Messages in this thread | | | Date | Fri, 21 Oct 2022 10:36:35 +0200 | From | Andrea Parri <> | Subject | Re: [PATCH] riscv: fix race when vmap stack overflow |
| |
> > > + atomic_set_release(&spin_shadow_stack, 0); > > > > Have not really looked the details: should there be a matching acquire? > > 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. > > The following memory operations order is not important, because we > just care about sp value. > > Also, we use relax amoswap before, because sp has naturelly > dependency. But giving them RCsc is okay here, because we don't care > about performance here.
Thanks for the clarification.
I'm not really suggesting to add unneeded synchronization, even more so in local/private constructs as in this case. It just felt odd to see the release without a pairing acquire, so I asked. ;-)
Thanks, Andrea
> eg: > handle_kernel_stack_overflow: > +1: la sp, spin_shadow_stack > + amoswap.w.aqrl sp, sp, (sp) > + bnez sp, 1b > + > .... > + smp_store_release(&spin_shadow_stack, 0); > + smp_mb();
| |