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    SubjectRe: [patch 30/63] locking/spinlock: Provide RT variant
    Date
    On 7/30/21 9:50 AM, Thomas Gleixner wrote:
    > From: Thomas Gleixner <tglx@linutronix.de>
    >
    > Provide the actual locking functions which make use of the general and
    > spinlock specific rtmutex code.
    >
    > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    > ---
    > 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

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