Messages in this thread | | | Date | Wed, 20 Jan 2021 20:45:54 +0100 | From | Sebastian Andrzej Siewior <> | Subject | Re: [PATCH 3/3] kvfree_rcu: use migrate_disable/enable() |
| |
On 2021-01-20 17:21:48 [+0100], Uladzislau Rezki (Sony) wrote: > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -3489,10 +3489,12 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp, > (*krcp)->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) { > bnode = get_cached_bnode(*krcp); > if (!bnode && can_alloc) { > + migrate_disable(); > krc_this_cpu_unlock(*krcp, *flags);
Why is krc_this_cpu_unlock() defined as | static inline void | krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags) | { | raw_spin_unlock(&krcp->lock); | local_irq_restore(flags); | }
instead of raw_spin_unlock_irqrestore()? Should something with the locked section trigger a scheduling event by setting TIF_NEED_RESCHED then there will be no scheduling event on unlock. It will be delayed until a later "random" preempt_enable().
raw_spin_unlock_irqrestore() will reschedule if the flag is set, local_irq_restore() will not.
Sebastian
| |