diff options
| -rw-r--r-- | kernel/rcutree.c | 190 | ||||
| -rw-r--r-- | kernel/rcutree.h | 3 |
2 files changed, 129 insertions, 64 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index f7bcd9e6c054..4792f1642bf2 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1042,6 +1042,102 @@ rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_dat } /* + * Body of kthread that handles grace periods. + */ +static int rcu_gp_kthread(void *arg) +{ + struct rcu_data *rdp; + struct rcu_node *rnp; + struct rcu_state *rsp = arg; + + for (;;) { + + /* Handle grace-period start. */ + rnp = rcu_get_root(rsp); + for (;;) { + wait_event_interruptible(rsp->gp_wq, rsp->gp_flags); + if (rsp->gp_flags) + break; + flush_signals(current); + } + raw_spin_lock_irq(&rnp->lock); + rsp->gp_flags = 0; + rdp = this_cpu_ptr(rsp->rda); + + if (rcu_gp_in_progress(rsp)) { + /* + * A grace period is already in progress, so + * don't start another one. + */ + raw_spin_unlock_irq(&rnp->lock); + continue; + } + + if (rsp->fqs_active) { + /* + * We need a grace period, but force_quiescent_state() + * is running. Tell it to start one on our behalf. + */ + rsp->fqs_need_gp = 1; + raw_spin_unlock_irq(&rnp->lock); + continue; + } + + /* Advance to a new grace period and initialize state. */ + rsp->gpnum++; + trace_rcu_grace_period(rsp->name, rsp->gpnum, "start"); + WARN_ON_ONCE(rsp->fqs_state == RCU_GP_INIT); + rsp->fqs_state = RCU_GP_INIT; /* Stop force_quiescent_state. */ + rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; + record_gp_stall_check_time(rsp); + raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ + + /* Exclude any concurrent CPU-hotplug operations. */ + raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ + + /* + * Set the quiescent-state-needed bits in all the rcu_node + * structures for all currently online CPUs in breadth-first + * order, starting from the root rcu_node structure. + * This operation relies on the layout of the hierarchy + * within the rsp->node[] array. Note that other CPUs will + * access only the leaves of the hierarchy, which still + * indicate that no grace period is in progress, at least + * until the corresponding leaf node has been initialized. + * In addition, we have excluded CPU-hotplug operations. + * + * Note that the grace period cannot complete until + * we finish the initialization process, as there will + * be at least one qsmask bit set in the root node until + * that time, namely the one corresponding to this CPU, + * due to the fact that we have irqs disabled. + */ + rcu_for_each_node_breadth_first(rsp, rnp) { + raw_spin_lock(&rnp->lock); /* irqs already disabled. */ + rcu_preempt_check_blocked_tasks(rnp); + rnp->qsmask = rnp->qsmaskinit; + rnp->gpnum = rsp->gpnum; + rnp->completed = rsp->completed; + if (rnp == rdp->mynode) + rcu_start_gp_per_cpu(rsp, rnp, rdp); + rcu_preempt_boost_start_gp(rnp); + trace_rcu_grace_period_init(rsp->name, rnp->gpnum, + rnp->level, rnp->grplo, + rnp->grphi, rnp->qsmask); + raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ + } + + rnp = rcu_get_root(rsp); + raw_spin_lock(&rnp->lock); /* irqs already disabled. */ + /* force_quiescent_state() now OK. */ + rsp->fqs_state = RCU_SIGNAL_INIT; + raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ + raw_spin_unlock_irq(&rsp->onofflock); + } + return 0; +} + +/* * Start a new RCU grace period if warranted, re-initializing the hierarchy * in preparation for detecting the next grace period. The caller must hold * the root node's ->lock, which is released before return. Hard irqs must @@ -1058,77 +1154,20 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) struct rcu_data *rdp = this_cpu_ptr(rsp->rda); struct rcu_node *rnp = rcu_get_root(rsp); - if (!rcu_scheduler_fully_active || + if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { /* - * Either the scheduler hasn't yet spawned the first - * non-idle task or this CPU does not need another - * grace period. Either way, don't start a new grace - * period. + * Either we have not yet spawned the grace-period + * task or this CPU does not need another grace period. + * Either way, don't start a new grace period. */ raw_spin_unlock_irqrestore(&rnp->lock, flags); return; } - if (rsp->fqs_active) { - /* - * This CPU needs a grace period, but force_quiescent_state() - * is running. Tell it to start one on this CPU's behalf. - */ - rsp->fqs_need_gp = 1; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - - /* Advance to a new grace period and initialize state. */ - rsp->gpnum++; - trace_rcu_grace_period(rsp->name, rsp->gpnum, "start"); - WARN_ON_ONCE(rsp->fqs_state == RCU_GP_INIT); - rsp->fqs_state = RCU_GP_INIT; /* Hold off force_quiescent_state. */ - rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; - record_gp_stall_check_time(rsp); - raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ - - /* Exclude any concurrent CPU-hotplug operations. */ - raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ - - /* - * Set the quiescent-state-needed bits in all the rcu_node - * structures for all currently online CPUs in breadth-first - * order, starting from the root rcu_node structure. This - * operation relies on the layout of the hierarchy within the - * rsp->node[] array. Note that other CPUs will access only - * the leaves of the hierarchy, which still indicate that no - * grace period is in progress, at least until the corresponding - * leaf node has been initialized. In addition, we have excluded - * CPU-hotplug operations. - * - * Note that the grace period cannot complete until we finish - * the initialization process, as there will be at least one - * qsmask bit set in the root node until that time, namely the - * one corresponding to this CPU, due to the fact that we have - * irqs disabled. - */ - rcu_for_each_node_breadth_first(rsp, rnp) { - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - rcu_preempt_check_blocked_tasks(rnp); - rnp->qsmask = rnp->qsmaskinit; - rnp->gpnum = rsp->gpnum; - rnp->completed = rsp->completed; - if (rnp == rdp->mynode) - rcu_start_gp_per_cpu(rsp, rnp, rdp); - rcu_preempt_boost_start_gp(rnp); - trace_rcu_grace_period_init(rsp->name, rnp->gpnum, - rnp->level, rnp->grplo, - rnp->grphi, rnp->qsmask); - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - } - - rnp = rcu_get_root(rsp); - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ - rsp->fqs_state = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ - raw_spin_unlock_irqrestore(&rsp->onofflock, flags); + rsp->gp_flags = 1; + raw_spin_unlock_irqrestore(&rnp->lock, flags); + wake_up(&rsp->gp_wq); } /* @@ -2629,6 +2668,28 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, } /* + * Spawn the kthread that handles this RCU flavor's grace periods. + */ +static int __init rcu_spawn_gp_kthread(void) +{ + unsigned long flags; + struct rcu_node *rnp; + struct rcu_state *rsp; + struct task_struct *t; + + for_each_rcu_flavor(rsp) { + t = kthread_run(rcu_gp_kthread, rsp, rsp->name); + BUG_ON(IS_ERR(t)); + rnp = rcu_get_root(rsp); + raw_spin_lock_irqsave(&rnp->lock, flags); + rsp->gp_kthread = t; + raw_spin_unlock_irqrestore(&rnp->lock, flags); + } + return 0; +} +early_initcall(rcu_spawn_gp_kthread); + +/* * This function is invoked towards the end of the scheduler's initialization * process. Before this is called, the idle task might contain * RCU read-side critical sections (during which time, this idle @@ -2729,6 +2790,7 @@ static void __init rcu_init_one(struct rcu_state *rsp, } rsp->rda = rda; + init_waitqueue_head(&rsp->gp_wq); rnp = rsp->level[rcu_num_lvls - 1]; for_each_possible_cpu(i) { while (i > rnp->grphi) diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 4d29169f2124..117a15019e99 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -385,6 +385,9 @@ struct rcu_state { u8 boost; /* Subject to priority boost. */ unsigned long gpnum; /* Current gp number. */ unsigned long completed; /* # of last completed gp. */ + struct task_struct *gp_kthread; /* Task for grace periods. */ + wait_queue_head_t gp_wq; /* Where GP task waits. */ + int gp_flags; /* Commands for GP task. */ /* End of fields guarded by root rcu_node's lock. */ |