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authorHou Tao <houtao1@huawei.com>2022-12-09 09:09:47 +0800
committerAlexei Starovoitov <ast@kernel.org>2022-12-08 17:50:17 -0800
commit822ed78fab13d5a54f8b8c030e8c5dc0fcd2cdae (patch)
tree8715fbbde0c80e21ce62e7b1e4e71ca279f37e35 /kernel/bpf/memalloc.c
parent0893d6007db5cf397f3fc92b2a6935c3ed0c6f00 (diff)
bpf: Skip rcu_barrier() if rcu_trace_implies_rcu_gp() is true
If there are pending rcu callback, free_mem_alloc() will use rcu_barrier_tasks_trace() and rcu_barrier() to wait for the pending __free_rcu_tasks_trace() and __free_rcu() callback. If rcu_trace_implies_rcu_gp() is true, there will be no pending __free_rcu(), so it will be OK to skip rcu_barrier() as well. Acked-by: Yonghong Song <yhs@fb.com> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/r/20221209010947.3130477-3-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf/memalloc.c')
-rw-r--r--kernel/bpf/memalloc.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c
index 04d96d1b98a3..ebcc3dd0fa19 100644
--- a/kernel/bpf/memalloc.c
+++ b/kernel/bpf/memalloc.c
@@ -464,9 +464,17 @@ static void free_mem_alloc(struct bpf_mem_alloc *ma)
{
/* waiting_for_gp lists was drained, but __free_rcu might
* still execute. Wait for it now before we freeing percpu caches.
+ *
+ * rcu_barrier_tasks_trace() doesn't imply synchronize_rcu_tasks_trace(),
+ * but rcu_barrier_tasks_trace() and rcu_barrier() below are only used
+ * to wait for the pending __free_rcu_tasks_trace() and __free_rcu(),
+ * so if call_rcu(head, __free_rcu) is skipped due to
+ * rcu_trace_implies_rcu_gp(), it will be OK to skip rcu_barrier() by
+ * using rcu_trace_implies_rcu_gp() as well.
*/
rcu_barrier_tasks_trace();
- rcu_barrier();
+ if (!rcu_trace_implies_rcu_gp())
+ rcu_barrier();
free_mem_alloc_no_barrier(ma);
}