Il 14/02/2014 08:55, Srivatsa S. Bhat ha scritto:
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 kvm code in x86 by using this latter form of callback registration. Cc: Gleb Natapov <g...@kernel.org> Cc: Paolo Bonzini <pbonz...@redhat.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Ingo Molnar <mi...@kernel.org> Cc: "H. Peter Anvin" <h...@zytor.com> Cc: x...@kernel.org Cc: k...@vger.kernel.org Signed-off-by: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com> --- arch/x86/kvm/x86.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 39c28f09..0166923 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5365,7 +5365,8 @@ static void kvm_timer_init(void) int cpu; max_tsc_khz = tsc_khz; - register_hotcpu_notifier(&kvmclock_cpu_notifier_block); + + cpu_notifier_register_begin(); if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) { #ifdef CONFIG_CPU_FREQ struct cpufreq_policy policy; @@ -5382,6 +5383,10 @@ static void kvm_timer_init(void) pr_debug("kvm: max_tsc_khz = %ld\n", max_tsc_khz); for_each_online_cpu(cpu) smp_call_function_single(cpu, tsc_khz_changed, NULL, 1); + + __register_hotcpu_notifier(&kvmclock_cpu_notifier_block); + cpu_notifier_register_done(); + } static DEFINE_PER_CPU(struct kvm_vcpu *, current_vcpu);
Acked-by: Paolo Bonzini <pbonz...@redhat.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
