Re: [PATCHv2 bpf-next 01/24] bpf: Add multi uprobe link

Alexei Starovoitov
2023-06-20T17:11:20Z

On Tue, Jun 20, 2023 at 10:35:27AM +0200, Jiri Olsa wrote:
> +static int uprobe_prog_run(struct bpf_uprobe *uprobe,
> + unsigned long entry_ip,
> + struct pt_regs *regs)
> +{
> + struct bpf_uprobe_multi_link *link = uprobe->link;
> + struct bpf_uprobe_multi_run_ctx run_ctx = {
> + .entry_ip = entry_ip,
> + };
> + struct bpf_prog *prog = link->link.prog;
> + struct bpf_run_ctx *old_run_ctx;
> + int err = 0;
> +
> + might_fault();
> +
> + rcu_read_lock_trace();
> + migrate_disable();
> +
> + if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1))
> + goto out;

bpf_prog_run_array_sleepable() doesn't do such things.
Such 'proteciton' will actively hurt.
The sleepable prog below will block all kprobes on this cpu.
please remove.

> +
> + old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> +
> + if (!prog->aux->sleepable)
> + rcu_read_lock();
> +
> + err = bpf_prog_run(link->link.prog, regs);
> +
> + if (!prog->aux->sleepable)
> + rcu_read_unlock();
> +
> + bpf_reset_run_ctx(old_run_ctx);
> +
> +out:
> + __this_cpu_dec(bpf_prog_active);
> + migrate_enable();
> + rcu_read_unlock_trace();
> + return err;