Re: [PATCH bpf-next v8 2/3] perf: Refactor get_perf_callchain

[Peter Zijlstra]

On Mon, Jan 26, 2026 at 03:43:30PM +0800, Tao Chen wrote:
> From BPF stack map, we want to ensure that the callchain buffer
> will not be overwritten by other preemptive tasks and we also aim
> to reduce the preempt disable interval, Based on the suggestions from Peter
> and Andrrii, export new API __get_perf_callchain and the usage scenarios
> are as follows from BPF side:
> 
> preempt_disable()
> entry = get_callchain_entry()
> preempt_enable()
> __get_perf_callchain(entry)
> put_callchain_entry(entry)

That makes no sense, this means any other task on that CPU is getting
screwed over.

Why are you worried about the preempt_disable() here? If this were an
interrupt context we'd still do that unwind -- but then with IRQs
disabled.