*
* Caller must disable preemption.
*/
-static void rcu_preempt_note_context_switch(int cpu)
+void rcu_preempt_note_context_switch(void)
{
struct task_struct *t = current;
unsigned long flags;
(t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
/* Possibly blocking in an RCU read-side critical section. */
- rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu);
+ rdp = __this_cpu_ptr(rcu_preempt_state.rda);
rnp = rdp->mynode;
raw_spin_lock_irqsave(&rnp->lock, flags);
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
* means that we continue to block the current grace period.
*/
local_irq_save(flags);
- rcu_preempt_qs(cpu);
+ rcu_preempt_qs(smp_processor_id());
local_irq_restore(flags);
}
rcu_init_one(&rcu_preempt_state, &rcu_preempt_data);
}
-/*
- * Check for a task exiting while in a preemptible-RCU read-side
- * critical section, clean up if so. No need to issue warnings,
- * as debug_check_no_locks_held() already does this if lockdep
- * is enabled.
- */
-void exit_rcu(void)
-{
- struct task_struct *t = current;
-
- if (t->rcu_read_lock_nesting == 0)
- return;
- t->rcu_read_lock_nesting = 1;
- __rcu_read_unlock();
-}
-
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
static struct rcu_state *rcu_state = &rcu_sched_state;
}
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
-/*
- * Because preemptible RCU does not exist, we never have to check for
- * CPUs being in quiescent states.
- */
-static void rcu_preempt_note_context_switch(int cpu)
-{
-}
-
/*
* Because preemptible RCU does not exist, there are never any preempted
* RCU readers.
{
}
+/*
+ * Don't bother keeping a running count of the number of RCU callbacks
+ * posted because CONFIG_RCU_FAST_NO_HZ=n.
+ */
+static void rcu_idle_count_callbacks_posted(void)
+{
+}
+
#else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */
/*
#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);
-static DEFINE_PER_CPU(struct hrtimer, rcu_idle_gp_timer);
-static ktime_t rcu_idle_gp_wait; /* If some non-lazy callbacks. */
-static ktime_t rcu_idle_lazy_gp_wait; /* If only lazy callbacks. */
+/* 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
*/
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;
rcu_preempt_cpu_has_nonlazy_callbacks(cpu);
}
+/*
+ * 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 enum hrtimer_restart rcu_idle_gp_timer_func(struct hrtimer *hrtp)
+static void rcu_idle_gp_timer_func(unsigned long cpu_in)
{
+ int cpu = (int)cpu_in;
+
trace_rcu_prep_idle("Timer");
- return HRTIMER_NORESTART;
+ 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... */
}
/*
*/
static void rcu_prepare_for_idle_init(int cpu)
{
- static int firsttime = 1;
- struct hrtimer *hrtp = &per_cpu(rcu_idle_gp_timer, cpu);
-
- hrtimer_init(hrtp, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
- hrtp->function = rcu_idle_gp_timer_func;
- if (firsttime) {
- unsigned int upj = jiffies_to_usecs(RCU_IDLE_GP_DELAY);
-
- rcu_idle_gp_wait = ns_to_ktime(upj * (u64)1000);
- upj = jiffies_to_usecs(RCU_IDLE_LAZY_GP_DELAY);
- rcu_idle_lazy_gp_wait = ns_to_ktime(upj * (u64)1000);
- firsttime = 0;
- }
+ 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;
}
/*
*/
static void rcu_cleanup_after_idle(int cpu)
{
- hrtimer_cancel(&per_cpu(rcu_idle_gp_timer, cpu));
+ del_timer(&per_cpu(rcu_idle_gp_timer, cpu));
+ trace_rcu_prep_idle("Cleanup after idle");
}
/*
*/
static void rcu_prepare_for_idle(int cpu)
{
+ struct timer_list *tp;
+
+ /*
+ * 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
+ * pending.
+ */
+ if (!per_cpu(rcu_idle_first_pass, cpu) &&
+ (per_cpu(rcu_nonlazy_posted, cpu) ==
+ per_cpu(rcu_nonlazy_posted_snap, cpu))) {
+ 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));
+ }
+ return;
+ }
+ per_cpu(rcu_idle_first_pass, cpu) = 0;
+ per_cpu(rcu_nonlazy_posted_snap, cpu) =
+ per_cpu(rcu_nonlazy_posted, cpu) - 1;
+
/*
* If there are no callbacks on this CPU, enter dyntick-idle mode.
* Also reset state to avoid prejudicing later attempts.
per_cpu(rcu_dyntick_drain, cpu) = 0;
per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
if (rcu_cpu_has_nonlazy_callbacks(cpu))
- hrtimer_start(&per_cpu(rcu_idle_gp_timer, cpu),
- rcu_idle_gp_wait, HRTIMER_MODE_REL);
+ per_cpu(rcu_idle_gp_timer_expires, cpu) =
+ jiffies + RCU_IDLE_GP_DELAY;
else
- hrtimer_start(&per_cpu(rcu_idle_gp_timer, cpu),
- rcu_idle_lazy_gp_wait, HRTIMER_MODE_REL);
+ per_cpu(rcu_idle_gp_timer_expires, cpu) =
+ 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);
return; /* Nothing more to do immediately. */
} else if (--per_cpu(rcu_dyntick_drain, cpu) <= 0) {
/* We have hit the limit, so time to give up. */
trace_rcu_prep_idle("Callbacks drained");
}
+/*
+ * Keep a running count of the number of non-lazy callbacks posted
+ * on this CPU. This running counter (which is never decremented) allows
+ * rcu_prepare_for_idle() to detect when something out of the idle loop
+ * posts a callback, even if an equal number of callbacks are invoked.
+ * Of course, callbacks should only be posted from within a trace event
+ * designed to be called from idle or from within RCU_NONIDLE().
+ */
+static void rcu_idle_count_callbacks_posted(void)
+{
+ __this_cpu_add(rcu_nonlazy_posted, 1);
+}
+
#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */
#ifdef CONFIG_RCU_CPU_STALL_INFO
static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
{
- struct hrtimer *hrtp = &per_cpu(rcu_idle_gp_timer, cpu);
+ struct timer_list *tltp = &per_cpu(rcu_idle_gp_timer, cpu);
- sprintf(cp, "drain=%d %c timer=%lld",
+ sprintf(cp, "drain=%d %c timer=%lu",
per_cpu(rcu_dyntick_drain, cpu),
per_cpu(rcu_dyntick_holdoff, cpu) == jiffies ? 'H' : '.',
- hrtimer_active(hrtp)
- ? ktime_to_us(hrtimer_get_remaining(hrtp))
- : -1);
+ timer_pending(tltp) ? tltp->expires - jiffies : -1);
}
#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */
projects / karo-tx-linux.git / blobdiff