From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH RFC] acpi: Fix unprotected smp_processor_id() in acpi_processor_cst_has_changed() Date: Tue, 28 Feb 2012 13:27:44 -0800 Message-ID: <20120228212744.GL2465@linux.vnet.ibm.com> References: <20120223205805.GA31838@linux.vnet.ibm.com> <20120228071943.GE1112@zhy> <20120228133013.GE2465@linux.vnet.ibm.com> <201202282157.53804.rjw@sisk.pl> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <201202282157.53804.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" Cc: lenb@kernel.org, Yong Zhang , deepthi@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org List-Id: linux-acpi@vger.kernel.org On Tue, Feb 28, 2012 at 09:57:53PM +0100, Rafael J. Wysocki wrote: > On Tuesday, February 28, 2012, Paul E. McKenney wrote: > > On Tue, Feb 28, 2012 at 03:19:43PM +0800, Yong Zhang wrote: > > > On Thu, Feb 23, 2012 at 12:58:05PM -0800, Paul E. McKenney wrote: > > > > 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 > > > > > > Got the same warning. > > > And the patch works on my side. > > > > > > Tested-by: Yong Zhang > > > > Thank you, I have added your Tested-by (and Srivatsa's Reviewed-by, > > for that matter). > > > > Any takers for this, or should I just push it up the -tip tree? > > I think this patch is for Len, either through ACPI, or through the idle tree. > Len? Whichever way it is supposed to go, it reminds me of the need for it every time I forget to merge it in before testing. ;-) > Anyway: > > Acked-by: Rafael J. Wysocki Thank you, applied! The patch appears below with the recent review, testing, and ack. Thanx, Paul ------------------------------------------------------------------------ acpi: Fix unprotected smp_processor_id() in acpi_processor_cst_has_changed() 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(). Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Reviewed-by: Srivatsa S. Bhat Tested-by: Yong Zhang Acked-by: Rafael J. Wysocki 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 */