1 files changed, 83 insertions, 0 deletions
diff --git a/include/linux/hrtimer_rearm.h b/include/linux/hrtimer_rearm.h
new file mode 100644
index 000000000000..a6f2e5d5e1c7
--- /dev/null
+++ b/include/linux/hrtimer_rearm.h
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef _LINUX_HRTIMER_REARM_H
+#define _LINUX_HRTIMER_REARM_H
+
+#ifdef CONFIG_HRTIMER_REARM_DEFERRED
+#include <linux/thread_info.h>
+
+void __hrtimer_rearm_deferred(void);
+
+/*
+ * This is purely CPU local, so check the TIF bit first to avoid the overhead of
+ * the atomic test_and_clear_bit() operation for the common case where the bit
+ * is not set.
+ */
+static __always_inline bool hrtimer_test_and_clear_rearm_deferred_tif(unsigned long tif_work)
+{
+	lockdep_assert_irqs_disabled();
+
+	if (unlikely(tif_work & _TIF_HRTIMER_REARM)) {
+		clear_thread_flag(TIF_HRTIMER_REARM);
+		return true;
+	}
+	return false;
+}
+
+#define TIF_REARM_MASK	(_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY | _TIF_HRTIMER_REARM)
+
+/* Invoked from the exit to user before invoking exit_to_user_mode_loop() */
+static __always_inline bool
+hrtimer_rearm_deferred_user_irq(unsigned long *tif_work, const unsigned long tif_mask)
+{
+	/* Help the compiler to optimize the function out for syscall returns */
+	if (!(tif_mask & _TIF_HRTIMER_REARM))
+		return false;
+	/*
+	 * Rearm the timer if none of the resched flags is set before going into
+	 * the loop which re-enables interrupts.
+	 */
+	if (unlikely((*tif_work & TIF_REARM_MASK) == _TIF_HRTIMER_REARM)) {
+		clear_thread_flag(TIF_HRTIMER_REARM);
+		__hrtimer_rearm_deferred();
+		/* Don't go into the loop if HRTIMER_REARM was the only flag */
+		*tif_work &= ~TIF_HRTIMER_REARM;
+		return !*tif_work;
+	}
+	return false;
+}
+
+/* Invoked from the time slice extension decision function */
+static __always_inline void hrtimer_rearm_deferred_tif(unsigned long tif_work)
+{
+	if (hrtimer_test_and_clear_rearm_deferred_tif(tif_work))
+		__hrtimer_rearm_deferred();
+}
+
+/*
+ * This is to be called on all irqentry_exit() paths that will enable
+ * interrupts.
+ */
+static __always_inline void hrtimer_rearm_deferred(void)
+{
+	hrtimer_rearm_deferred_tif(read_thread_flags());
+}
+
+/*
+ * Invoked from the scheduler on entry to __schedule() so it can defer
+ * rearming after the load balancing callbacks which might change hrtick.
+ */
+static __always_inline bool hrtimer_test_and_clear_rearm_deferred(void)
+{
+	return hrtimer_test_and_clear_rearm_deferred_tif(read_thread_flags());
+}
+
+#else  /* CONFIG_HRTIMER_REARM_DEFERRED */
+static __always_inline void __hrtimer_rearm_deferred(void) { }
+static __always_inline void hrtimer_rearm_deferred(void) { }
+static __always_inline void hrtimer_rearm_deferred_tif(unsigned long tif_work) { }
+static __always_inline bool
+hrtimer_rearm_deferred_user_irq(unsigned long *tif_work, const unsigned long tif_mask) { return false; }
+static __always_inline bool hrtimer_test_and_clear_rearm_deferred(void) { return false; }
+#endif  /* !CONFIG_HRTIMER_REARM_DEFERRED */
+
+#endif