[PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32

[Peter Zijlstra]

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.