v4.19.13 snapshot.
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
new file mode 100644
index 0000000..c01813c
--- /dev/null
+++ b/include/linux/preempt.h
@@ -0,0 +1,328 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_PREEMPT_H
+#define __LINUX_PREEMPT_H
+
+/*
+ * include/linux/preempt.h - macros for accessing and manipulating
+ * preempt_count (used for kernel preemption, interrupt count, etc.)
+ */
+
+#include <linux/linkage.h>
+#include <linux/list.h>
+
+/*
+ * We put the hardirq and softirq counter into the preemption
+ * counter. The bitmask has the following meaning:
+ *
+ * - bits 0-7 are the preemption count (max preemption depth: 256)
+ * - bits 8-15 are the softirq count (max # of softirqs: 256)
+ *
+ * The hardirq count could in theory be the same as the number of
+ * interrupts in the system, but we run all interrupt handlers with
+ * interrupts disabled, so we cannot have nesting interrupts. Though
+ * there are a few palaeontologic drivers which reenable interrupts in
+ * the handler, so we need more than one bit here.
+ *
+ * PREEMPT_MASK: 0x000000ff
+ * SOFTIRQ_MASK: 0x0000ff00
+ * HARDIRQ_MASK: 0x000f0000
+ * NMI_MASK: 0x00100000
+ * PREEMPT_NEED_RESCHED: 0x80000000
+ */
+#define PREEMPT_BITS 8
+#define SOFTIRQ_BITS 8
+#define HARDIRQ_BITS 4
+#define NMI_BITS 1
+
+#define PREEMPT_SHIFT 0
+#define SOFTIRQ_SHIFT (PREEMPT_SHIFT + PREEMPT_BITS)
+#define HARDIRQ_SHIFT (SOFTIRQ_SHIFT + SOFTIRQ_BITS)
+#define NMI_SHIFT (HARDIRQ_SHIFT + HARDIRQ_BITS)
+
+#define __IRQ_MASK(x) ((1UL << (x))-1)
+
+#define PREEMPT_MASK (__IRQ_MASK(PREEMPT_BITS) << PREEMPT_SHIFT)
+#define SOFTIRQ_MASK (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT)
+#define HARDIRQ_MASK (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT)
+#define NMI_MASK (__IRQ_MASK(NMI_BITS) << NMI_SHIFT)
+
+#define PREEMPT_OFFSET (1UL << PREEMPT_SHIFT)
+#define SOFTIRQ_OFFSET (1UL << SOFTIRQ_SHIFT)
+#define HARDIRQ_OFFSET (1UL << HARDIRQ_SHIFT)
+#define NMI_OFFSET (1UL << NMI_SHIFT)
+
+#define SOFTIRQ_DISABLE_OFFSET (2 * SOFTIRQ_OFFSET)
+
+/* We use the MSB mostly because its available */
+#define PREEMPT_NEED_RESCHED 0x80000000
+
+#define PREEMPT_DISABLED (PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED)
+
+/*
+ * Disable preemption until the scheduler is running -- use an unconditional
+ * value so that it also works on !PREEMPT_COUNT kernels.
+ *
+ * Reset by start_kernel()->sched_init()->init_idle()->init_idle_preempt_count().
+ */
+#define INIT_PREEMPT_COUNT PREEMPT_OFFSET
+
+/*
+ * Initial preempt_count value; reflects the preempt_count schedule invariant
+ * which states that during context switches:
+ *
+ * preempt_count() == 2*PREEMPT_DISABLE_OFFSET
+ *
+ * Note: PREEMPT_DISABLE_OFFSET is 0 for !PREEMPT_COUNT kernels.
+ * Note: See finish_task_switch().
+ */
+#define FORK_PREEMPT_COUNT (2*PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED)
+
+/* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */
+#include <asm/preempt.h>
+
+#define hardirq_count() (preempt_count() & HARDIRQ_MASK)
+#define softirq_count() (preempt_count() & SOFTIRQ_MASK)
+#define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \
+ | NMI_MASK))
+
+/*
+ * Are we doing bottom half or hardware interrupt processing?
+ *
+ * in_irq() - We're in (hard) IRQ context
+ * in_softirq() - We have BH disabled, or are processing softirqs
+ * in_interrupt() - We're in NMI,IRQ,SoftIRQ context or have BH disabled
+ * in_serving_softirq() - We're in softirq context
+ * in_nmi() - We're in NMI context
+ * in_task() - We're in task context
+ *
+ * Note: due to the BH disabled confusion: in_softirq(),in_interrupt() really
+ * should not be used in new code.
+ */
+#define in_irq() (hardirq_count())
+#define in_softirq() (softirq_count())
+#define in_interrupt() (irq_count())
+#define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET)
+#define in_nmi() (preempt_count() & NMI_MASK)
+#define in_task() (!(preempt_count() & \
+ (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
+
+/*
+ * The preempt_count offset after preempt_disable();
+ */
+#if defined(CONFIG_PREEMPT_COUNT)
+# define PREEMPT_DISABLE_OFFSET PREEMPT_OFFSET
+#else
+# define PREEMPT_DISABLE_OFFSET 0
+#endif
+
+/*
+ * The preempt_count offset after spin_lock()
+ */
+#define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET
+
+/*
+ * The preempt_count offset needed for things like:
+ *
+ * spin_lock_bh()
+ *
+ * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and
+ * softirqs, such that unlock sequences of:
+ *
+ * spin_unlock();
+ * local_bh_enable();
+ *
+ * Work as expected.
+ */
+#define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_LOCK_OFFSET)
+
+/*
+ * Are we running in atomic context? WARNING: this macro cannot
+ * always detect atomic context; in particular, it cannot know about
+ * held spinlocks in non-preemptible kernels. Thus it should not be
+ * used in the general case to determine whether sleeping is possible.
+ * Do not use in_atomic() in driver code.
+ */
+#define in_atomic() (preempt_count() != 0)
+
+/*
+ * Check whether we were atomic before we did preempt_disable():
+ * (used by the scheduler)
+ */
+#define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET)
+
+#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_TRACE_PREEMPT_TOGGLE)
+extern void preempt_count_add(int val);
+extern void preempt_count_sub(int val);
+#define preempt_count_dec_and_test() \
+ ({ preempt_count_sub(1); should_resched(0); })
+#else
+#define preempt_count_add(val) __preempt_count_add(val)
+#define preempt_count_sub(val) __preempt_count_sub(val)
+#define preempt_count_dec_and_test() __preempt_count_dec_and_test()
+#endif
+
+#define __preempt_count_inc() __preempt_count_add(1)
+#define __preempt_count_dec() __preempt_count_sub(1)
+
+#define preempt_count_inc() preempt_count_add(1)
+#define preempt_count_dec() preempt_count_sub(1)
+
+#ifdef CONFIG_PREEMPT_COUNT
+
+#define preempt_disable() \
+do { \
+ preempt_count_inc(); \
+ barrier(); \
+} while (0)
+
+#define sched_preempt_enable_no_resched() \
+do { \
+ barrier(); \
+ preempt_count_dec(); \
+} while (0)
+
+#define preempt_enable_no_resched() sched_preempt_enable_no_resched()
+
+#define preemptible() (preempt_count() == 0 && !irqs_disabled())
+
+#ifdef CONFIG_PREEMPT
+#define preempt_enable() \
+do { \
+ barrier(); \
+ if (unlikely(preempt_count_dec_and_test())) \
+ __preempt_schedule(); \
+} while (0)
+
+#define preempt_enable_notrace() \
+do { \
+ barrier(); \
+ if (unlikely(__preempt_count_dec_and_test())) \
+ __preempt_schedule_notrace(); \
+} while (0)
+
+#define preempt_check_resched() \
+do { \
+ if (should_resched(0)) \
+ __preempt_schedule(); \
+} while (0)
+
+#else /* !CONFIG_PREEMPT */
+#define preempt_enable() \
+do { \
+ barrier(); \
+ preempt_count_dec(); \
+} while (0)
+
+#define preempt_enable_notrace() \
+do { \
+ barrier(); \
+ __preempt_count_dec(); \
+} while (0)
+
+#define preempt_check_resched() do { } while (0)
+#endif /* CONFIG_PREEMPT */
+
+#define preempt_disable_notrace() \
+do { \
+ __preempt_count_inc(); \
+ barrier(); \
+} while (0)
+
+#define preempt_enable_no_resched_notrace() \
+do { \
+ barrier(); \
+ __preempt_count_dec(); \
+} while (0)
+
+#else /* !CONFIG_PREEMPT_COUNT */
+
+/*
+ * Even if we don't have any preemption, we need preempt disable/enable
+ * to be barriers, so that we don't have things like get_user/put_user
+ * that can cause faults and scheduling migrate into our preempt-protected
+ * region.
+ */
+#define preempt_disable() barrier()
+#define sched_preempt_enable_no_resched() barrier()
+#define preempt_enable_no_resched() barrier()
+#define preempt_enable() barrier()
+#define preempt_check_resched() do { } while (0)
+
+#define preempt_disable_notrace() barrier()
+#define preempt_enable_no_resched_notrace() barrier()
+#define preempt_enable_notrace() barrier()
+#define preemptible() 0
+
+#endif /* CONFIG_PREEMPT_COUNT */
+
+#ifdef MODULE
+/*
+ * Modules have no business playing preemption tricks.
+ */
+#undef sched_preempt_enable_no_resched
+#undef preempt_enable_no_resched
+#undef preempt_enable_no_resched_notrace
+#undef preempt_check_resched
+#endif
+
+#define preempt_set_need_resched() \
+do { \
+ set_preempt_need_resched(); \
+} while (0)
+#define preempt_fold_need_resched() \
+do { \
+ if (tif_need_resched()) \
+ set_preempt_need_resched(); \
+} while (0)
+
+#ifdef CONFIG_PREEMPT_NOTIFIERS
+
+struct preempt_notifier;
+
+/**
+ * preempt_ops - notifiers called when a task is preempted and rescheduled
+ * @sched_in: we're about to be rescheduled:
+ * notifier: struct preempt_notifier for the task being scheduled
+ * cpu: cpu we're scheduled on
+ * @sched_out: we've just been preempted
+ * notifier: struct preempt_notifier for the task being preempted
+ * next: the task that's kicking us out
+ *
+ * Please note that sched_in and out are called under different
+ * contexts. sched_out is called with rq lock held and irq disabled
+ * while sched_in is called without rq lock and irq enabled. This
+ * difference is intentional and depended upon by its users.
+ */
+struct preempt_ops {
+ void (*sched_in)(struct preempt_notifier *notifier, int cpu);
+ void (*sched_out)(struct preempt_notifier *notifier,
+ struct task_struct *next);
+};
+
+/**
+ * preempt_notifier - key for installing preemption notifiers
+ * @link: internal use
+ * @ops: defines the notifier functions to be called
+ *
+ * Usually used in conjunction with container_of().
+ */
+struct preempt_notifier {
+ struct hlist_node link;
+ struct preempt_ops *ops;
+};
+
+void preempt_notifier_inc(void);
+void preempt_notifier_dec(void);
+void preempt_notifier_register(struct preempt_notifier *notifier);
+void preempt_notifier_unregister(struct preempt_notifier *notifier);
+
+static inline void preempt_notifier_init(struct preempt_notifier *notifier,
+ struct preempt_ops *ops)
+{
+ INIT_HLIST_NODE(¬ifier->link);
+ notifier->ops = ops;
+}
+
+#endif
+
+#endif /* __LINUX_PREEMPT_H */