diff options
| -rw-r--r-- | kernel/rcutree.c | 40 | ||||
| -rw-r--r-- | kernel/rcutree.h | 3 | ||||
| -rw-r--r-- | kernel/rcutree_plugin.h | 85 |
3 files changed, 85 insertions, 43 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 9b36d6d7fb97..b79bfcd28e95 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -51,7 +51,7 @@ /* Data structures. */ -static struct lock_class_key rcu_root_class; +static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; #define RCU_STATE_INITIALIZER(name) { \ .level = { &name.node[0] }, \ @@ -936,6 +936,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) { unsigned long flags; unsigned long mask; + int need_quiet = 0; struct rcu_data *rdp = rsp->rda[cpu]; struct rcu_node *rnp; @@ -949,29 +950,30 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) spin_lock(&rnp->lock); /* irqs already disabled. */ rnp->qsmaskinit &= ~mask; if (rnp->qsmaskinit != 0) { - spin_unlock(&rnp->lock); /* irqs remain disabled. */ + if (rnp != rdp->mynode) + spin_unlock(&rnp->lock); /* irqs remain disabled. */ break; } - - /* - * If there was a task blocking the current grace period, - * and if all CPUs have checked in, we need to propagate - * the quiescent state up the rcu_node hierarchy. But that - * is inconvenient at the moment due to deadlock issues if - * this should end the current grace period. So set the - * offlined CPU's bit in ->qsmask in order to force the - * next force_quiescent_state() invocation to clean up this - * mess in a deadlock-free manner. - */ - if (rcu_preempt_offline_tasks(rsp, rnp, rdp) && !rnp->qsmask) - rnp->qsmask |= mask; - + if (rnp == rdp->mynode) + need_quiet = rcu_preempt_offline_tasks(rsp, rnp, rdp); + else + spin_unlock(&rnp->lock); /* irqs remain disabled. */ mask = rnp->grpmask; - spin_unlock(&rnp->lock); /* irqs remain disabled. */ rnp = rnp->parent; } while (rnp != NULL); - spin_unlock_irqrestore(&rsp->onofflock, flags); + /* + * We still hold the leaf rcu_node structure lock here, and + * irqs are still disabled. The reason for this subterfuge is + * because invoking task_quiet() with ->onofflock held leads + * to deadlock. + */ + spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ + rnp = rdp->mynode; + if (need_quiet) + task_quiet(rnp, flags); + else + spin_unlock_irqrestore(&rnp->lock, flags); rcu_adopt_orphan_cbs(rsp); } @@ -1731,6 +1733,7 @@ static void __init rcu_init_one(struct rcu_state *rsp) rnp = rsp->level[i]; for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { spin_lock_init(&rnp->lock); + lockdep_set_class(&rnp->lock, &rcu_node_class[i]); rnp->gpnum = 0; rnp->qsmask = 0; rnp->qsmaskinit = 0; @@ -1753,7 +1756,6 @@ static void __init rcu_init_one(struct rcu_state *rsp) INIT_LIST_HEAD(&rnp->blocked_tasks[1]); } } - lockdep_set_class(&rcu_get_root(rsp)->lock, &rcu_root_class); } /* diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 17a28a08b559..a81188c42929 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -305,6 +305,9 @@ static void rcu_bootup_announce(void); long rcu_batches_completed(void); static void rcu_preempt_note_context_switch(int cpu); static int rcu_preempted_readers(struct rcu_node *rnp); +#ifdef CONFIG_HOTPLUG_CPU +static void task_quiet(struct rcu_node *rnp, unsigned long flags); +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ #ifdef CONFIG_RCU_CPU_STALL_DETECTOR static void rcu_print_task_stall(struct rcu_node *rnp); #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 5ca2d26c5971..0bdb592eee66 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -160,11 +160,51 @@ static int rcu_preempted_readers(struct rcu_node *rnp) return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]); } +/* + * Record a quiescent state for all tasks that were previously queued + * on the specified rcu_node structure and that were blocking the current + * RCU grace period. The caller must hold the specified rnp->lock with + * irqs disabled, and this lock is released upon return, but irqs remain + * disabled. + */ +static void task_quiet(struct rcu_node *rnp, unsigned long flags) + __releases(rnp->lock) +{ + unsigned long mask; + struct rcu_node *rnp_p; + + if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) { + spin_unlock_irqrestore(&rnp->lock, flags); + return; /* Still need more quiescent states! */ + } + + rnp_p = rnp->parent; + if (rnp_p == NULL) { + /* + * Either there is only one rcu_node in the tree, + * or tasks were kicked up to root rcu_node due to + * CPUs going offline. + */ + cpu_quiet_msk_finish(&rcu_preempt_state, flags); + return; + } + + /* Report up the rest of the hierarchy. */ + mask = rnp->grpmask; + spin_unlock(&rnp->lock); /* irqs remain disabled. */ + spin_lock(&rnp_p->lock); /* irqs already disabled. */ + cpu_quiet_msk(mask, &rcu_preempt_state, rnp_p, flags); +} + +/* + * Handle special cases during rcu_read_unlock(), such as needing to + * notify RCU core processing or task having blocked during the RCU + * read-side critical section. + */ static void rcu_read_unlock_special(struct task_struct *t) { int empty; unsigned long flags; - unsigned long mask; struct rcu_node *rnp; int special; @@ -213,30 +253,15 @@ static void rcu_read_unlock_special(struct task_struct *t) /* * If this was the last task on the current list, and if * we aren't waiting on any CPUs, report the quiescent state. - * Note that both cpu_quiet_msk_finish() and cpu_quiet_msk() - * drop rnp->lock and restore irq. + * Note that task_quiet() releases rnp->lock. */ - if (!empty && rnp->qsmask == 0 && - !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); - return; - } - /* Report up the rest of the hierarchy. */ - mask = rnp->grpmask; + if (empty) spin_unlock_irqrestore(&rnp->lock, 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); + else + task_quiet(rnp, flags); + } else { + local_irq_restore(flags); } - local_irq_restore(flags); } /* @@ -303,6 +328,8 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) * rcu_node. The reason for not just moving them to the immediate * parent is to remove the need for rcu_read_unlock_special() to * make more than two attempts to acquire the target rcu_node's lock. + * Returns true if there were tasks blocking the current RCU grace + * period. * * Returns 1 if there was previously a task blocking the current grace * period on the specified rcu_node structure. @@ -316,7 +343,7 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp, int i; struct list_head *lp; struct list_head *lp_root; - int retval = rcu_preempted_readers(rnp); + int retval; struct rcu_node *rnp_root = rcu_get_root(rsp); struct task_struct *tp; @@ -334,6 +361,7 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp, * rcu_nodes in terms of gp_num value. This fact allows us to * move the blocked_tasks[] array directly, element by element. */ + retval = rcu_preempted_readers(rnp); for (i = 0; i < 2; i++) { lp = &rnp->blocked_tasks[i]; lp_root = &rnp_root->blocked_tasks[i]; @@ -346,7 +374,6 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp, spin_unlock(&rnp_root->lock); /* irqs remain disabled */ } } - return retval; } @@ -512,6 +539,16 @@ static int rcu_preempted_readers(struct rcu_node *rnp) return 0; } +#ifdef CONFIG_HOTPLUG_CPU + +/* Because preemptible RCU does not exist, no quieting of tasks. */ +static void task_quiet(struct rcu_node *rnp, unsigned long flags) +{ + spin_unlock_irqrestore(&rnp->lock, flags); +} + +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ + #ifdef CONFIG_RCU_CPU_STALL_DETECTOR /* |