From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH RFC] acpi: Fix unprotected smp_processor_id() in acpi_processor_cst_has_changed() Date: Thu, 23 Feb 2012 12:58:05 -0800 Message-ID: <20120223205805.GA31838@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e9.ny.us.ibm.com ([32.97.182.139]:54868 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757015Ab2BWU6Q (ORCPT ); Thu, 23 Feb 2012 15:58:16 -0500 Received: from /spool/local by e9.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 23 Feb 2012 15:58:15 -0500 Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: deepthi@linux.vnet.ibm.com Cc: linux-kernel@vger.kernel.org, lenb@kernel.org, linux-acpi@vger.kernel.org The acpi_processor_cst_has_changed() function is invoked from a CPU_ONLINE or CPU_DEAD function, which might well execute on CPU 0 even though the CPU being hotplugged is some other CPU. In addition, acpi_processor_cst_has_changed() invokes smp_processor_id() without protection, resulting in splats when onlining CPUs. This commit therefore changes the smp_processor_id() to pr->id, as is used elsewhere in the code, for example, in acpi_processor_add(). This works for me, but I don't claim to understand ACPI. Signed-off-by: Paul E. McKenney diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 0e8e2de..9e57b06 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -1159,8 +1159,7 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr) * to make the code that updates C-States be called once. */ - if (smp_processor_id() == 0 && - cpuidle_get_driver() == &acpi_idle_driver) { + if (pr->id == 0 && cpuidle_get_driver() == &acpi_idle_driver) { cpuidle_pause_and_lock(); /* Protect against cpu-hotplug */