Re: [PATCH] RDMA/siw: Reuse value read using READ_ONCE instead of re-reading it

[Greg Sword]

On Sun, Mar 10, 2024 at 8:36 PM linke li <lilinke99@xxxxxx> wrote:
>
> > In a complicated environment, for example, this function is called many
> > times at the same time and orqe->flags is changed at the same time, I am
> > not sure if this will introduce risks or not.
>
> I think one function of READ_ONCE is to read a valid value while the value
> may change concurrently. And there is a smp() above the READ_ONCE, which
> means that the READ_ONCE is well ordered. I think it is kind of safe here.

This is not a smp problem. Compared with the original source, your
commit introduces a time slot.

>
> > if you need to ensure the consistency of the flags throughout the function, not sure if the following is better or not.
>
> > if (((orqe_flags=READ_ONCE(orqe->flags))) & SIW_WQE_VALID) {
>
> This patch looks like exactly do the same things. The only difference I
> think is the code style.

No.

>
> Thanks,
> Linke
>
>