A CONFIG_PREEMPT_COUNT is unconditionally enabled, thus a page can be obtained directly from a kvfree_rcu() path. To distinguish that and take a decision the preemptable() macro is used when it is save to enter allocator.
It means that refilling a cache is not important from timing point of view. Switch to a delayed work, so the actual work is queued from the timer interrupt with 1 jiffy delay. An immediate placing a task on a current CPU can lead to rq->lock double lock. That is why a delayed method is in place. Signed-off-by: Uladzislau Rezki (Sony) <[email protected]> --- kernel/rcu/tree.c | 26 +++++--------------------- 1 file changed, 5 insertions(+), 21 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 3f9b016a44dc..9ea55f800b4b 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3086,7 +3086,6 @@ struct kfree_rcu_cpu_work { * per-cpu lock. * @page_cache_work: A work to refill the cache when it is empty * @work_in_progress: Indicates that page_cache_work is running - * @hrtimer: A hrtimer for scheduling a page_cache_work * @nr_bkv_objs: number of allocated objects at @bkvcache. * * This is a per-CPU structure. The reason that it is not included in @@ -3104,9 +3103,8 @@ struct kfree_rcu_cpu { bool initialized; int count; - struct work_struct page_cache_work; + struct delayed_work page_cache_work; atomic_t work_in_progress; - struct hrtimer hrtimer; struct llist_head bkvcache; int nr_bkv_objs; @@ -3355,22 +3353,12 @@ static void kfree_rcu_monitor(struct work_struct *work) raw_spin_unlock_irqrestore(&krcp->lock, flags); } -static enum hrtimer_restart -schedule_page_work_fn(struct hrtimer *t) -{ - struct kfree_rcu_cpu *krcp = - container_of(t, struct kfree_rcu_cpu, hrtimer); - - queue_work(system_highpri_wq, &krcp->page_cache_work); - return HRTIMER_NORESTART; -} - static void fill_page_cache_func(struct work_struct *work) { struct kvfree_rcu_bulk_data *bnode; struct kfree_rcu_cpu *krcp = container_of(work, struct kfree_rcu_cpu, - page_cache_work); + page_cache_work.work); unsigned long flags; bool pushed; int i; @@ -3398,12 +3386,8 @@ static void run_page_cache_worker(struct kfree_rcu_cpu *krcp) { if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && - !atomic_xchg(&krcp->work_in_progress, 1)) { - hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, - HRTIMER_MODE_REL); - krcp->hrtimer.function = schedule_page_work_fn; - hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL); - } + !atomic_xchg(&krcp->work_in_progress, 1)) + schedule_delayed_work(&krcp->page_cache_work, 1); } // Record ptr in a page managed by krcp, with the pre-krc_this_cpu_lock() @@ -4503,7 +4487,7 @@ static void __init kfree_rcu_batch_init(void) } INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor); - INIT_WORK(&krcp->page_cache_work, fill_page_cache_func); + INIT_DELAYED_WORK(&krcp->page_cache_work, fill_page_cache_func); krcp->initialized = true; } if (register_shrinker(&kfree_rcu_shrinker)) -- 2.20.1
