This series add PREEMPT_RT support for LoongArch.

With the recent printk changes, the last known road block has been
addressed. The main architectural preparation we need is selecting
HAVE_POSIX_CPU_TIMERS_TASK_WORK to allow PREEMPT_RT coexist with KVM.
Then we can also enable PREEMPT_RT as X86, ARM64 and RISC-V.

V1 -> V2:
1. Fix sleeping in atomic context for PREEMPT_RT.
2. Reduce min_delta to 100 for PREEMPT_RT and update commit messages.

Huacai Chen(4):
 LoongArch: Reduce min_delta for the arch clockevent device.
 LoongArch: Fix sleeping in atomic context for PREEMPT_RT.
 LoongArch: Select HAVE_POSIX_CPU_TIMERS_TASK_WORK.
 LoongArch: Allow to enable PREEMPT_RT.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 arch/loongarch/Kconfig       | 2 ++
 arch/loongarch/kernel/time.c | 6 +++++-
 arch/loongarch/mm/tlb.c      | 2 +-
 3 files changed, 8 insertions(+), 2 deletions(-)
---
2.27.0