int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
{
*delta_jiffies = ULONG_MAX;
- return rcu_cpu_has_callbacks(cpu);
-}
-
-/*
- * Because we do not have RCU_FAST_NO_HZ, don't bother initializing for it.
- */
-static void rcu_prepare_for_idle_init(int cpu)
-{
+ return rcu_cpu_has_callbacks(cpu, NULL);
}
/*
*
* The following three proprocessor symbols control this state machine:
*
- * RCU_IDLE_FLUSHES gives the maximum number of times that we will attempt
- * to satisfy RCU. Beyond this point, it is better to incur a periodic
- * scheduling-clock interrupt than to loop through the state machine
- * at full power.
- * RCU_IDLE_OPT_FLUSHES gives the number of RCU_IDLE_FLUSHES that are
- * optional if RCU does not need anything immediately from this
- * CPU, even if this CPU still has RCU callbacks queued. The first
- * times through the state machine are mandatory: we need to give
- * the state machine a chance to communicate a quiescent state
- * to the RCU core.
* RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted
* to sleep in dyntick-idle mode with RCU callbacks pending. This
* is sized to be roughly one RCU grace period. Those energy-efficiency
* adjustment, they can be converted into kernel config parameters, though
* making the state machine smarter might be a better option.
*/
-#define RCU_IDLE_FLUSHES 5 /* Number of dyntick-idle tries. */
-#define RCU_IDLE_OPT_FLUSHES 3 /* Optional dyntick-idle tries. */
#define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */
#define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */
-static int rcu_idle_flushes = RCU_IDLE_FLUSHES;
-module_param(rcu_idle_flushes, int, 0644);
-static int rcu_idle_opt_flushes = RCU_IDLE_OPT_FLUSHES;
-module_param(rcu_idle_opt_flushes, int, 0644);
static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY;
module_param(rcu_idle_gp_delay, int, 0644);
static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY;
extern int tick_nohz_enabled;
/*
- * 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_data structure.
- */
-static bool __rcu_cpu_has_nonlazy_callbacks(struct rcu_data *rdp)
-{
- return rdp->qlen != rdp->qlen_lazy;
-}
-
-#ifdef CONFIG_TREE_PREEMPT_RCU
-
-/*
- * Are there non-lazy RCU-preempt callbacks? (There cannot be if there
- * is no RCU-preempt in the kernel.)
+ * Try to advance callbacks for all flavors of RCU on the current CPU.
+ * Afterwards, if there are any callbacks ready for immediate invocation,
+ * return true.
*/
-static bool rcu_preempt_cpu_has_nonlazy_callbacks(int cpu)
+static bool rcu_try_advance_all_cbs(void)
{
- struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu);
-
- return __rcu_cpu_has_nonlazy_callbacks(rdp);
-}
-
-#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+ bool cbs_ready = false;
+ struct rcu_data *rdp;
+ struct rcu_node *rnp;
+ struct rcu_state *rsp;
-static bool rcu_preempt_cpu_has_nonlazy_callbacks(int cpu)
-{
- return 0;
-}
+ for_each_rcu_flavor(rsp) {
+ rdp = this_cpu_ptr(rsp->rda);
+ rnp = rdp->mynode;
-#endif /* else #ifdef CONFIG_TREE_PREEMPT_RCU */
+ /*
+ * Don't bother checking unless a grace period has
+ * completed since we last checked and there are
+ * callbacks not yet ready to invoke.
+ */
+ if (rdp->completed != rnp->completed &&
+ rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL])
+ rcu_process_gp_end(rsp, rdp);
-/*
- * Does any flavor of RCU have non-lazy callbacks on the specified CPU?
- */
-static bool rcu_cpu_has_nonlazy_callbacks(int cpu)
-{
- return __rcu_cpu_has_nonlazy_callbacks(&per_cpu(rcu_sched_data, cpu)) ||
- __rcu_cpu_has_nonlazy_callbacks(&per_cpu(rcu_bh_data, cpu)) ||
- rcu_preempt_cpu_has_nonlazy_callbacks(cpu);
+ if (cpu_has_callbacks_ready_to_invoke(rdp))
+ cbs_ready = true;
+ }
+ return cbs_ready;
}
/*
- * 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!
+ * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready
+ * to invoke. If the CPU has callbacks, try to advance them. Tell the
+ * caller to set the timeout based on whether or not there are non-lazy
+ * callbacks.
*
- * 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.
+ * The caller must have disabled interrupts.
*/
-int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
+int rcu_needs_cpu(int cpu, unsigned long *dj)
{
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;
+ /* Snapshot to detect later posting of non-lazy callback. */
+ rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted;
+
/* If no callbacks, RCU doesn't need the CPU. */
- if (!rcu_cpu_has_callbacks(cpu)) {
- *delta_jiffies = ULONG_MAX;
+ if (!rcu_cpu_has_callbacks(cpu, &rdtp->all_lazy)) {
+ *dj = ULONG_MAX;
return 0;
}
- if (rdtp->dyntick_holdoff == jiffies) {
- /* RCU recently tried and failed, so don't try again. */
- *delta_jiffies = 1;
+
+ /* Attempt to advance callbacks. */
+ if (rcu_try_advance_all_cbs()) {
+ /* Some ready to invoke, so initiate later invocation. */
+ invoke_rcu_core();
return 1;
}
- /* Set up for the possibility that RCU will post a timer. */
- if (rcu_cpu_has_nonlazy_callbacks(cpu)) {
- *delta_jiffies = round_up(rcu_idle_gp_delay + jiffies,
- rcu_idle_gp_delay) - jiffies;
+ rdtp->last_accelerate = jiffies;
+
+ /* Request timer delay depending on laziness, and round. */
+ if (rdtp->all_lazy) {
+ *dj = round_up(rcu_idle_gp_delay + jiffies,
+ rcu_idle_gp_delay) - jiffies;
} else {
- *delta_jiffies = jiffies + rcu_idle_lazy_gp_delay;
- *delta_jiffies = round_jiffies(*delta_jiffies) - jiffies;
+ *dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies;
}
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.
- */
-void rcu_idle_demigrate(void *unused)
-{
- trace_rcu_prep_idle("Demigrate");
-}
-
-/*
- * Timer handler used to force CPU to start pushing its remaining RCU
- * callbacks in the case where it entered dyntick-idle mode with callbacks
- * pending. The hander doesn't really need to do anything because the
- * real work is done upon re-entry to idle, or by the next scheduling-clock
- * interrupt should idle not be re-entered.
- *
- * One special case: the timer gets migrated without awakening the CPU
- * on which the timer was scheduled on. In this case, we must wake up
- * that CPU. We do so with smp_call_function_single().
- */
-static void rcu_idle_gp_timer_func(unsigned long cpu_in)
-{
- int cpu = (int)cpu_in;
-
- trace_rcu_prep_idle("Timer");
- if (cpu != smp_processor_id())
- smp_call_function_single(cpu, rcu_idle_demigrate, NULL, 0);
- else
- WARN_ON_ONCE(1); /* Getting here can hang the system... */
-}
-
-/*
- * Initialize the timer used to pull CPUs out of dyntick-idle mode.
- */
-static void rcu_prepare_for_idle_init(int cpu)
-{
- 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 ->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)
-{
- struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
-
- del_timer(&rdtp->idle_gp_timer);
- trace_rcu_prep_idle("Cleanup after idle");
- rdtp->tick_nohz_enabled_snap = ACCESS_ONCE(tick_nohz_enabled);
-}
-
-/*
- * Check to see if any RCU-related work can be done by the current CPU,
- * and if so, schedule a softirq to get it done. This function is part
- * of the RCU implementation; it is -not- an exported member of the RCU API.
- *
- * The idea is for the current CPU to clear out all work required by the
- * RCU core for the current grace period, so that this CPU can be permitted
- * to enter dyntick-idle mode. In some cases, it will need to be awakened
- * at the end of the grace period by whatever CPU ends the grace period.
- * This allows CPUs to go dyntick-idle more quickly, and to reduce the
- * number of wakeups by a modest integer factor.
- *
- * 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 ->dyntick_drain field controls the sequencing.
+ * Prepare a CPU for idle from an RCU perspective. The first major task
+ * is to sense whether nohz mode has been enabled or disabled via sysfs.
+ * The second major task is to check to see if a non-lazy callback has
+ * arrived at a CPU that previously had only lazy callbacks. The third
+ * major task is to accelerate (that is, assign grace-period numbers to)
+ * any recently arrived callbacks.
*
* The caller must have disabled interrupts.
*/
static void rcu_prepare_for_idle(int cpu)
{
- struct timer_list *tp;
+ struct rcu_data *rdp;
struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+ struct rcu_node *rnp;
+ struct rcu_state *rsp;
int tne;
/* Handle nohz enablement switches conservatively. */
tne = ACCESS_ONCE(tick_nohz_enabled);
if (tne != rdtp->tick_nohz_enabled_snap) {
- if (rcu_cpu_has_callbacks(cpu))
+ if (rcu_cpu_has_callbacks(cpu, NULL))
invoke_rcu_core(); /* force nohz to see update. */
rdtp->tick_nohz_enabled_snap = tne;
return;
if (!tne)
return;
- /* Adaptive-tick mode, where usermode execution is idle to RCU. */
- if (!is_idle_task(current)) {
- rdtp->dyntick_holdoff = jiffies - 1;
- if (rcu_cpu_has_nonlazy_callbacks(cpu)) {
- trace_rcu_prep_idle("User dyntick with callbacks");
- rdtp->idle_gp_timer_expires =
- round_up(jiffies + rcu_idle_gp_delay,
- rcu_idle_gp_delay);
- } else if (rcu_cpu_has_callbacks(cpu)) {
- rdtp->idle_gp_timer_expires =
- round_jiffies(jiffies + rcu_idle_lazy_gp_delay);
- trace_rcu_prep_idle("User dyntick with lazy callbacks");
- } else {
- return;
- }
- tp = &rdtp->idle_gp_timer;
- mod_timer_pinned(tp, rdtp->idle_gp_timer_expires);
+ /* If this is a no-CBs CPU, no callbacks, just return. */
+ if (is_nocb_cpu(cpu))
return;
- }
/*
- * 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 ->idle_gp_timer if this CPU has callbacks
- * pending.
+ * If a non-lazy callback arrived at a CPU having only lazy
+ * callbacks, invoke RCU core for the side-effect of recalculating
+ * idle duration on re-entry to idle.
*/
- if (!rdtp->idle_first_pass &&
- (rdtp->nonlazy_posted == rdtp->nonlazy_posted_snap)) {
- if (rcu_cpu_has_callbacks(cpu)) {
- tp = &rdtp->idle_gp_timer;
- mod_timer_pinned(tp, rdtp->idle_gp_timer_expires);
- }
+ if (rdtp->all_lazy &&
+ rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) {
+ invoke_rcu_core();
return;
}
- 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 we have not yet accelerated this jiffy, accelerate all
+ * callbacks on this CPU.
*/
- if (!rcu_cpu_has_callbacks(cpu)) {
- rdtp->dyntick_holdoff = jiffies - 1;
- rdtp->dyntick_drain = 0;
- trace_rcu_prep_idle("No callbacks");
+ if (rdtp->last_accelerate == jiffies)
return;
+ rdtp->last_accelerate = jiffies;
+ for_each_rcu_flavor(rsp) {
+ rdp = per_cpu_ptr(rsp->rda, cpu);
+ if (!*rdp->nxttail[RCU_DONE_TAIL])
+ continue;
+ rnp = rdp->mynode;
+ raw_spin_lock(&rnp->lock); /* irqs already disabled. */
+ rcu_accelerate_cbs(rsp, rnp, rdp);
+ raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
+}
- /*
- * If in holdoff mode, just return. We will presumably have
- * refrained from disabling the scheduling-clock tick.
- */
- if (rdtp->dyntick_holdoff == jiffies) {
- trace_rcu_prep_idle("In holdoff");
- return;
- }
+/*
+ * Clean up for exit from idle. Attempt to advance callbacks based on
+ * any grace periods that elapsed while the CPU was idle, and if any
+ * callbacks are now ready to invoke, initiate invocation.
+ */
+static void rcu_cleanup_after_idle(int cpu)
+{
+ struct rcu_data *rdp;
+ struct rcu_state *rsp;
- /* Check and update the ->dyntick_drain sequencing. */
- if (rdtp->dyntick_drain <= 0) {
- /* First time through, initialize the counter. */
- 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? */
- 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 =
- round_up(jiffies + rcu_idle_gp_delay,
- rcu_idle_gp_delay);
- } else {
- rdtp->idle_gp_timer_expires =
- round_jiffies(jiffies + rcu_idle_lazy_gp_delay);
- 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 (--(rdtp->dyntick_drain) <= 0) {
- /* We have hit the limit, so time to give up. */
- rdtp->dyntick_holdoff = jiffies;
- trace_rcu_prep_idle("Begin holdoff");
- invoke_rcu_core(); /* Force the CPU out of dyntick-idle. */
+ if (is_nocb_cpu(cpu))
return;
- }
-
- /*
- * Do one step of pushing the remaining RCU callbacks through
- * the RCU core state machine.
- */
-#ifdef CONFIG_TREE_PREEMPT_RCU
- if (per_cpu(rcu_preempt_data, cpu).nxtlist) {
- rcu_preempt_qs(cpu);
- force_quiescent_state(&rcu_preempt_state);
- }
-#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
- if (per_cpu(rcu_sched_data, cpu).nxtlist) {
- rcu_sched_qs(cpu);
- force_quiescent_state(&rcu_sched_state);
- }
- if (per_cpu(rcu_bh_data, cpu).nxtlist) {
- rcu_bh_qs(cpu);
- force_quiescent_state(&rcu_bh_state);
- }
-
- /*
- * If RCU callbacks are still pending, RCU still needs this CPU.
- * So try forcing the callbacks through the grace period.
- */
- if (rcu_cpu_has_callbacks(cpu)) {
- trace_rcu_prep_idle("More callbacks");
- invoke_rcu_core();
- } else {
- trace_rcu_prep_idle("Callbacks drained");
+ rcu_try_advance_all_cbs();
+ for_each_rcu_flavor(rsp) {
+ rdp = per_cpu_ptr(rsp->rda, cpu);
+ if (cpu_has_callbacks_ready_to_invoke(rdp))
+ invoke_rcu_core();
}
}
static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
{
struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
- struct timer_list *tltp = &rdtp->idle_gp_timer;
- char c;
+ unsigned long nlpd = rdtp->nonlazy_posted - rdtp->nonlazy_posted_snap;
- c = rdtp->dyntick_holdoff == jiffies ? 'H' : '.';
- if (timer_pending(tltp))
- sprintf(cp, "drain=%d %c timer=%lu",
- rdtp->dyntick_drain, c, tltp->expires - jiffies);
- else
- sprintf(cp, "drain=%d %c timer not pending",
- rdtp->dyntick_drain, c);
+ sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c",
+ rdtp->last_accelerate & 0xffff, jiffies & 0xffff,
+ ulong2long(nlpd),
+ rdtp->all_lazy ? 'L' : '.',
+ rdtp->tick_nohz_enabled_snap ? '.' : 'D');
}
#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */
projects / GitHub / mt8127 / android_kernel_alcatel_ttab.git / blobdiff