+static void __call_rcu(struct rcu_head *head, struct rcu_ctrlblk *rcp,
+ struct rcu_data *rdp)
+{
+ long batch;
+
+ head->next = NULL;
+ smp_mb(); /* Read of rcu->cur must happen after any change by caller. */
+
+ /*
+ * Determine the batch number of this callback.
+ *
+ * Using ACCESS_ONCE to avoid the following error when gcc eliminates
+ * local variable "batch" and emits codes like this:
+ * 1) rdp->batch = rcp->cur + 1 # gets old value
+ * ......
+ * 2)rcu_batch_after(rcp->cur + 1, rdp->batch) # gets new value
+ * then [*nxttail[0], *nxttail[1]) may contain callbacks
+ * that batch# = rdp->batch, see the comment of struct rcu_data.
+ */
+ batch = ACCESS_ONCE(rcp->cur) + 1;
+
+ if (rdp->nxtlist && rcu_batch_after(batch, rdp->batch)) {
+ /* process callbacks */
+ rdp->nxttail[0] = rdp->nxttail[1];
+ rdp->nxttail[1] = rdp->nxttail[2];
+ if (rcu_batch_after(batch - 1, rdp->batch))
+ rdp->nxttail[0] = rdp->nxttail[2];
+ }
+
+ rdp->batch = batch;
+ *rdp->nxttail[2] = head;
+ rdp->nxttail[2] = &head->next;
+
+ if (unlikely(++rdp->qlen > qhimark)) {
+ rdp->blimit = INT_MAX;
+ force_quiescent_state(rdp, &rcu_ctrlblk);
+ }
+}
+
+#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
+
+static void record_gp_stall_check_time(struct rcu_ctrlblk *rcp)
+{
+ rcp->gp_start = jiffies;
+ rcp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK;
+}
+
+static void print_other_cpu_stall(struct rcu_ctrlblk *rcp)
+{
+ int cpu;
+ long delta;
+ unsigned long flags;
+
+ /* Only let one CPU complain about others per time interval. */
+
+ spin_lock_irqsave(&rcp->lock, flags);
+ delta = jiffies - rcp->jiffies_stall;
+ if (delta < 2 || rcp->cur != rcp->completed) {
+ spin_unlock_irqrestore(&rcp->lock, flags);
+ return;
+ }
+ rcp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
+ spin_unlock_irqrestore(&rcp->lock, flags);
+
+ /* OK, time to rat on our buddy... */
+
+ printk(KERN_ERR "INFO: RCU detected CPU stalls:");
+ for_each_possible_cpu(cpu) {
+ if (cpumask_test_cpu(cpu, to_cpumask(rcp->cpumask)))
+ printk(" %d", cpu);
+ }
+ printk(" (detected by %d, t=%ld jiffies)\n",
+ smp_processor_id(), (long)(jiffies - rcp->gp_start));
+}
+
+static void print_cpu_stall(struct rcu_ctrlblk *rcp)
+{
+ unsigned long flags;
+
+ printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu/%lu jiffies)\n",
+ smp_processor_id(), jiffies,
+ jiffies - rcp->gp_start);
+ dump_stack();
+ spin_lock_irqsave(&rcp->lock, flags);
+ if ((long)(jiffies - rcp->jiffies_stall) >= 0)
+ rcp->jiffies_stall =
+ jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
+ spin_unlock_irqrestore(&rcp->lock, flags);
+ set_need_resched(); /* kick ourselves to get things going. */
+}
+
+static void check_cpu_stall(struct rcu_ctrlblk *rcp)
+{
+ long delta;
+
+ delta = jiffies - rcp->jiffies_stall;
+ if (cpumask_test_cpu(smp_processor_id(), to_cpumask(rcp->cpumask)) &&
+ delta >= 0) {
+
+ /* We haven't checked in, so go dump stack. */
+ print_cpu_stall(rcp);
+
+ } else if (rcp->cur != rcp->completed && delta >= 2) {
+
+ /* They had two seconds to dump stack, so complain. */
+ print_other_cpu_stall(rcp);
+ }
+}
+
+#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
+
+static void record_gp_stall_check_time(struct rcu_ctrlblk *rcp)
+{
+}
+
+static inline void check_cpu_stall(struct rcu_ctrlblk *rcp)
+{
+}
+
+#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
+