Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933398Ab1CZANq (ORCPT ); Fri, 25 Mar 2011 20:13:46 -0400 Received: from kroah.org ([198.145.64.141]:35810 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933189Ab1CZAGQ (ORCPT ); Fri, 25 Mar 2011 20:06:16 -0400 X-Mailbox-Line: From gregkh@clark.kroah.org Fri Mar 25 17:04:56 2011 Message-Id: <20110326000456.346395018@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Fri, 25 Mar 2011 17:03:37 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Michael Neuling , Benjamin Herrenschmidt Subject: [05/35] powerpc/kdump: Fix race in kdump shutdown In-Reply-To: <20110326000509.GA29736@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2673 Lines: 85 2.6.33-longterm review patch. If anyone has any objections, please let us know. ------------------ From: Michael Neuling commit 60adec6226bbcf061d4c2d10944fced209d1847d upstream. When we are crashing, the crashing/primary CPU IPIs the secondaries to turn off IRQs, go into real mode and wait in kexec_wait. While this is happening, the primary tears down all the MMU maps. Unfortunately the primary doesn't check to make sure the secondaries have entered real mode before doing this. On PHYP machines, the secondaries can take a long time shutting down the IRQ controller as RTAS calls are need. These RTAS calls need to be serialised which resilts in the secondaries contending in lock_rtas() and hence taking a long time to shut down. We've hit this on large POWER7 machines, where some secondaries are still waiting in lock_rtas(), when the primary tears down the HPTEs. This patch makes sure all secondaries are in real mode before the primary tears down the MMU. It uses the new kexec_state entry in the paca. It times out if the secondaries don't reach real mode after 10sec. Signed-off-by: Michael Neuling Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/crash.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) --- a/arch/powerpc/kernel/crash.c +++ b/arch/powerpc/kernel/crash.c @@ -162,6 +162,32 @@ static void crash_kexec_prepare_cpus(int /* Leave the IPI callback set */ } +/* wait for all the CPUs to hit real mode but timeout if they don't come in */ +static void crash_kexec_wait_realmode(int cpu) +{ + unsigned int msecs; + int i; + + msecs = 10000; + for (i=0; i < NR_CPUS && msecs > 0; i++) { + if (i == cpu) + continue; + + while (paca[i].kexec_state < KEXEC_STATE_REAL_MODE) { + barrier(); + if (!cpu_possible(i)) { + break; + } + if (!cpu_online(i)) { + break; + } + msecs--; + mdelay(1); + } + } + mb(); +} + /* * This function will be called by secondary cpus or by kexec cpu * if soft-reset is activated to stop some CPUs. @@ -419,6 +445,7 @@ void default_machine_crash_shutdown(stru crash_kexec_prepare_cpus(crashing_cpu); cpu_set(crashing_cpu, cpus_in_crash); crash_kexec_stop_spus(); + crash_kexec_wait_realmode(crashing_cpu); if (ppc_md.kexec_cpu_down) ppc_md.kexec_cpu_down(1, 0); } -- 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/