Stable backports

Hi,

I've been looking over my queue and which patches vanishes (as in
applied somewhere) and did not show up in the stable tree. Here is a
list of some suggestions:

- 7eb16f23b9a41 ("io-mapping: don't disable preempt on RT in io_mapping_map_atomic_wc().")
- 286deb7ec03d9 ("locking/rwbase: Mitigate indefinite writer starvation")
- 1c0908d8e4416 ("rtmutex: Add acquire semantics for rtmutex lock acquisition slow path")
  (is in v6.1 but not in v5.15)
- b8a04a538ed47 ("revert: "softirq: Let ksoftirqd do its job"")
- 38cdd83a47fb2 ("tracing/timer: Add missing hrtimer modes to decode_hrtimer_mode().")

Sebastian