Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / kernel / time / tick-broadcast-hrtimer.c

diff --git a/kernel/kernel/time/tick-broadcast-hrtimer.c b/kernel/kernel/time/tick-broadcast-hrtimer.c
new file mode 100644 (file)
index 0000000..6aac4be
--- /dev/null
+++ b/kernel/kernel/time/tick-broadcast-hrtimer.c
@@ -0,0 +1,113 @@
+/*
+ * linux/kernel/time/tick-broadcast-hrtimer.c
+ * This file emulates a local clock event device
+ * via a pseudo clock device.
+ */
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/hrtimer.h>
+#include <linux/interrupt.h>
+#include <linux/percpu.h>
+#include <linux/profile.h>
+#include <linux/clockchips.h>
+#include <linux/sched.h>
+#include <linux/smp.h>
+#include <linux/module.h>
+
+#include "tick-internal.h"
+
+static struct hrtimer bctimer;
+
+static void bc_set_mode(enum clock_event_mode mode,
+                       struct clock_event_device *bc)
+{
+       switch (mode) {
+       case CLOCK_EVT_MODE_SHUTDOWN:
+               /*
+                * Note, we cannot cancel the timer here as we might
+                * run into the following live lock scenario:
+                *
+                * cpu 0                cpu1
+                * lock(broadcast_lock);
+                *                      hrtimer_interrupt()
+                *                      bc_handler()
+                *                         tick_handle_oneshot_broadcast();
+                *                          lock(broadcast_lock);
+                * hrtimer_cancel()
+                *  wait_for_callback()
+                */
+               hrtimer_try_to_cancel(&bctimer);
+               break;
+       default:
+               break;
+       }
+}
+
+/*
+ * This is called from the guts of the broadcast code when the cpu
+ * which is about to enter idle has the earliest broadcast timer event.
+ */
+static int bc_set_next(ktime_t expires, struct clock_event_device *bc)
+{
+       int bc_moved;
+       /*
+        * We try to cancel the timer first. If the callback is on
+        * flight on some other cpu then we let it handle it. If we
+        * were able to cancel the timer nothing can rearm it as we
+        * own broadcast_lock.
+        *
+        * However we can also be called from the event handler of
+        * ce_broadcast_hrtimer itself when it expires. We cannot
+        * restart the timer because we are in the callback, but we
+        * can set the expiry time and let the callback return
+        * HRTIMER_RESTART.
+        *
+        * Since we are in the idle loop at this point and because
+        * hrtimer_{start/cancel} functions call into tracing,
+        * calls to these functions must be bound within RCU_NONIDLE.
+        */
+       RCU_NONIDLE(bc_moved = (hrtimer_try_to_cancel(&bctimer) >= 0) ?
+               !hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED) :
+                       0);
+       if (bc_moved) {
+               /* Bind the "device" to the cpu */
+               bc->bound_on = smp_processor_id();
+       } else if (bc->bound_on == smp_processor_id()) {
+               hrtimer_set_expires(&bctimer, expires);
+       }
+       return 0;
+}
+
+static struct clock_event_device ce_broadcast_hrtimer = {
+       .set_mode               = bc_set_mode,
+       .set_next_ktime         = bc_set_next,
+       .features               = CLOCK_EVT_FEAT_ONESHOT |
+                                 CLOCK_EVT_FEAT_KTIME |
+                                 CLOCK_EVT_FEAT_HRTIMER,
+       .rating                 = 0,
+       .bound_on               = -1,
+       .min_delta_ns           = 1,
+       .max_delta_ns           = KTIME_MAX,
+       .min_delta_ticks        = 1,
+       .max_delta_ticks        = ULONG_MAX,
+       .mult                   = 1,
+       .shift                  = 0,
+       .cpumask                = cpu_all_mask,
+};
+
+static enum hrtimer_restart bc_handler(struct hrtimer *t)
+{
+       ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer);
+
+       if (ce_broadcast_hrtimer.next_event.tv64 == KTIME_MAX)
+               return HRTIMER_NORESTART;
+
+       return HRTIMER_RESTART;
+}
+
+void tick_setup_hrtimer_broadcast(void)
+{
+       hrtimer_init(&bctimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+       bctimer.function = bc_handler;
+       clockevents_register_device(&ce_broadcast_hrtimer);
+}