On Fri, Feb 14, 2014 at 12:55 AM, Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > Cc: x86@xxxxxxxxxx > Cc: linux-pci@xxxxxxxxxxxxxxx > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> This looks fine to me. Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> 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; > -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
