diff options
Diffstat (limited to 'kernel/rcutree_plugin.h')
-rw-r--r-- | kernel/rcutree_plugin.h | 191 |
1 files changed, 137 insertions, 54 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 4778936..c0cb783 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -64,22 +64,31 @@ EXPORT_SYMBOL_GPL(rcu_batches_completed); * not in a quiescent state. There might be any number of tasks blocked * while in an RCU read-side critical section. */ -static void rcu_preempt_qs_record(int cpu) +static void rcu_preempt_qs(int cpu) { struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); - rdp->passed_quiesc = 1; rdp->passed_quiesc_completed = rdp->completed; + barrier(); + rdp->passed_quiesc = 1; } /* - * We have entered the scheduler or are between softirqs in ksoftirqd. - * If we are in an RCU read-side critical section, we need to reflect - * that in the state of the rcu_node structure corresponding to this CPU. - * Caller must disable hardirqs. + * We have entered the scheduler, and the current task might soon be + * context-switched away from. If this task is in an RCU read-side + * critical section, we will no longer be able to rely on the CPU to + * record that fact, so we enqueue the task on the appropriate entry + * of the blocked_tasks[] array. The task will dequeue itself when + * it exits the outermost enclosing RCU read-side critical section. + * Therefore, the current grace period cannot be permitted to complete + * until the blocked_tasks[] entry indexed by the low-order bit of + * rnp->gpnum empties. + * + * Caller must disable preemption. */ -static void rcu_preempt_qs(int cpu) +static void rcu_preempt_note_context_switch(int cpu) { struct task_struct *t = current; + unsigned long flags; int phase; struct rcu_data *rdp; struct rcu_node *rnp; @@ -90,7 +99,7 @@ static void rcu_preempt_qs(int cpu) /* Possibly blocking in an RCU read-side critical section. */ rdp = rcu_preempt_state.rda[cpu]; rnp = rdp->mynode; - spin_lock(&rnp->lock); + spin_lock_irqsave(&rnp->lock, flags); t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; t->rcu_blocked_node = rnp; @@ -103,11 +112,15 @@ static void rcu_preempt_qs(int cpu) * state for the current grace period), then as long * as that task remains queued, the current grace period * cannot end. + * + * But first, note that the current CPU must still be + * on line! */ - phase = !(rnp->qsmask & rdp->grpmask) ^ (rnp->gpnum & 0x1); + WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0); + WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); + phase = (rnp->gpnum + !(rnp->qsmask & rdp->grpmask)) & 0x1; list_add(&t->rcu_node_entry, &rnp->blocked_tasks[phase]); - smp_mb(); /* Ensure later ctxt swtch seen after above. */ - spin_unlock(&rnp->lock); + spin_unlock_irqrestore(&rnp->lock, flags); } /* @@ -119,9 +132,10 @@ static void rcu_preempt_qs(int cpu) * grace period, then the fact that the task has been enqueued * means that we continue to block the current grace period. */ - rcu_preempt_qs_record(cpu); - t->rcu_read_unlock_special &= ~(RCU_READ_UNLOCK_NEED_QS | - RCU_READ_UNLOCK_GOT_QS); + rcu_preempt_qs(cpu); + local_irq_save(flags); + t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; + local_irq_restore(flags); } /* @@ -136,6 +150,16 @@ void __rcu_read_lock(void) } EXPORT_SYMBOL_GPL(__rcu_read_lock); +/* + * Check for preempted RCU readers blocking the current grace period + * for the specified rcu_node structure. If the caller needs a reliable + * answer, it must hold the rcu_node's ->lock. + */ +static int rcu_preempted_readers(struct rcu_node *rnp) +{ + return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]); +} + static void rcu_read_unlock_special(struct task_struct *t) { int empty; @@ -157,7 +181,7 @@ static void rcu_read_unlock_special(struct task_struct *t) special = t->rcu_read_unlock_special; if (special & RCU_READ_UNLOCK_NEED_QS) { t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; - t->rcu_read_unlock_special |= RCU_READ_UNLOCK_GOT_QS; + rcu_preempt_qs(smp_processor_id()); } /* Hardware IRQ handlers cannot block. */ @@ -177,12 +201,12 @@ static void rcu_read_unlock_special(struct task_struct *t) */ for (;;) { rnp = t->rcu_blocked_node; - spin_lock(&rnp->lock); + spin_lock(&rnp->lock); /* irqs already disabled. */ if (rnp == t->rcu_blocked_node) break; - spin_unlock(&rnp->lock); + spin_unlock(&rnp->lock); /* irqs remain disabled. */ } - empty = list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]); + empty = !rcu_preempted_readers(rnp); list_del_init(&t->rcu_node_entry); t->rcu_blocked_node = NULL; @@ -193,10 +217,9 @@ static void rcu_read_unlock_special(struct task_struct *t) * drop rnp->lock and restore irq. */ if (!empty && rnp->qsmask == 0 && - list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1])) { - t->rcu_read_unlock_special &= - ~(RCU_READ_UNLOCK_NEED_QS | - RCU_READ_UNLOCK_GOT_QS); + !rcu_preempted_readers(rnp)) { + struct rcu_node *rnp_p; + if (rnp->parent == NULL) { /* Only one rcu_node in the tree. */ cpu_quiet_msk_finish(&rcu_preempt_state, flags); @@ -205,9 +228,10 @@ static void rcu_read_unlock_special(struct task_struct *t) /* Report up the rest of the hierarchy. */ mask = rnp->grpmask; spin_unlock_irqrestore(&rnp->lock, flags); - rnp = rnp->parent; - spin_lock_irqsave(&rnp->lock, flags); - cpu_quiet_msk(mask, &rcu_preempt_state, rnp, flags); + rnp_p = rnp->parent; + spin_lock_irqsave(&rnp_p->lock, flags); + WARN_ON_ONCE(rnp->qsmask); + cpu_quiet_msk(mask, &rcu_preempt_state, rnp_p, flags); return; } spin_unlock(&rnp->lock); @@ -243,12 +267,12 @@ static void rcu_print_task_stall(struct rcu_node *rnp) { unsigned long flags; struct list_head *lp; - int phase = rnp->gpnum & 0x1; + int phase; struct task_struct *t; - if (!list_empty(&rnp->blocked_tasks[phase])) { + if (rcu_preempted_readers(rnp)) { spin_lock_irqsave(&rnp->lock, flags); - phase = rnp->gpnum & 0x1; /* re-read under lock. */ + phase = rnp->gpnum & 0x1; lp = &rnp->blocked_tasks[phase]; list_for_each_entry(t, lp, rcu_node_entry) printk(" P%d", t->pid); @@ -259,13 +283,16 @@ static void rcu_print_task_stall(struct rcu_node *rnp) #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ /* - * Check for preempted RCU readers for the specified rcu_node structure. - * If the caller needs a reliable answer, it must hold the rcu_node's - * >lock. + * Check that the list of blocked tasks for the newly completed grace + * period is in fact empty. It is a serious bug to complete a grace + * period that still has RCU readers blocked! This function must be + * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock + * must be held by the caller. */ -static int rcu_preempted_readers(struct rcu_node *rnp) +static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { - return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]); + WARN_ON_ONCE(rcu_preempted_readers(rnp)); + WARN_ON_ONCE(rnp->qsmask); } #ifdef CONFIG_HOTPLUG_CPU @@ -280,7 +307,8 @@ static int rcu_preempted_readers(struct rcu_node *rnp) * The caller must hold rnp->lock with irqs disabled. */ static void rcu_preempt_offline_tasks(struct rcu_state *rsp, - struct rcu_node *rnp) + struct rcu_node *rnp, + struct rcu_data *rdp) { int i; struct list_head *lp; @@ -292,6 +320,9 @@ static void rcu_preempt_offline_tasks(struct rcu_state *rsp, WARN_ONCE(1, "Last CPU thought to be offlined?"); return; /* Shouldn't happen: at least one CPU online. */ } + WARN_ON_ONCE(rnp != rdp->mynode && + (!list_empty(&rnp->blocked_tasks[0]) || + !list_empty(&rnp->blocked_tasks[1]))); /* * Move tasks up to root rcu_node. Rely on the fact that the @@ -335,20 +366,12 @@ static void rcu_preempt_check_callbacks(int cpu) struct task_struct *t = current; if (t->rcu_read_lock_nesting == 0) { - t->rcu_read_unlock_special &= - ~(RCU_READ_UNLOCK_NEED_QS | RCU_READ_UNLOCK_GOT_QS); - rcu_preempt_qs_record(cpu); + t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; + rcu_preempt_qs(cpu); return; } - if (per_cpu(rcu_preempt_data, cpu).qs_pending) { - if (t->rcu_read_unlock_special & RCU_READ_UNLOCK_GOT_QS) { - rcu_preempt_qs_record(cpu); - t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_GOT_QS; - } else if (!(t->rcu_read_unlock_special & - RCU_READ_UNLOCK_NEED_QS)) { - t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; - } - } + if (per_cpu(rcu_preempt_data, cpu).qs_pending) + t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; } /* @@ -387,6 +410,15 @@ static int rcu_preempt_needs_cpu(int cpu) return !!per_cpu(rcu_preempt_data, cpu).nxtlist; } +/** + * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. + */ +void rcu_barrier(void) +{ + _rcu_barrier(&rcu_preempt_state, call_rcu); +} +EXPORT_SYMBOL_GPL(rcu_barrier); + /* * Initialize preemptable RCU's per-CPU data. */ @@ -396,6 +428,22 @@ static void __cpuinit rcu_preempt_init_percpu_data(int cpu) } /* + * Move preemptable RCU's callbacks to ->orphan_cbs_list. + */ +static void rcu_preempt_send_cbs_to_orphanage(void) +{ + rcu_send_cbs_to_orphanage(&rcu_preempt_state); +} + +/* + * Initialize preemptable RCU's state structures. + */ +static void __init __rcu_init_preempt(void) +{ + RCU_INIT_FLAVOR(&rcu_preempt_state, rcu_preempt_data); +} + +/* * Check for a task exiting while in a preemptable-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 @@ -434,8 +482,17 @@ EXPORT_SYMBOL_GPL(rcu_batches_completed); * Because preemptable RCU does not exist, we never have to check for * CPUs being in quiescent states. */ -static void rcu_preempt_qs(int cpu) +static void rcu_preempt_note_context_switch(int cpu) +{ +} + +/* + * Because preemptable RCU does not exist, there are never any preempted + * RCU readers. + */ +static int rcu_preempted_readers(struct rcu_node *rnp) { + return 0; } #ifdef CONFIG_RCU_CPU_STALL_DETECTOR @@ -451,12 +508,13 @@ static void rcu_print_task_stall(struct rcu_node *rnp) #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ /* - * Because preemptable RCU does not exist, there are never any preempted - * RCU readers. + * Because there is no preemptable RCU, there can be no readers blocked, + * so there is no need to check for blocked tasks. So check only for + * bogus qsmask values. */ -static int rcu_preempted_readers(struct rcu_node *rnp) +static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { - return 0; + WARN_ON_ONCE(rnp->qsmask); } #ifdef CONFIG_HOTPLUG_CPU @@ -466,7 +524,8 @@ static int rcu_preempted_readers(struct rcu_node *rnp) * tasks that were blocked within RCU read-side critical sections. */ static void rcu_preempt_offline_tasks(struct rcu_state *rsp, - struct rcu_node *rnp) + struct rcu_node *rnp, + struct rcu_data *rdp) { } @@ -484,7 +543,7 @@ static void rcu_preempt_offline_cpu(int cpu) * Because preemptable RCU does not exist, it never has any callbacks * to check. */ -void rcu_preempt_check_callbacks(int cpu) +static void rcu_preempt_check_callbacks(int cpu) { } @@ -492,7 +551,7 @@ void rcu_preempt_check_callbacks(int cpu) * Because preemptable RCU does not exist, it never has any callbacks * to process. */ -void rcu_preempt_process_callbacks(void) +static void rcu_preempt_process_callbacks(void) { } @@ -522,6 +581,16 @@ static int rcu_preempt_needs_cpu(int cpu) } /* + * Because preemptable RCU does not exist, rcu_barrier() is just + * another name for rcu_barrier_sched(). + */ +void rcu_barrier(void) +{ + rcu_barrier_sched(); +} +EXPORT_SYMBOL_GPL(rcu_barrier); + +/* * Because preemptable RCU does not exist, there is no per-CPU * data to initialize. */ @@ -529,4 +598,18 @@ static void __cpuinit rcu_preempt_init_percpu_data(int cpu) { } +/* + * Because there is no preemptable RCU, there are no callbacks to move. + */ +static void rcu_preempt_send_cbs_to_orphanage(void) +{ +} + +/* + * Because preemptable RCU does not exist, it need not be initialized. + */ +static void __init __rcu_init_preempt(void) +{ +} + #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ |