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Message-ID: <358bde93-4933-4305-ac42-4d6f10c97c08@paulmck-laptop> Date: Thu, 18 May 2023 07:47:32 -0700 From: "Paul E. McKenney" <paulmck@...nel.org> To: Martin KaFai Lau <martin.lau@...ux.dev> Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, bpf@...r.kernel.org, netdev@...r.kernel.org Subject: [PATCH bpf] Use call_rcu_hurry() with synchronize_rcu_mult() The bpf_struct_ops_map_free() function must wait for both an RCU grace period and an RCU Tasks grace period, and so it passes call_rcu() and call_rcu_tasks() to synchronize_rcu_mult(). This works, but on ChromeOS and Android platforms call_rcu() can have lazy semantics, resulting in multi-second delays between call_rcu() invocation and invocation of the corresponding callback. Therefore, substitute call_rcu_hurry() for call_rcu(). Signed-off-by: Paul E. McKenney <paulmck@...nel.org> Cc: Martin KaFai Lau <martin.lau@...ux.dev> Cc: Alexei Starovoitov <ast@...nel.org> Cc: Daniel Borkmann <daniel@...earbox.net> Cc: Andrii Nakryiko <andrii@...nel.org> Cc: Song Liu <song@...nel.org> Cc: Yonghong Song <yhs@...com> Cc: John Fastabend <john.fastabend@...il.com> Cc: KP Singh <kpsingh@...nel.org> Cc: Stanislav Fomichev <sdf@...gle.com> Cc: Hao Luo <haoluo@...gle.com> Cc: Jiri Olsa <jolsa@...nel.org> Cc: <bpf@...r.kernel.org> Cc: <netdev@...r.kernel.org> diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c index d3f0a4825fa6..bacffd6cae60 100644 --- a/kernel/bpf/bpf_struct_ops.c +++ b/kernel/bpf/bpf_struct_ops.c @@ -634,7 +634,7 @@ static void bpf_struct_ops_map_free(struct bpf_map *map) * in the tramopline image to finish before releasing * the trampoline image. */ - synchronize_rcu_mult(call_rcu, call_rcu_tasks); + synchronize_rcu_mult(call_rcu_hurry, call_rcu_tasks); __bpf_struct_ops_map_free(map); }
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