From: Steven Rostedt <[email protected]> In order to switch the protection of tracepoint callbacks from preempt_disable() to srcu_read_lock_fast() the BPF callback from tracepoints needs to have migration prevention as the BPF programs expect to stay on the same CPU as they execute. Put together the RCU protection with migration prevention and use rcu_read_lock_dont_migrate() in __bpf_trace_run(). This will allow tracepoints callbacks to be preemptible.
Link: https://lore.kernel.org/all/caadnvqkvy026hsfgosavjppm3-ajm-vslzy-oefue+bakmr...@mail.gmail.com/ Suggested-by: Alexei Starovoitov <[email protected]> Signed-off-by: Steven Rostedt (Google) <[email protected]> --- kernel/trace/bpf_trace.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index fe28d86f7c35..abbf0177ad20 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2062,7 +2062,7 @@ void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args) struct bpf_run_ctx *old_run_ctx; struct bpf_trace_run_ctx run_ctx; - cant_sleep(); + rcu_read_lock_dont_migrate(); if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) { bpf_prog_inc_misses_counter(prog); goto out; @@ -2071,13 +2071,12 @@ void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args) run_ctx.bpf_cookie = link->cookie; old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx); - rcu_read_lock(); (void) bpf_prog_run(prog, args); - rcu_read_unlock(); bpf_reset_run_ctx(old_run_ctx); out: this_cpu_dec(*(prog->active)); + rcu_read_unlock_migrate(); } #define UNPACK(...) __VA_ARGS__ -- 2.51.0
