6.6-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 8903db0b59602..a896b80252ae1 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2726,18 +2726,23 @@ 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);