Re: [patch 30/63] locking/spinlock: Provide RT variant

[Waiman Long]

On 7/30/21 9:50 AM, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>
> Provide the actual locking functions which make use of the general and
> spinlock specific rtmutex code.
>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> ---
>   kernel/locking/Makefile      |    1
>   kernel/locking/spinlock_rt.c |  128 +++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 129 insertions(+)
>   create mode 100644 kernel/locking/spinlock_rt.c
> ---
> --- a/kernel/locking/Makefile
> +++ b/kernel/locking/Makefile
> @@ -25,6 +25,7 @@ obj-$(CONFIG_LOCK_SPIN_ON_OWNER) += osq_
>   obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
>   obj-$(CONFIG_QUEUED_SPINLOCKS) += qspinlock.o
>   obj-$(CONFIG_RT_MUTEXES) += rtmutex_api.o
> +obj-$(CONFIG_PREEMPT_RT) += spinlock_rt.o
>   obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
>   obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o
>   obj-$(CONFIG_QUEUED_RWLOCKS) += qrwlock.o
> --- /dev/null
> +++ b/kernel/locking/spinlock_rt.c
> @@ -0,0 +1,128 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * PREEMPT_RT substitution for spin/rw_locks
> + *
> + * spin_lock and rw_lock on RT are based on rtmutex with a few twists to
> + * resemble the non RT semantics
> + *
> + * - Contrary to a plain rtmutex, spin_lock and rw_lock are state
> + *   preserving. The task state is saved before blocking on the underlying
> + *   rtmutex and restored when the lock has been acquired. Regular wakeups
> + *   during that time are redirected to the saved state so no wake up is
> + *   missed.
> + *
> + * - Non RT spin/rw_locks disable preemption and evtl. interrupts.

"evtl."?

Cheers,
Longman