On Wed, Apr 07, 2021 at 05:51:07PM +0200, Peter Zijlstra wrote: > On Wed, Apr 07, 2021 at 04:29:12PM +0200, Christoph Müllner wrote: > > Further, it is not the case that RISC-V has no guarantees at all. > > It just does not provide a forward progress guarantee for a > > synchronization implementation, > > that writes in an endless loop to a memory location while trying to > > complete an LL/SC > > loop on the same memory location at the same time. > > Userspace can DoS the kernel that way, see futex. The longer answer is that this means you cannot share locks (or any atomic really) across a trust boundary, which is of course exactly what futex does.
