Re: [PATCH] riscv: fix race when vmap stack overflow

[Tong Tiangen]

在 2022/10/21 21:22, Andrea Parri 写道:
> Hi Tong,
>   
> > > > I use atomic_set_release here, because I need earlier memory
> > > > operations finished to make sure the sp is ready then set the spin
> > > > flag.
>
> > 	Consider this implementation:)
> >
> > 	smp_store_mb(&spin_shadow_stack, 0);
>
> smp_store_mb() has "WRITE_ONCE(); smp_mb()" semantics; so it doesn't
> guarantee that the store to spin_shadow_stack is ordered after program
> -order earlier memory accesses.
>
>    Andrea
> .

Hi Andrea:

IIUC, the earlier memory access amoswap.aqrl, here .aqrl guarantee it.
But anyway, consider we don't care about performance here, using 
smp_store_release()(add barrier()) surely right.

Thanks,
Tong.