| Message ID | 20140214075122.22701.18462.stgit@srivatsabhat.in.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Il 14/02/2014 08:51, 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 arm by using this latter form of callback registration. > > Cc: Christoffer Dall <christoffer.dall@linaro.org> > Cc: Gleb Natapov <gleb@kernel.org> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Russell King <linux@arm.linux.org.uk> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: kvmarm@lists.cs.columbia.edu > Cc: kvm@vger.kernel.org > Cc: linux-arm-kernel@lists.infradead.org > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> > --- > > arch/arm/kvm/arm.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > index 1d8248e..147b917 100644 > --- a/arch/arm/kvm/arm.c > +++ b/arch/arm/kvm/arm.c > @@ -1050,21 +1050,26 @@ int kvm_arch_init(void *opaque) > } > } > > + cpu_notifier_register_begin(); > + > err = init_hyp_mode(); > if (err) > goto out_err; > > - err = register_cpu_notifier(&hyp_init_cpu_nb); > + err = __register_cpu_notifier(&hyp_init_cpu_nb); > if (err) { > kvm_err("Cannot register HYP init CPU notifier (%d)\n", err); > goto out_err; > } > > + cpu_notifier_register_done(); > + > hyp_cpu_pm_init(); > > kvm_coproc_table_init(); > return 0; > out_err: > + cpu_notifier_register_done(); > return err; > } > > Acked-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c index 1d8248e..147b917 100644 --- a/arch/arm/kvm/arm.c +++ b/arch/arm/kvm/arm.c @@ -1050,21 +1050,26 @@ int kvm_arch_init(void *opaque) } } + cpu_notifier_register_begin(); + err = init_hyp_mode(); if (err) goto out_err; - err = register_cpu_notifier(&hyp_init_cpu_nb); + err = __register_cpu_notifier(&hyp_init_cpu_nb); if (err) { kvm_err("Cannot register HYP init CPU notifier (%d)\n", err); goto out_err; } + cpu_notifier_register_done(); + hyp_cpu_pm_init(); kvm_coproc_table_init(); return 0; out_err: + cpu_notifier_register_done(); return err; }
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 arm by using this latter form of callback registration. Cc: Christoffer Dall <christoffer.dall@linaro.org> Cc: Gleb Natapov <gleb@kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: Ingo Molnar <mingo@kernel.org> Cc: kvmarm@lists.cs.columbia.edu Cc: kvm@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> --- arch/arm/kvm/arm.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)