This has the wrong explanation of the proposed rseq (Restartable Sequences) solution.

> a Linux kernel facility that lets userspace code detect whether it was preempted or migrated during a critical section and restart it if so. PostgreSQL's spinlock paths would use rseq to detect preemption and retry, avoiding the scenario where a preempted lock holder stalls all waiting backends.

The real proposal is about time-slice extension, which is a feature that uses the abi for rseq but otherwise has nothing to do with retrying critical sections. While a process holds a s_lock, it would set a request bit. If the kernel tries to preempt that thread while the request bit is set, it instead extends the time slice once and returns control back to the thread. It's further explained here: https://docs.kernel.org/userspace-api/rseq.html