| Message ID | 20140205221122.19080.64763.stgit@srivatsabhat.in.ibm.com (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
On Thursday, February 06, 2014 03:41:23 AM Srivatsa S. Bhat 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_maps_update_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_maps_update_done(); > > > Fix the intel-idle code by using this latter form of callback registration. > > Cc: Len Brown <lenb@kernel.org> > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> > Cc: linux-pm@vger.kernel.org > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> This looks good to me. Len, what do you think? Srivatsa, how does it depend on the rest of your series? > --- > > drivers/idle/intel_idle.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c > index 8e1939f..716ee5a 100644 > --- a/drivers/idle/intel_idle.c > +++ b/drivers/idle/intel_idle.c > @@ -681,14 +681,19 @@ static int __init intel_idle_init(void) > if (intel_idle_cpuidle_devices == NULL) > return -ENOMEM; > > + cpu_maps_update_begin(); > + > for_each_online_cpu(i) { > retval = intel_idle_cpu_init(i); > if (retval) { > + cpu_maps_update_done(); > cpuidle_unregister_driver(&intel_idle_driver); > return retval; > } > } > - register_cpu_notifier(&cpu_hotplug_notifier); > + __register_cpu_notifier(&cpu_hotplug_notifier); > + > + cpu_maps_update_done(); > > return 0; > } > @@ -698,10 +703,13 @@ static void __exit intel_idle_exit(void) > intel_idle_cpuidle_devices_uninit(); > cpuidle_unregister_driver(&intel_idle_driver); > > + cpu_maps_update_begin(); > > if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE) > on_each_cpu(__setup_broadcast_timer, (void *)false, 1); > - unregister_cpu_notifier(&cpu_hotplug_notifier); > + __unregister_cpu_notifier(&cpu_hotplug_notifier); > + > + cpu_maps_update_done(); > > return; > } > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
On 02/06/2014 06:13 PM, Rafael J. Wysocki wrote: > On Thursday, February 06, 2014 03:41:23 AM Srivatsa S. Bhat 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_maps_update_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_maps_update_done(); >> >> >> Fix the intel-idle code by using this latter form of callback registration. >> >> Cc: Len Brown <lenb@kernel.org> >> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> >> Cc: linux-pm@vger.kernel.org >> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> > > This looks good to me. Len, what do you think? > Thanks a lot Rafael! > Srivatsa, how does it depend on the rest of your series? > It depends only on the first patch in the series: http://article.gmane.org/gmane.linux.kernel/1641640 But don't take this patch yet, we are discussing a possible rename of the function cpu_maps_update_begin()/done(). So I'll post a v2 after the name is finalized. Thank you! Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index 8e1939f..716ee5a 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -681,14 +681,19 @@ static int __init intel_idle_init(void) if (intel_idle_cpuidle_devices == NULL) return -ENOMEM; + cpu_maps_update_begin(); + for_each_online_cpu(i) { retval = intel_idle_cpu_init(i); if (retval) { + cpu_maps_update_done(); cpuidle_unregister_driver(&intel_idle_driver); return retval; } } - register_cpu_notifier(&cpu_hotplug_notifier); + __register_cpu_notifier(&cpu_hotplug_notifier); + + cpu_maps_update_done(); return 0; } @@ -698,10 +703,13 @@ static void __exit intel_idle_exit(void) intel_idle_cpuidle_devices_uninit(); cpuidle_unregister_driver(&intel_idle_driver); + cpu_maps_update_begin(); if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE) on_each_cpu(__setup_broadcast_timer, (void *)false, 1); - unregister_cpu_notifier(&cpu_hotplug_notifier); + __unregister_cpu_notifier(&cpu_hotplug_notifier); + + cpu_maps_update_done(); return; }
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_maps_update_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_maps_update_done(); Fix the intel-idle code by using this latter form of callback registration. Cc: Len Brown <lenb@kernel.org> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: linux-pm@vger.kernel.org Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> --- drivers/idle/intel_idle.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html