On Thu, Jun 02, 2022 at 11:43:39PM +0000, Joel Fernandes wrote:
> On Thu, Jun 02, 2022 at 10:06:43AM +0200, Uladzislau Rezki (Sony) wrote:
> > From: "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx>
> >
> > monitor_todo is not needed as the work struct already tracks
> > if work is pending. Just use that to know if work is pending
> > using schedule_delayed_work() helper.
> >
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> > Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
> > ---
> > kernel/rcu/tree.c | 33 ++++++++++++++++-----------------
> > 1 file changed, 16 insertions(+), 17 deletions(-)
> >
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 222d59299a2a..fd16c0b46d9e 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -3295,7 +3295,6 @@ struct kfree_rcu_cpu_work {
> > * @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period
> > * @lock: Synchronize access to this structure
> > * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES
> > - * @monitor_todo: Tracks whether a @monitor_work delayed work is pending
> > * @initialized: The @rcu_work fields have been initialized
> > * @count: Number of objects for which GP not started
> > * @bkvcache:
> > @@ -3320,7 +3319,6 @@ struct kfree_rcu_cpu {
> > struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES];
> > raw_spinlock_t lock;
> > struct delayed_work monitor_work;
> > - bool monitor_todo;
> > bool initialized;
> > int count;
> >
> > @@ -3500,6 +3498,18 @@ static void kfree_rcu_work(struct work_struct *work)
> > }
> > }
> >
> > +static bool
> > +need_offload_krc(struct kfree_rcu_cpu *krcp)
> > +{
> > + int i;
> > +
> > + for (i = 0; i < FREE_N_CHANNELS; i++)
> > + if (krcp->bkvhead[i])
> > + return true;
> > +
> > + return !!krcp->head;
> > +}
>
> Thanks for modifying my original patch to do this, and thanks for giving me
> the attribution for the patch. This function is a nice addition.
>
> For the patch in its entirety:
> Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
I pulled this one in for testing and further review, thank you both!
Given the description, I reversed the order of the Signed-off-by
tags to indicate that the patch came through Uladzislau from Joel.
Thanx, Paul
> thanks,
>
> - Joel
>
>
>
> > +
> > /*
> > * This function is invoked after the KFREE_DRAIN_JIFFIES timeout.
> > */
> > @@ -3556,9 +3566,7 @@ static void kfree_rcu_monitor(struct work_struct *work)
> > // of the channels that is still busy we should rearm the
> > // work to repeat an attempt. Because previous batches are
> > // still in progress.
> > - if (!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head)
> > - krcp->monitor_todo = false;
> > - else
> > + if (need_offload_krc(krcp))
> > schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
> >
> > raw_spin_unlock_irqrestore(&krcp->lock, flags);
> > @@ -3746,11 +3754,8 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
> > WRITE_ONCE(krcp->count, krcp->count + 1);
> >
> > // Set timer to drain after KFREE_DRAIN_JIFFIES.
> > - if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
> > - !krcp->monitor_todo) {
> > - krcp->monitor_todo = true;
> > + if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING)
> > schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
> > - }
> >
> > unlock_return:
> > krc_this_cpu_unlock(krcp, flags);
> > @@ -3825,14 +3830,8 @@ void __init kfree_rcu_scheduler_running(void)
> > struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
> >
> > raw_spin_lock_irqsave(&krcp->lock, flags);
> > - if ((!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) ||
> > - krcp->monitor_todo) {
> > - raw_spin_unlock_irqrestore(&krcp->lock, flags);
> > - continue;
> > - }
> > - krcp->monitor_todo = true;
> > - schedule_delayed_work_on(cpu, &krcp->monitor_work,
> > - KFREE_DRAIN_JIFFIES);
> > + if (need_offload_krc(krcp))
> > + schedule_delayed_work_on(cpu, &krcp->monitor_work, KFREE_DRAIN_JIFFIES);
> > raw_spin_unlock_irqrestore(&krcp->lock, flags);
> > }
> > }
> > --
> > 2.30.2
> >
