Re: [PATCH perf/core 08/22] uprobes/x86: Add mapping for optimized uprobe trampolines

Oleg Nesterov
2025-04-27T18:05:25Z

On 04/21, Jiri Olsa wrote:
>
> +struct uprobe_trampoline {
> + struct hlist_node node;
> + unsigned long vaddr;
> + atomic64_t ref;
> +};

I don't really understand the point of uprobe_trampoline->ref...

set_orig_insn/swbp_unoptimize paths don't call uprobe_trampoline_put().
It is only called in unlikely case when swbp_optimize() fails, so perhaps
we can kill this member and uprobe_trampoline_put() ? At least in the initial
version.

> +static void uprobe_trampoline_put(struct uprobe_trampoline *tramp)
> +{
> + if (tramp && atomic64_dec_and_test(&tramp->ref))
> + destroy_uprobe_trampoline(tramp);
> +}

Why does it check tramp != NULL ?

Oleg.