bpf: remove unnecessary rcu_read_lock in kprobe_multi_link_prog_run

Preemption is disabled in ftrace graph, which indicate rcu_read_lock. So
the rcu_read_lock is not needed in fprobe_entry(), and it is not needed
in kprobe_multi_link_prog_run() neither.

Signed-off-by: Menglong Dong <[email protected]>

Author: image-dragon

kernel/trace/bpf_trace.c

@@ -2741,12 +2741,10 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
 		goto out;
 	}
 
-	rcu_read_lock();
 	regs = ftrace_partial_regs(fregs, bpf_kprobe_multi_pt_regs_ptr());
 	old_run_ctx = bpf_set_run_ctx(&run_ctx.session_ctx.run_ctx);
 	err = bpf_prog_run(link->link.prog, regs);
 	bpf_reset_run_ctx(old_run_ctx);
-	rcu_read_unlock();
 
  out:
 	__this_cpu_dec(bpf_prog_active);