6.17-stable review patch. If anyone has any objections, please let me know.
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From: Tao Chen chen.dylane@linux.dev
[ 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 --- kernel/trace/bpf_trace.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 3ae52978cae61..606007c387c52 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);