diff options
| -rw-r--r-- | kernel/rcutree.c | 65 | ||||
| -rw-r--r-- | kernel/rcutree_plugin.h | 11 |
2 files changed, 22 insertions, 54 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 89419ff92e9..0a8ec5b2e20 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1635,6 +1635,20 @@ static int rcu_cpu_kthread(void *arg) * to manipulate rcu_cpu_kthread_task. There might be another CPU * attempting to access it during boot, but the locking in kthread_bind() * will enforce sufficient ordering. + * + * Please note that we cannot simply refuse to wake up the per-CPU + * kthread because kthreads are created in TASK_UNINTERRUPTIBLE state, + * which can result in softlockup complaints if the task ends up being + * idle for more than a couple of minutes. + * + * However, please note also that we cannot bind the per-CPU kthread to its + * CPU until that CPU is fully online. We also cannot wait until the + * CPU is fully online before we create its per-CPU kthread, as this would + * deadlock the system when CPU notifiers tried waiting for grace + * periods. So we bind the per-CPU kthread to its CPU only if the CPU + * is online. If its CPU is not yet fully online, then the code in + * rcu_cpu_kthread() will wait until it is fully online, and then do + * the binding. */ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu) { @@ -1647,12 +1661,14 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu) t = kthread_create(rcu_cpu_kthread, (void *)(long)cpu, "rcuc%d", cpu); if (IS_ERR(t)) return PTR_ERR(t); - kthread_bind(t, cpu); + if (cpu_online(cpu)) + kthread_bind(t, cpu); per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu; WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL); - per_cpu(rcu_cpu_kthread_task, cpu) = t; sp.sched_priority = RCU_KTHREAD_PRIO; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); + per_cpu(rcu_cpu_kthread_task, cpu) = t; + wake_up_process(t); /* Get to TASK_INTERRUPTIBLE quickly. */ return 0; } @@ -1759,12 +1775,11 @@ static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp, raw_spin_unlock_irqrestore(&rnp->lock, flags); sp.sched_priority = 99; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); + wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ } return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index); } -static void rcu_wake_one_boost_kthread(struct rcu_node *rnp); - /* * Spawn all kthreads -- called as soon as the scheduler is running. */ @@ -1772,30 +1787,18 @@ static int __init rcu_spawn_kthreads(void) { int cpu; struct rcu_node *rnp; - struct task_struct *t; rcu_kthreads_spawnable = 1; for_each_possible_cpu(cpu) { per_cpu(rcu_cpu_has_work, cpu) = 0; - if (cpu_online(cpu)) { + if (cpu_online(cpu)) (void)rcu_spawn_one_cpu_kthread(cpu); - t = per_cpu(rcu_cpu_kthread_task, cpu); - if (t) - wake_up_process(t); - } } rnp = rcu_get_root(rcu_state); (void)rcu_spawn_one_node_kthread(rcu_state, rnp); - if (rnp->node_kthread_task) - wake_up_process(rnp->node_kthread_task); if (NUM_RCU_NODES > 1) { - rcu_for_each_leaf_node(rcu_state, rnp) { + rcu_for_each_leaf_node(rcu_state, rnp) (void)rcu_spawn_one_node_kthread(rcu_state, rnp); - t = rnp->node_kthread_task; - if (t) - wake_up_process(t); - rcu_wake_one_boost_kthread(rnp); - } } return 0; } @@ -2221,31 +2224,6 @@ static void __cpuinit rcu_prepare_kthreads(int cpu) } /* - * kthread_create() creates threads in TASK_UNINTERRUPTIBLE state, - * but the RCU threads are woken on demand, and if demand is low this - * could be a while triggering the hung task watchdog. - * - * In order to avoid this, poke all tasks once the CPU is fully - * up and running. - */ -static void __cpuinit rcu_online_kthreads(int cpu) -{ - struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); - struct rcu_node *rnp = rdp->mynode; - struct task_struct *t; - - t = per_cpu(rcu_cpu_kthread_task, cpu); - if (t) - wake_up_process(t); - - t = rnp->node_kthread_task; - if (t) - wake_up_process(t); - - rcu_wake_one_boost_kthread(rnp); -} - -/* * Handle CPU online/offline notification events. */ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, @@ -2262,7 +2240,6 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, rcu_prepare_kthreads(cpu); break; case CPU_ONLINE: - rcu_online_kthreads(cpu); case CPU_DOWN_FAILED: rcu_node_kthread_setaffinity(rnp, -1); rcu_cpu_kthread_setrt(cpu, 1); diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index c8bff3099a8..ea2e2fb79e8 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -1299,15 +1299,10 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, raw_spin_unlock_irqrestore(&rnp->lock, flags); sp.sched_priority = RCU_KTHREAD_PRIO; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); + wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ return 0; } -static void __cpuinit rcu_wake_one_boost_kthread(struct rcu_node *rnp) -{ - if (rnp->boost_kthread_task) - wake_up_process(rnp->boost_kthread_task); -} - #else /* #ifdef CONFIG_RCU_BOOST */ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) @@ -1331,10 +1326,6 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, return 0; } -static void __cpuinit rcu_wake_one_boost_kthread(struct rcu_node *rnp) -{ -} - #endif /* #else #ifdef CONFIG_RCU_BOOST */ #ifndef CONFIG_SMP |