#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
+#ifdef CONFIG_RCU_CPU_STALL_VERBOSE
+
+/*
+ * Dump detailed information for all tasks blocking the current RCU
+ * grace period on the specified rcu_node structure.
+ */
+static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)
+{
+ unsigned long flags;
+ struct list_head *lp;
+ int phase;
+ struct task_struct *t;
+
+ if (rcu_preempted_readers(rnp)) {
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ phase = rnp->gpnum & 0x1;
+ lp = &rnp->blocked_tasks[phase];
+ list_for_each_entry(t, lp, rcu_node_entry)
+ sched_show_task(t);
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ }
+}
+
+/*
+ * Dump detailed information for all tasks blocking the current RCU
+ * grace period.
+ */
+static void rcu_print_detail_task_stall(struct rcu_state *rsp)
+{
+ struct rcu_node *rnp = rcu_get_root(rsp);
+
+ rcu_print_detail_task_stall_rnp(rnp);
+ rcu_for_each_leaf_node(rsp, rnp)
+ rcu_print_detail_task_stall_rnp(rnp);
+}
+
+#else /* #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */
+
+static void rcu_print_detail_task_stall(struct rcu_state *rsp)
+{
+}
+
+#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */
+
/*
* Scan the current list of tasks blocked within RCU read-side critical
* sections, printing out the tid of each.
*/
static void rcu_print_task_stall(struct rcu_node *rnp)
{
- unsigned long flags;
struct list_head *lp;
int phase;
struct task_struct *t;
if (rcu_preempted_readers(rnp)) {
- raw_spin_lock_irqsave(&rnp->lock, flags);
phase = rnp->gpnum & 0x1;
lp = &rnp->blocked_tasks[phase];
list_for_each_entry(t, lp, rcu_node_entry)
printk(" P%d", t->pid);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
}
* Because preemptable RCU does not exist, we never have to check for
* tasks blocked within RCU read-side critical sections.
*/
+static void rcu_print_detail_task_stall(struct rcu_state *rsp)
+{
+}
+
+/*
+ * Because preemptable RCU does not exist, we never have to check for
+ * tasks blocked within RCU read-side critical sections.
+ */
static void rcu_print_task_stall(struct rcu_node *rnp)
{
}
return rcu_needs_cpu_quick_check(cpu);
}
+/*
+ * Check to see if we need to continue a callback-flush operations to
+ * allow the last CPU to enter dyntick-idle mode. But fast dyntick-idle
+ * entry is not configured, so we never do need to.
+ */
+static void rcu_needs_cpu_flush(void)
+{
+}
+
#else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */
#define RCU_NEEDS_CPU_FLUSHES 5
+static DEFINE_PER_CPU(int, rcu_dyntick_drain);
+static DEFINE_PER_CPU(unsigned long, rcu_dyntick_holdoff);
/*
* Check to see if any future RCU-related work will need to be done
* only if all other CPUs are already in dynticks-idle mode. This will
* allow the CPU cores to be powered down immediately, as opposed to after
* waiting many milliseconds for grace periods to elapse.
+ *
+ * Because it is not legal to invoke rcu_process_callbacks() with irqs
+ * disabled, we do one pass of force_quiescent_state(), then do a
+ * raise_softirq() to cause rcu_process_callbacks() to be invoked later.
+ * The per-cpu rcu_dyntick_drain variable controls the sequencing.
*/
int rcu_needs_cpu(int cpu)
{
- int c = 1;
- int i;
+ int c = 0;
int thatcpu;
+ /* Check for being in the holdoff period. */
+ if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies)
+ return rcu_needs_cpu_quick_check(cpu);
+
/* Don't bother unless we are the last non-dyntick-idle CPU. */
for_each_cpu_not(thatcpu, nohz_cpu_mask)
- if (thatcpu != cpu)
+ if (thatcpu != cpu) {
+ per_cpu(rcu_dyntick_drain, cpu) = 0;
+ per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
return rcu_needs_cpu_quick_check(cpu);
-
- /* Try to push remaining RCU-sched and RCU-bh callbacks through. */
- for (i = 0; i < RCU_NEEDS_CPU_FLUSHES && c; i++) {
- c = 0;
- if (per_cpu(rcu_sched_data, cpu).nxtlist) {
- rcu_sched_qs(cpu);
- force_quiescent_state(&rcu_sched_state, 0);
- __rcu_process_callbacks(&rcu_sched_state,
- &per_cpu(rcu_sched_data, cpu));
- c = !!per_cpu(rcu_sched_data, cpu).nxtlist;
- }
- if (per_cpu(rcu_bh_data, cpu).nxtlist) {
- rcu_bh_qs(cpu);
- force_quiescent_state(&rcu_bh_state, 0);
- __rcu_process_callbacks(&rcu_bh_state,
- &per_cpu(rcu_bh_data, cpu));
- c = !!per_cpu(rcu_bh_data, cpu).nxtlist;
}
+
+ /* Check and update the rcu_dyntick_drain sequencing. */
+ if (per_cpu(rcu_dyntick_drain, cpu) <= 0) {
+ /* First time through, initialize the counter. */
+ per_cpu(rcu_dyntick_drain, cpu) = RCU_NEEDS_CPU_FLUSHES;
+ } else if (--per_cpu(rcu_dyntick_drain, cpu) <= 0) {
+ /* We have hit the limit, so time to give up. */
+ per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
+ return rcu_needs_cpu_quick_check(cpu);
+ }
+
+ /* Do one step pushing remaining RCU callbacks through. */
+ if (per_cpu(rcu_sched_data, cpu).nxtlist) {
+ rcu_sched_qs(cpu);
+ force_quiescent_state(&rcu_sched_state, 0);
+ c = c || per_cpu(rcu_sched_data, cpu).nxtlist;
+ }
+ if (per_cpu(rcu_bh_data, cpu).nxtlist) {
+ rcu_bh_qs(cpu);
+ force_quiescent_state(&rcu_bh_state, 0);
+ c = c || per_cpu(rcu_bh_data, cpu).nxtlist;
}
/* If RCU callbacks are still pending, RCU still needs this CPU. */
+ if (c)
+ raise_softirq(RCU_SOFTIRQ);
return c;
}
+/*
+ * Check to see if we need to continue a callback-flush operations to
+ * allow the last CPU to enter dyntick-idle mode.
+ */
+static void rcu_needs_cpu_flush(void)
+{
+ int cpu = smp_processor_id();
+ unsigned long flags;
+
+ if (per_cpu(rcu_dyntick_drain, cpu) <= 0)
+ return;
+ local_irq_save(flags);
+ (void)rcu_needs_cpu(cpu);
+ local_irq_restore(flags);
+}
+
#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */