* Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs
* any flavor of RCU.
*/
-int rcu_needs_cpu(int cpu)
+int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
{
+ *delta_jiffies = ULONG_MAX;
return rcu_cpu_has_callbacks(cpu);
}
#define RCU_IDLE_GP_DELAY 6 /* Roughly one grace period. */
#define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */
-/* Loop counter for rcu_prepare_for_idle(). */
-static DEFINE_PER_CPU(int, rcu_dyntick_drain);
-/* If rcu_dyntick_holdoff==jiffies, don't try to enter dyntick-idle mode. */
-static DEFINE_PER_CPU(unsigned long, rcu_dyntick_holdoff);
-/* Timer to awaken the CPU if it enters dyntick-idle mode with callbacks. */
-static DEFINE_PER_CPU(struct timer_list, rcu_idle_gp_timer);
-/* Scheduled expiry time for rcu_idle_gp_timer to allow reposting. */
-static DEFINE_PER_CPU(unsigned long, rcu_idle_gp_timer_expires);
-/* Enable special processing on first attempt to enter dyntick-idle mode. */
-static DEFINE_PER_CPU(bool, rcu_idle_first_pass);
-/* Running count of non-lazy callbacks posted, never decremented. */
-static DEFINE_PER_CPU(unsigned long, rcu_nonlazy_posted);
-/* Snapshot of rcu_nonlazy_posted to detect meaningful exits from idle. */
-static DEFINE_PER_CPU(unsigned long, rcu_nonlazy_posted_snap);
-
-/*
- * Allow the CPU to enter dyntick-idle mode if either: (1) There are no
- * callbacks on this CPU, (2) this CPU has not yet attempted to enter
- * dyntick-idle mode, or (3) this CPU is in the process of attempting to
- * enter dyntick-idle mode. Otherwise, if we have recently tried and failed
- * to enter dyntick-idle mode, we refuse to try to enter it. After all,
- * it is better to incur scheduling-clock interrupts than to spin
- * continuously for the same time duration!
- */
-int rcu_needs_cpu(int cpu)
-{
- /* Flag a new idle sojourn to the idle-entry state machine. */
- per_cpu(rcu_idle_first_pass, cpu) = 1;
- /* If no callbacks, RCU doesn't need the CPU. */
- if (!rcu_cpu_has_callbacks(cpu))
- return 0;
- /* Otherwise, RCU needs the CPU only if it recently tried and failed. */
- return per_cpu(rcu_dyntick_holdoff, cpu) == jiffies;
-}
-
/*
* Does the specified flavor of RCU have non-lazy callbacks pending on
* the specified CPU? Both RCU flavor and CPU are specified by the
rcu_preempt_cpu_has_nonlazy_callbacks(cpu);
}
+/*
+ * Allow the CPU to enter dyntick-idle mode if either: (1) There are no
+ * callbacks on this CPU, (2) this CPU has not yet attempted to enter
+ * dyntick-idle mode, or (3) this CPU is in the process of attempting to
+ * enter dyntick-idle mode. Otherwise, if we have recently tried and failed
+ * to enter dyntick-idle mode, we refuse to try to enter it. After all,
+ * it is better to incur scheduling-clock interrupts than to spin
+ * continuously for the same time duration!
+ *
+ * The delta_jiffies argument is used to store the time when RCU is
+ * going to need the CPU again if it still has callbacks. The reason
+ * for this is that rcu_prepare_for_idle() might need to post a timer,
+ * but if so, it will do so after tick_nohz_stop_sched_tick() has set
+ * the wakeup time for this CPU. This means that RCU's timer can be
+ * delayed until the wakeup time, which defeats the purpose of posting
+ * a timer.
+ */
+int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
+{
+ struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+
+ /* Flag a new idle sojourn to the idle-entry state machine. */
+ rdtp->idle_first_pass = 1;
+ /* If no callbacks, RCU doesn't need the CPU. */
+ if (!rcu_cpu_has_callbacks(cpu)) {
+ *delta_jiffies = ULONG_MAX;
+ return 0;
+ }
+ if (rdtp->dyntick_holdoff == jiffies) {
+ /* RCU recently tried and failed, so don't try again. */
+ *delta_jiffies = 1;
+ return 1;
+ }
+ /* Set up for the possibility that RCU will post a timer. */
+ if (rcu_cpu_has_nonlazy_callbacks(cpu))
+ *delta_jiffies = RCU_IDLE_GP_DELAY;
+ else
+ *delta_jiffies = RCU_IDLE_LAZY_GP_DELAY;
+ return 0;
+}
+
/*
* Handler for smp_call_function_single(). The only point of this
* handler is to wake the CPU up, so the handler does only tracing.
*/
static void rcu_prepare_for_idle_init(int cpu)
{
- per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
- setup_timer(&per_cpu(rcu_idle_gp_timer, cpu),
- rcu_idle_gp_timer_func, cpu);
- per_cpu(rcu_idle_gp_timer_expires, cpu) = jiffies - 1;
- per_cpu(rcu_idle_first_pass, cpu) = 1;
+ struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+
+ rdtp->dyntick_holdoff = jiffies - 1;
+ setup_timer(&rdtp->idle_gp_timer, rcu_idle_gp_timer_func, cpu);
+ rdtp->idle_gp_timer_expires = jiffies - 1;
+ rdtp->idle_first_pass = 1;
}
/*
* Clean up for exit from idle. Because we are exiting from idle, there
- * is no longer any point to rcu_idle_gp_timer, so cancel it. This will
+ * is no longer any point to ->idle_gp_timer, so cancel it. This will
* do nothing if this timer is not active, so just cancel it unconditionally.
*/
static void rcu_cleanup_after_idle(int cpu)
{
- del_timer(&per_cpu(rcu_idle_gp_timer, cpu));
+ struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+
+ del_timer(&rdtp->idle_gp_timer);
trace_rcu_prep_idle("Cleanup after idle");
}
* Because it is not legal to invoke rcu_process_callbacks() with irqs
* disabled, we do one pass of force_quiescent_state(), then do a
* invoke_rcu_core() to cause rcu_process_callbacks() to be invoked
- * later. The per-cpu rcu_dyntick_drain variable controls the sequencing.
+ * later. The ->dyntick_drain field controls the sequencing.
*
* The caller must have disabled interrupts.
*/
static void rcu_prepare_for_idle(int cpu)
{
struct timer_list *tp;
+ struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
/*
* If this is an idle re-entry, for example, due to use of
* RCU_NONIDLE() or the new idle-loop tracing API within the idle
* loop, then don't take any state-machine actions, unless the
* momentary exit from idle queued additional non-lazy callbacks.
- * Instead, repost the rcu_idle_gp_timer if this CPU has callbacks
+ * Instead, repost the ->idle_gp_timer if this CPU has callbacks
* pending.
*/
- if (!per_cpu(rcu_idle_first_pass, cpu) &&
- (per_cpu(rcu_nonlazy_posted, cpu) ==
- per_cpu(rcu_nonlazy_posted_snap, cpu))) {
+ if (!rdtp->idle_first_pass &&
+ (rdtp->nonlazy_posted == rdtp->nonlazy_posted_snap)) {
if (rcu_cpu_has_callbacks(cpu)) {
- tp = &per_cpu(rcu_idle_gp_timer, cpu);
- mod_timer_pinned(tp, per_cpu(rcu_idle_gp_timer_expires, cpu));
+ tp = &rdtp->idle_gp_timer;
+ mod_timer_pinned(tp, rdtp->idle_gp_timer_expires);
}
return;
}
- per_cpu(rcu_idle_first_pass, cpu) = 0;
- per_cpu(rcu_nonlazy_posted_snap, cpu) =
- per_cpu(rcu_nonlazy_posted, cpu) - 1;
+ rdtp->idle_first_pass = 0;
+ rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted - 1;
/*
* If there are no callbacks on this CPU, enter dyntick-idle mode.
* Also reset state to avoid prejudicing later attempts.
*/
if (!rcu_cpu_has_callbacks(cpu)) {
- per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
- per_cpu(rcu_dyntick_drain, cpu) = 0;
+ rdtp->dyntick_holdoff = jiffies - 1;
+ rdtp->dyntick_drain = 0;
trace_rcu_prep_idle("No callbacks");
return;
}
* If in holdoff mode, just return. We will presumably have
* refrained from disabling the scheduling-clock tick.
*/
- if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies) {
+ if (rdtp->dyntick_holdoff == jiffies) {
trace_rcu_prep_idle("In holdoff");
return;
}
- /* Check and update the rcu_dyntick_drain sequencing. */
- if (per_cpu(rcu_dyntick_drain, cpu) <= 0) {
+ /* Check and update the ->dyntick_drain sequencing. */
+ if (rdtp->dyntick_drain <= 0) {
/* First time through, initialize the counter. */
- per_cpu(rcu_dyntick_drain, cpu) = RCU_IDLE_FLUSHES;
- } else if (per_cpu(rcu_dyntick_drain, cpu) <= RCU_IDLE_OPT_FLUSHES &&
+ rdtp->dyntick_drain = RCU_IDLE_FLUSHES;
+ } else if (rdtp->dyntick_drain <= RCU_IDLE_OPT_FLUSHES &&
!rcu_pending(cpu) &&
!local_softirq_pending()) {
/* Can we go dyntick-idle despite still having callbacks? */
- trace_rcu_prep_idle("Dyntick with callbacks");
- per_cpu(rcu_dyntick_drain, cpu) = 0;
- per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
- if (rcu_cpu_has_nonlazy_callbacks(cpu))
- per_cpu(rcu_idle_gp_timer_expires, cpu) =
+ rdtp->dyntick_drain = 0;
+ rdtp->dyntick_holdoff = jiffies;
+ if (rcu_cpu_has_nonlazy_callbacks(cpu)) {
+ trace_rcu_prep_idle("Dyntick with callbacks");
+ rdtp->idle_gp_timer_expires =
jiffies + RCU_IDLE_GP_DELAY;
- else
- per_cpu(rcu_idle_gp_timer_expires, cpu) =
+ } else {
+ rdtp->idle_gp_timer_expires =
jiffies + RCU_IDLE_LAZY_GP_DELAY;
- tp = &per_cpu(rcu_idle_gp_timer, cpu);
- mod_timer_pinned(tp, per_cpu(rcu_idle_gp_timer_expires, cpu));
- per_cpu(rcu_nonlazy_posted_snap, cpu) =
- per_cpu(rcu_nonlazy_posted, cpu);
+ trace_rcu_prep_idle("Dyntick with lazy callbacks");
+ }
+ tp = &rdtp->idle_gp_timer;
+ mod_timer_pinned(tp, rdtp->idle_gp_timer_expires);
+ rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted;
return; /* Nothing more to do immediately. */
- } else if (--per_cpu(rcu_dyntick_drain, cpu) <= 0) {
+ } else if (--(rdtp->dyntick_drain) <= 0) {
/* We have hit the limit, so time to give up. */
- per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
+ rdtp->dyntick_holdoff = jiffies;
trace_rcu_prep_idle("Begin holdoff");
invoke_rcu_core(); /* Force the CPU out of dyntick-idle. */
return;
*/
static void rcu_idle_count_callbacks_posted(void)
{
- __this_cpu_add(rcu_nonlazy_posted, 1);
+ __this_cpu_add(rcu_dynticks.nonlazy_posted, 1);
}
#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */
static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
{
- struct timer_list *tltp = &per_cpu(rcu_idle_gp_timer, cpu);
+ struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+ struct timer_list *tltp = &rdtp->idle_gp_timer;
sprintf(cp, "drain=%d %c timer=%lu",
- per_cpu(rcu_dyntick_drain, cpu),
- per_cpu(rcu_dyntick_holdoff, cpu) == jiffies ? 'H' : '.',
+ rdtp->dyntick_drain,
+ rdtp->dyntick_holdoff == jiffies ? 'H' : '.',
timer_pending(tltp) ? tltp->expires - jiffies : -1);
}
projects / ~andy / linux / blobdiff