bpf: Remove migrate_disable in kprobe_multi_link_prog_run

[ Upstream commit abdaf49be5424db74e19d167c10d7dad79a0efc2 ]

Graph tracer framework ensures we won't migrate, kprobe_multi_link_prog_run
called all the way from graph tracer, which disables preemption in
function_graph_enter_regs, as Jiri and Yonghong suggested, there is no
need to use migrate_disable. As a result, some overhead may will be reduced.
And add cant_sleep check for __this_cpu_inc_return.

Fixes: 0dcac2725406 ("bpf: Add multi kprobe link")
Signed-off-by: Tao Chen <chen.dylane@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250814121430.2347454-1-chen.dylane@linux.dev
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 243122ca567930b9554792f8db1a58215976a6d1..e6fde598f7629035797bec1bbd1a25a7e04385ec 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2636,18 +2636,23 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
        struct bpf_run_ctx *old_run_ctx;
        int err;
 
+       /*
+        * graph tracer framework ensures we won't migrate, so there is no need
+        * to use migrate_disable for bpf_prog_run again. The check here just for
+        * __this_cpu_inc_return.
+        */
+       cant_sleep();
+
        if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
                err = 0;
                goto out;
        }
 
-       migrate_disable();
        rcu_read_lock();
        old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
        err = bpf_prog_run(link->link.prog, regs);
        bpf_reset_run_ctx(old_run_ctx);
        rcu_read_unlock();
-       migrate_enable();
 
  out:
        __this_cpu_dec(bpf_prog_active);