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> --- 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-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
