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@xxxxxxxxx>
---
kernel/trace/bpf_trace.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
Change list:
v1 -> v2:
- s/called the way/called all the way/.(Jiri)
v1: https://lore.kernel.org/bpf/f7acfd22-bcf3-4dff-9a87-7c1e6f84ce9c@xxxxxxxxx
v2 -> v3:
- add cant_sleep for __this_cpu_inc_return.(Andrii)
- shorten comments.(Andrii)
v2: https://lore.kernel.org/bpf/20250805162732.1896687-1-chen.dylane@xxxxxxxxx
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 3ae52978cae..606007c387c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2728,20 +2728,25 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
struct pt_regs *regs;
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)) {
bpf_prog_inc_misses_counter(link->link.prog);
err = 1;
goto out;
}
- migrate_disable();
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();
- migrate_enable();
out:
__this_cpu_dec(bpf_prog_active);
--
2.48.1
