+static bool update_needs_ipi(struct hrtimer_cpu_base *cpu_base,
+ unsigned int active)
+{
+ struct hrtimer_clock_base *base;
+ unsigned int seq;
+ ktime_t expires;
+
+ /*
+ * Update the base offsets unconditionally so the following
+ * checks whether the SMP function call is required works.
+ *
+ * The update is safe even when the remote CPU is in the hrtimer
+ * interrupt or the hrtimer soft interrupt and expiring affected
+ * bases. Either it will see the update before handling a base or
+ * it will see it when it finishes the processing and reevaluates
+ * the next expiring timer.
+ */
+ seq = cpu_base->clock_was_set_seq;
+ hrtimer_update_base(cpu_base);
+
+ /*
+ * If the sequence did not change over the update then the
+ * remote CPU already handled it.
+ */
+ if (seq == cpu_base->clock_was_set_seq)
+ return false;
+
+ /*
+ * If the remote CPU is currently handling an hrtimer interrupt, it
+ * will reevaluate the first expiring timer of all clock bases
+ * before reprogramming. Nothing to do here.
+ */
+ if (cpu_base->in_hrtirq)
+ return false;
+
+ /*
+ * Walk the affected clock bases and check whether the first expiring
+ * timer in a clock base is moving ahead of the first expiring timer of
+ * @cpu_base. If so, the IPI must be invoked because per CPU clock
+ * event devices cannot be remotely reprogrammed.
+ */
+ active &= cpu_base->active_bases;
+
+ for_each_active_base(base, cpu_base, active) {
+ struct timerqueue_node *next;
+
+ next = timerqueue_getnext(&base->active);
+ expires = ktime_sub(next->expires, base->offset);
+ if (expires < cpu_base->expires_next)
+ return true;
+
+ /* Extra check for softirq clock bases */
+ if (base->clockid < HRTIMER_BASE_MONOTONIC_SOFT)
+ continue;
+ if (cpu_base->softirq_activated)
+ continue;
+ if (expires < cpu_base->softirq_expires_next)
+ return true;
+ }
+ return false;
+}
+