (ORCPT ); Wed, 14 Mar 2012 05:43:29 -0400 Message-ID: <1331718197.18960.106.camel@twins> Subject: RE: [PATCH] Fix the race between smp_call_function and CPU booting From: Peter Zijlstra To: "Liu, Chuansheng" Cc: "linux-kernel@vger.kernel.org" , Yanmin Zhang , "tglx@linutronix.de" Date: Wed, 14 Mar 2012 10:43:17 +0100 In-Reply-To: <27240C0AC20F114CBF8149A2696CBE4A0556FA@SHSMSX101.ccr.corp.intel.com> References: <27240C0AC20F114CBF8149A2696CBE4A053BE8@SHSMSX101.ccr.corp.intel.com> <1331546307.18960.26.camel@twins> <27240C0AC20F114CBF8149A2696CBE4A054D70@SHSMSX101.ccr.corp.intel.com> <1331654251.18960.78.camel@twins> <27240C0AC20F114CBF8149A2696CBE4A0556FA@SHSMSX101.ccr.corp.intel.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2012-03-14 at 06:27 +0000, Liu, Chuansheng wrote: > On the unplug case, after set the CPU to !active, we do not need IPI > handling for the corresponding > CPU before it is set to offline. I did not find any impact that > limiting the smp_call_function > just after CPU is active. Have a look at Alpha, it's flush_tlb_mm() can use smp_call_function(), in the !active,online case you very much still need to tlb flush that cpu. The fact that it works on a limited use case on x86 doesn't say anything much at all.