* [PATCH v2 27/52] x86, pci, amd-bus: Fix CPU hotplug callback registration [not found] <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> @ 2014-02-14 7:55 ` Srivatsa S. Bhat 2014-02-14 17:35 ` Bjorn Helgaas 0 siblings, 1 reply; 3+ messages in thread From: Srivatsa S. Bhat @ 2014-02-14 7:55 UTC (permalink / raw) To: paulus, oleg, mingo, rusty, peterz, tglx, akpm Cc: paulmck, tj, walken, ego, linux, rjw, linux-kernel, linux-arch, srivatsa.bhat, Bjorn Helgaas, Thomas Gleixner, Ingo Molnar, H. Peter Anvin, x86, linux-pci, Srivatsa S. Bhat Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the amd-bus code in x86 by using this latter form of callback registration. Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-pci@vger.kernel.org Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> --- arch/x86/pci/amd_bus.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/pci/amd_bus.c b/arch/x86/pci/amd_bus.c index a48be98..f05cbf0 100644 --- a/arch/x86/pci/amd_bus.c +++ b/arch/x86/pci/amd_bus.c @@ -380,10 +380,13 @@ static int __init pci_io_ecs_init(void) if (early_pci_allowed()) pci_enable_pci_io_ecs(); - register_cpu_notifier(&amd_cpu_notifier); + cpu_notifier_register_begin(); for_each_online_cpu(cpu) amd_cpu_notify(&amd_cpu_notifier, (unsigned long)CPU_ONLINE, (void *)(long)cpu); + __register_cpu_notifier(&amd_cpu_notifier); + cpu_notifier_register_done(); + pci_probe |= PCI_HAS_IO_ECS; return 0; ^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2 27/52] x86, pci, amd-bus: Fix CPU hotplug callback registration 2014-02-14 7:55 ` [PATCH v2 27/52] x86, pci, amd-bus: Fix CPU hotplug callback registration Srivatsa S. Bhat @ 2014-02-14 17:35 ` Bjorn Helgaas 2014-02-14 18:03 ` Srivatsa S. Bhat 0 siblings, 1 reply; 3+ messages in thread From: Bjorn Helgaas @ 2014-02-14 17:35 UTC (permalink / raw) To: Srivatsa S. Bhat Cc: paulus@samba.org, oleg, Ingo Molnar, Rusty Russell, Peter Zijlstra, Thomas Gleixner, Andrew Morton, Paul McKenney, Tejun Heo, Michel Lespinasse, ego, Russell King, Rafael J. Wysocki, linux-kernel@vger.kernel.org, Linux-Arch, H. Peter Anvin, x86@kernel.org, linux-pci@vger.kernel.org On Fri, Feb 14, 2014 at 12:55 AM, Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> wrote: > Subsystems that want to register CPU hotplug callbacks, as well as perform > initialization for the CPUs that are already online, often do it as shown > below: > > get_online_cpus(); > > for_each_online_cpu(cpu) > init_cpu(cpu); > > register_cpu_notifier(&foobar_cpu_notifier); > > put_online_cpus(); > > This is wrong, since it is prone to ABBA deadlocks involving the > cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently > with CPU hotplug operations). > > Instead, the correct and race-free way of performing the callback > registration is: > > cpu_notifier_register_begin(); > > for_each_online_cpu(cpu) > init_cpu(cpu); > > /* Note the use of the double underscored version of the API */ > __register_cpu_notifier(&foobar_cpu_notifier); > > cpu_notifier_register_done(); > > > Fix the amd-bus code in x86 by using this latter form of callback > registration. > > Cc: Bjorn Helgaas <bhelgaas@google.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: x86@kernel.org > Cc: linux-pci@vger.kernel.org > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> This looks fine to me. Acked-by: Bjorn Helgaas <bhelgaas@google.com> I think it makes sense for you to merge it along with all your other similar changes. I don't foresee any conflicts with things in my PCI tree. > --- > > arch/x86/pci/amd_bus.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/pci/amd_bus.c b/arch/x86/pci/amd_bus.c > index a48be98..f05cbf0 100644 > --- a/arch/x86/pci/amd_bus.c > +++ b/arch/x86/pci/amd_bus.c > @@ -380,10 +380,13 @@ static int __init pci_io_ecs_init(void) > if (early_pci_allowed()) > pci_enable_pci_io_ecs(); > > - register_cpu_notifier(&amd_cpu_notifier); > + cpu_notifier_register_begin(); > for_each_online_cpu(cpu) > amd_cpu_notify(&amd_cpu_notifier, (unsigned long)CPU_ONLINE, > (void *)(long)cpu); > + __register_cpu_notifier(&amd_cpu_notifier); > + cpu_notifier_register_done(); > + > pci_probe |= PCI_HAS_IO_ECS; > > return 0; > ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2 27/52] x86, pci, amd-bus: Fix CPU hotplug callback registration 2014-02-14 17:35 ` Bjorn Helgaas @ 2014-02-14 18:03 ` Srivatsa S. Bhat 0 siblings, 0 replies; 3+ messages in thread From: Srivatsa S. Bhat @ 2014-02-14 18:03 UTC (permalink / raw) To: Bjorn Helgaas Cc: paulus@samba.org, oleg, Ingo Molnar, Rusty Russell, Peter Zijlstra, Thomas Gleixner, Andrew Morton, Paul McKenney, Tejun Heo, Michel Lespinasse, ego, Russell King, Rafael J. Wysocki, linux-kernel@vger.kernel.org, Linux-Arch, H. Peter Anvin, x86@kernel.org, linux-pci@vger.kernel.org On 02/14/2014 11:05 PM, Bjorn Helgaas wrote: > On Fri, Feb 14, 2014 at 12:55 AM, Srivatsa S. Bhat > <srivatsa.bhat@linux.vnet.ibm.com> wrote: >> Subsystems that want to register CPU hotplug callbacks, as well as perform >> initialization for the CPUs that are already online, often do it as shown >> below: >> >> get_online_cpus(); >> >> for_each_online_cpu(cpu) >> init_cpu(cpu); >> >> register_cpu_notifier(&foobar_cpu_notifier); >> >> put_online_cpus(); >> >> This is wrong, since it is prone to ABBA deadlocks involving the >> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently >> with CPU hotplug operations). >> >> Instead, the correct and race-free way of performing the callback >> registration is: >> >> cpu_notifier_register_begin(); >> >> for_each_online_cpu(cpu) >> init_cpu(cpu); >> >> /* Note the use of the double underscored version of the API */ >> __register_cpu_notifier(&foobar_cpu_notifier); >> >> cpu_notifier_register_done(); >> >> >> Fix the amd-bus code in x86 by using this latter form of callback >> registration. >> >> Cc: Bjorn Helgaas <bhelgaas@google.com> >> Cc: Thomas Gleixner <tglx@linutronix.de> >> Cc: Ingo Molnar <mingo@kernel.org> >> Cc: "H. Peter Anvin" <hpa@zytor.com> >> Cc: x86@kernel.org >> Cc: linux-pci@vger.kernel.org >> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> > > This looks fine to me. > > Acked-by: Bjorn Helgaas <bhelgaas@google.com> > > I think it makes sense for you to merge it along with all your other > similar changes. I don't foresee any conflicts with things in my PCI > tree. > Great! Thank you! Regards, Srivatsa S. Bhat ^ permalink raw reply [flat|nested] 3+ messages in thread
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2014-02-14 7:55 ` [PATCH v2 27/52] x86, pci, amd-bus: Fix CPU hotplug callback registration Srivatsa S. Bhat
2014-02-14 17:35 ` Bjorn Helgaas
2014-02-14 18:03 ` Srivatsa S. Bhat
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