diff options
Diffstat (limited to 'kernel/rcutree_plugin.h')
| -rw-r--r-- | kernel/rcutree_plugin.h | 243 |
1 files changed, 149 insertions, 94 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index c023464816b..5271a020887 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -153,7 +153,7 @@ static void rcu_preempt_qs(int cpu) * * 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; @@ -164,7 +164,7 @@ static void rcu_preempt_note_context_switch(int cpu) (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; @@ -228,7 +228,7 @@ static void rcu_preempt_note_context_switch(int cpu) * 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); } @@ -969,22 +969,6 @@ static void __init __rcu_init_preempt(void) 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; @@ -1018,14 +1002,6 @@ void rcu_force_quiescent_state(void) 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. */ @@ -1910,8 +1886,9 @@ static void __cpuinit rcu_prepare_kthreads(int cpu) * 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); } @@ -1938,6 +1915,14 @@ static void rcu_prepare_for_idle(int cpu) { } +/* + * 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) */ /* @@ -1978,30 +1963,6 @@ static void rcu_prepare_for_idle(int cpu) #define RCU_IDLE_GP_DELAY 6 /* Roughly one grace period. */ #define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ -static DEFINE_PER_CPU(int, rcu_dyntick_drain); -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. */ - -/* - * 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) -{ - /* 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 @@ -2045,16 +2006,75 @@ static bool rcu_cpu_has_nonlazy_callbacks(int 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. + */ +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... */ } /* @@ -2062,29 +2082,25 @@ static enum hrtimer_restart rcu_idle_gp_timer_func(struct hrtimer *hrtp) */ 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); + struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); - 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; - } + 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) { - hrtimer_cancel(&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"); } /* @@ -2102,19 +2118,41 @@ static void rcu_cleanup_after_idle(int cpu) * 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 ->idle_gp_timer if this CPU has callbacks + * pending. + */ + 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); + } + 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 (!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; } @@ -2123,32 +2161,37 @@ static void rcu_prepare_for_idle(int cpu) * 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)) - hrtimer_start(&per_cpu(rcu_idle_gp_timer, cpu), - rcu_idle_gp_wait, HRTIMER_MODE_REL); - else - hrtimer_start(&per_cpu(rcu_idle_gp_timer, cpu), - rcu_idle_lazy_gp_wait, HRTIMER_MODE_REL); + 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 { + rdtp->idle_gp_timer_expires = + 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 (--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; @@ -2184,6 +2227,19 @@ static void rcu_prepare_for_idle(int cpu) 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_dynticks.nonlazy_posted, 1); +} + #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ #ifdef CONFIG_RCU_CPU_STALL_INFO @@ -2192,14 +2248,13 @@ static void rcu_prepare_for_idle(int cpu) static void print_cpu_stall_fast_no_hz(char *cp, int cpu) { - struct hrtimer *hrtp = &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=%lld", - 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); + sprintf(cp, "drain=%d %c timer=%lu", + rdtp->dyntick_drain, + rdtp->dyntick_holdoff == jiffies ? 'H' : '.', + timer_pending(tltp) ? tltp->expires - jiffies : -1); } #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ |