From: Hou Tao <houtao1@xxxxxxxxxx>
The memory free logic in bpf memory allocator chains a RCU Tasks Trace
grace period and a normal RCU grace period one after the other, so it
can ensure that both sleepable and non-sleepable programs have finished.
With the introduction of rcu_trace_implies_rcu_gp(),
__free_rcu_tasks_trace() can check whether or not a normal RCU grace
period has also passed after a RCU Tasks Trace grace period has passed.
If it is true, freeing these elements directly, else freeing through
call_rcu().
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
kernel/bpf/memalloc.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c
index 5f83be1d2018..2433be58bb85 100644
--- a/kernel/bpf/memalloc.c
+++ b/kernel/bpf/memalloc.c
@@ -222,9 +222,13 @@ static void __free_rcu(struct rcu_head *head)
static void __free_rcu_tasks_trace(struct rcu_head *head)
{
- struct bpf_mem_cache *c = container_of(head, struct bpf_mem_cache, rcu);
-
- call_rcu(&c->rcu, __free_rcu);
+ /* If RCU Tasks Trace grace period implies RCU grace period,
+ * there is no need to invoke call_rcu().
+ */
+ if (rcu_trace_implies_rcu_gp())
+ __free_rcu(head);
+ else
+ call_rcu(head, __free_rcu);
}
static void enque_to_free(struct bpf_mem_cache *c, void *obj)
@@ -253,8 +257,9 @@ static void do_call_rcu(struct bpf_mem_cache *c)
*/
__llist_add(llnode, &c->waiting_for_gp);
/* Use call_rcu_tasks_trace() to wait for sleepable progs to finish.
- * Then use call_rcu() to wait for normal progs to finish
- * and finally do free_one() on each element.
+ * If RCU Tasks Trace grace period implies RCU grace period, free
+ * these elements directly, else use call_rcu() to wait for normal
+ * progs to finish and finally do free_one() on each element.
*/
call_rcu_tasks_trace(&c->rcu, __free_rcu_tasks_trace);
}
--
2.29.2
