From: Hou Tao <houtao1@xxxxxxxxxx> commit 59be91e5e70a1aa91dfee8088b071f6d05c8a1a3 upstream. 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> Link: https://lore.kernel.org/r/20221014113946.965131-3-houtao@xxxxxxxxxxxxxxx Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> Signed-off-by: Alexey Nepomnyashih <sdl@xxxxxxxx> --- 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 5c4e54e17f95..9a4fb4ea73ef 100644 --- a/kernel/bpf/memalloc.c +++ b/kernel/bpf/memalloc.c @@ -261,9 +261,13 @@ 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) @@ -292,8 +296,9 @@ static void do_call_rcu_ttrace(struct bpf_mem_cache *c) */ __llist_add(llnode, &c->waiting_for_gp_ttrace); /* 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_ttrace, __free_rcu_tasks_trace); } -- 2.43.0
