On 12/8/22 18:00, Jens Axboe wrote:
On 12/8/22 3:01?PM, Waiman Long wrote:
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index 793ecff29038..910e633869b0 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -281,6 +281,26 @@ void cgroup_rstat_flush_release(void)
spin_unlock_irq(&cgroup_rstat_lock);
}
+/**
+ * cgroup_rstat_css_cpu_flush - flush stats for the given css and cpu
+ * @css: target css to be flush
+ * @cpu: the cpu that holds the stats to be flush
+ *
+ * A lightweight rstat flush operation for a given css and cpu.
+ * Only the cpu_lock is being held for mutual exclusion, the cgroup_rstat_lock
+ * isn't used.
+ */
+void cgroup_rstat_css_cpu_flush(struct cgroup_subsys_state *css, int cpu)
+{
+ raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu);
+
+ raw_spin_lock_irq(cpu_lock);
+ rcu_read_lock();
+ css->ss->css_rstat_flush(css, cpu);
+ rcu_read_unlock();
+ raw_spin_unlock_irq(cpu_lock);
+}
+
int cgroup_rstat_init(struct cgroup *cgrp)
{
int cpu;
As I mentioned last time, raw_spin_lock_irq() will be equivalent to an
RCU protected section anyway, so you don't need to do both. Just add a
comment on why rcu_read_lock()/rcu_read_unlock() isn't needed inside the
raw irq safe lock.
Yes, you are right. We don't need rcu_read_lock() here. I put it there
to follow the locking pattern in cgroup_rstat_flush_locked(). I will
remove it in the next version.
Cheers,
Longman
