[$] A new type of spinlock for the BPF subsystem

The 6.15 merge window saw the inclusion of a new type of lock for BPF programs:
a resilient queued spinlock that Kumar Kartikeya Dwivedi has been working on
for some time. Eventually, he hopes to convert all of the spinlocks currently
used in the BPF subsystem to his new lock.
He gave a remote presentation about the design of the lock at the
2025 Linux Storage, Filesystem,
Memory-Management, and BPF summit.