[PATCH 1/2] rcu/kvfree: Remove useless monitor_todo flag

From: Uladzislau Rezki (Sony)
Date: Thu Jun 02 2022 - 04:07:10 EST


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;
+}
+
/*
* 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