From: Hou Tao <houtao1@xxxxxxxxxx>
According to the implementation of RCU Tasks Trace, it inovkes
->postscan_func() to wait for one RCU-tasks-trace grace period and
rcu_tasks_trace_postscan() inovkes synchronize_rcu() to wait for one
normal RCU grace period in turn, so one RCU-tasks-trace grace period
will imply one RCU grace period.
So there is no need to do call_rcu() again in the callback of
call_rcu_tasks_trace() and it can just free these elements directly.
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
kernel/bpf/memalloc.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c
index 5f83be1d2018..6f32dddc804f 100644
--- a/kernel/bpf/memalloc.c
+++ b/kernel/bpf/memalloc.c
@@ -209,6 +209,9 @@ static void free_one(struct bpf_mem_cache *c, void *obj)
kfree(obj);
}
+/* Now RCU Tasks grace period implies RCU grace period, so no need to do
+ * an extra call_rcu().
+ */
static void __free_rcu(struct rcu_head *head)
{
struct bpf_mem_cache *c = container_of(head, struct bpf_mem_cache, rcu);
@@ -220,13 +223,6 @@ static void __free_rcu(struct rcu_head *head)
atomic_set(&c->call_rcu_in_progress, 0);
}
-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);
-}
-
static void enque_to_free(struct bpf_mem_cache *c, void *obj)
{
struct llist_node *llnode = obj;
@@ -252,11 +248,10 @@ static void do_call_rcu(struct bpf_mem_cache *c)
* from __free_rcu() and from drain_mem_cache().
*/
__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.
+ /* Use call_rcu_tasks_trace() to wait for both sleepable and normal
+ * progs to finish and finally do free_one() on each element.
*/
- call_rcu_tasks_trace(&c->rcu, __free_rcu_tasks_trace);
+ call_rcu_tasks_trace(&c->rcu, __free_rcu);
}
static void free_bulk(struct bpf_mem_cache *c)
--
2.29.2
