From f7d327654b886a768fb3baa5b43d151b63e2d4ff Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Mon, 26 Jan 2026 18:11:47 -0500 Subject: [PATCH] bpf: Have __bpf_trace_run() use rcu_read_lock_dont_migrate() 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+BaKMRnDg@mail.gmail.com/ Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: "Paul E. McKenney" Cc: Sebastian Andrzej Siewior Cc: Alexei Starovoitov Link: https://patch.msgid.link/20260126231256.335034877@kernel.org Suggested-by: Alexei Starovoitov Signed-off-by: Steven Rostedt (Google) --- 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 fe28d86f7c357..abbf0177ad20b 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__ -- 2.47.3