On Mon, Jun 08, 2020 at 01:58:00PM +0200, Peter Zijlstra wrote:
> Hi Jens,
>
> I've been going through smp_call_function_single_async() users and
> stumbled upon blk-softirq.c, which has:
>
> static int raise_blk_irq(int cpu, struct request *rq)
> {
> if (cpu_online(cpu)) {
> call_single_data_t *data = &rq->csd;
>
> data->func = trigger_softirq;
> data->info = rq;
> data->flags = 0;
>
> smp_call_function_single_async(cpu, data);
> return 0;
> }
>
> return 1;
> }
>
> What, if anything, guarantees rq->csd is not already in use at that
> time?
A request can only be completed once.
