On Mon, 31 Jan 2022 10:04:16 -0800 Suren Baghdasaryan wrote:
> On Sat, Jan 29, 2022 at 4:13 AM Hillf Danton wrote:
> >
> > On Fri, 28 Jan 2022 05:09:53 -0800 Michel Lespinasse wrote:
> > > +
> > > +static LIST_HEAD(destroy_list);
> > > +static DEFINE_SPINLOCK(destroy_list_lock);
> >
> > static bool destroyer_running;
> >
> > > +
> > > +static void destroy_list_workfn(struct work_struct *work)
> > > +{
> > > + struct percpu_rw_semaphore *sem, *sem2;
> > > + LIST_HEAD(to_destroy);
> > > +
> >
> > again:
> >
> > > + spin_lock(&destroy_list_lock);
> >
> > if (list_empty(&destroy_list)) {
> > destroyer_running = false;
> > spin_unlock(&destroy_list_lock);
> > return;
> > }
> > destroyer_running = true;
> >
> > > + list_splice_init(&destroy_list, &to_destroy);
> > > + spin_unlock(&destroy_list_lock);
> > > +
> > > + if (list_empty(&to_destroy))
> > > + return;
> > > +
> > > + list_for_each_entry_safe(sem, sem2, &to_destroy, destroy_list_entry) {
> >
> > list_del(&sem->destroy_list_entry);
> >
> > > + percpu_free_rwsem(sem);
> > > + kfree(sem);
> > > + }
> >
> > goto again;
> > > +}
> > > +
> > > +static DECLARE_WORK(destroy_list_work, destroy_list_workfn);
> > > +
> > > +void percpu_rwsem_async_destroy(struct percpu_rw_semaphore *sem)
> > > +{
> > > + spin_lock(&destroy_list_lock);
> > > + list_add_tail(&sem->destroy_list_entry, &destroy_list);
> > > + spin_unlock(&destroy_list_lock);
> > > + schedule_work(&destroy_list_work);
> >
> > Nits
> > spin_lock(&destroy_list_lock);
> > 1/ /* LIFO */
> > list_add(&sem->destroy_list_entry, &destroy_list);
> > 2/ /* spawn worker if it is idle */
> > if (!destroyer_running)
> > 3/ /* this is not critical work */
> > queue_work(system_unbound_wq, &destroy_list_work);
> > spin_unlock(&destroy_list_lock);
>
> Thanks for the review! Just to clarify, are you suggesting
> simplifications to the current patch or do you see a function issue?
Apart from the nits that can be safely ignored in usual spins, I wonder if
the async destroy can be used in the contexts wrt raw_spin_lock.
Hillf
raw_spin_lock_irq(&foo->lock);
...
percpu_rwsem_async_destroy(*sem);
...
raw_spin_unlock_irq(&foo->lock);
