Messages in this thread |  | | Date | Tue, 11 Feb 2014 18:15:53 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 01/51] CPU hotplug: Provide lockless versions of callback registration functions |
| |
On 02/11, Srivatsa S. Bhat wrote: > > +static DECLARE_RWSEM(cpu_hotplug_rwsem); > + > +void cpu_notifier_register_begin(void) > +{ > + down_read(&cpu_hotplug_rwsem); > +} > + > +void cpu_notifier_register_end(void) > +{ > + up_read(&cpu_hotplug_rwsem); > +} > + > /* Serializes the updates to cpu_online_mask, cpu_present_mask */ > static DEFINE_MUTEX(cpu_add_remove_lock); > > @@ -32,12 +45,14 @@ static DEFINE_MUTEX(cpu_add_remove_lock); > */ > void cpu_maps_update_begin(void) > { > + down_write(&cpu_hotplug_rwsem); > mutex_lock(&cpu_add_remove_lock); > } > > void cpu_maps_update_done(void) > { > mutex_unlock(&cpu_add_remove_lock); > + up_write(&cpu_hotplug_rwsem); > }
I am a bit confused... If we do this, why we can't simply turn cpu_add_remove_lock into rw_semaphore?
Oleg.
|  |