diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2009-09-11 13:20:18 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-09-11 13:20:18 -0700 |
commit | eee2775d9924b22643bd89b2e568cc5eed7e8a04 (patch) | |
tree | 095ad7851895c5d39596f3ff7ee1e078235a2501 /kernel/rcutree_plugin.h | |
parent | 53e16fbd30005905168d9b75555fdc7e0a2eac58 (diff) | |
parent | 7db905e636f08ea5bc9825c1f73d77802e8ccad5 (diff) |
Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (28 commits)
rcu: Move end of special early-boot RCU operation earlier
rcu: Changes from reviews: avoid casts, fix/add warnings, improve comments
rcu: Create rcutree plugins to handle hotplug CPU for multi-level trees
rcu: Remove lockdep annotations from RCU's _notrace() API members
rcu: Add #ifdef to suppress __rcu_offline_cpu() warning in !HOTPLUG_CPU builds
rcu: Add CPU-offline processing for single-node configurations
rcu: Add "notrace" to RCU function headers used by ftrace
rcu: Remove CONFIG_PREEMPT_RCU
rcu: Merge preemptable-RCU functionality into hierarchical RCU
rcu: Simplify rcu_pending()/rcu_check_callbacks() API
rcu: Use debugfs_remove_recursive() simplify code.
rcu: Merge per-RCU-flavor initialization into pre-existing macro
rcu: Fix online/offline indication for rcudata.csv trace file
rcu: Consolidate sparse and lockdep declarations in include/linux/rcupdate.h
rcu: Renamings to increase RCU clarity
rcu: Move private definitions from include/linux/rcutree.h to kernel/rcutree.h
rcu: Expunge lingering references to CONFIG_CLASSIC_RCU, optimize on !SMP
rcu: Delay rcu_barrier() wait until beginning of next CPU-hotunplug operation.
rcu: Fix typo in rcu_irq_exit() comment header
rcu: Make rcupreempt_trace.c look at offline CPUs
...
Diffstat (limited to 'kernel/rcutree_plugin.h')
-rw-r--r-- | kernel/rcutree_plugin.h | 532 |
1 files changed, 532 insertions, 0 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h new file mode 100644 index 00000000000..47789369ea5 --- /dev/null +++ b/kernel/rcutree_plugin.h @@ -0,0 +1,532 @@ +/* + * Read-Copy Update mechanism for mutual exclusion (tree-based version) + * Internal non-public definitions that provide either classic + * or preemptable semantics. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + * + * Copyright Red Hat, 2009 + * Copyright IBM Corporation, 2009 + * + * Author: Ingo Molnar <mingo@elte.hu> + * Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + + +#ifdef CONFIG_TREE_PREEMPT_RCU + +struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt_state); +DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data); + +/* + * Tell them what RCU they are running. + */ +static inline void rcu_bootup_announce(void) +{ + printk(KERN_INFO + "Experimental preemptable hierarchical RCU implementation.\n"); +} + +/* + * Return the number of RCU-preempt batches processed thus far + * for debug and statistics. + */ +long rcu_batches_completed_preempt(void) +{ + return rcu_preempt_state.completed; +} +EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt); + +/* + * Return the number of RCU batches processed thus far for debug & stats. + */ +long rcu_batches_completed(void) +{ + return rcu_batches_completed_preempt(); +} +EXPORT_SYMBOL_GPL(rcu_batches_completed); + +/* + * Record a preemptable-RCU quiescent state for the specified CPU. Note + * that this just means that the task currently running on the CPU is + * 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) +{ + struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); + rdp->passed_quiesc = 1; + rdp->passed_quiesc_completed = rdp->completed; +} + +/* + * 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. + */ +static void rcu_preempt_qs(int cpu) +{ + struct task_struct *t = current; + int phase; + struct rcu_data *rdp; + struct rcu_node *rnp; + + if (t->rcu_read_lock_nesting && + (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { + + /* Possibly blocking in an RCU read-side critical section. */ + rdp = rcu_preempt_state.rda[cpu]; + rnp = rdp->mynode; + spin_lock(&rnp->lock); + t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; + t->rcu_blocked_node = rnp; + + /* + * If this CPU has already checked in, then this task + * will hold up the next grace period rather than the + * current grace period. Queue the task accordingly. + * If the task is queued for the current grace period + * (i.e., this CPU has not yet passed through a quiescent + * state for the current grace period), then as long + * as that task remains queued, the current grace period + * cannot end. + */ + phase = !(rnp->qsmask & rdp->grpmask) ^ (rnp->gpnum & 0x1); + list_add(&t->rcu_node_entry, &rnp->blocked_tasks[phase]); + smp_mb(); /* Ensure later ctxt swtch seen after above. */ + spin_unlock(&rnp->lock); + } + + /* + * Either we were not in an RCU read-side critical section to + * begin with, or we have now recorded that critical section + * globally. Either way, we can now note a quiescent state + * for this CPU. Again, if we were in an RCU read-side critical + * section, and if that critical section was blocking the current + * 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); +} + +/* + * Tree-preemptable RCU implementation for rcu_read_lock(). + * Just increment ->rcu_read_lock_nesting, shared state will be updated + * if we block. + */ +void __rcu_read_lock(void) +{ + ACCESS_ONCE(current->rcu_read_lock_nesting)++; + barrier(); /* needed if we ever invoke rcu_read_lock in rcutree.c */ +} +EXPORT_SYMBOL_GPL(__rcu_read_lock); + +static void rcu_read_unlock_special(struct task_struct *t) +{ + int empty; + unsigned long flags; + unsigned long mask; + struct rcu_node *rnp; + int special; + + /* NMI handlers cannot block and cannot safely manipulate state. */ + if (in_nmi()) + return; + + local_irq_save(flags); + + /* + * If RCU core is waiting for this CPU to exit critical section, + * let it know that we have done so. + */ + 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; + } + + /* Hardware IRQ handlers cannot block. */ + if (in_irq()) { + local_irq_restore(flags); + return; + } + + /* Clean up if blocked during RCU read-side critical section. */ + if (special & RCU_READ_UNLOCK_BLOCKED) { + t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; + + /* + * Remove this task from the list it blocked on. The + * task can migrate while we acquire the lock, but at + * most one time. So at most two passes through loop. + */ + for (;;) { + rnp = t->rcu_blocked_node; + spin_lock(&rnp->lock); + if (rnp == t->rcu_blocked_node) + break; + spin_unlock(&rnp->lock); + } + empty = list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]); + list_del_init(&t->rcu_node_entry); + t->rcu_blocked_node = NULL; + + /* + * 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. + */ + 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); + 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; + spin_unlock_irqrestore(&rnp->lock, flags); + rnp = rnp->parent; + spin_lock_irqsave(&rnp->lock, flags); + cpu_quiet_msk(mask, &rcu_preempt_state, rnp, flags); + return; + } + spin_unlock(&rnp->lock); + } + local_irq_restore(flags); +} + +/* + * Tree-preemptable RCU implementation for rcu_read_unlock(). + * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost + * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then + * invoke rcu_read_unlock_special() to clean up after a context switch + * in an RCU read-side critical section and other special cases. + */ +void __rcu_read_unlock(void) +{ + struct task_struct *t = current; + + barrier(); /* needed if we ever invoke rcu_read_unlock in rcutree.c */ + if (--ACCESS_ONCE(t->rcu_read_lock_nesting) == 0 && + unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) + rcu_read_unlock_special(t); +} +EXPORT_SYMBOL_GPL(__rcu_read_unlock); + +#ifdef CONFIG_RCU_CPU_STALL_DETECTOR + +/* + * Scan the current list of tasks blocked within RCU read-side critical + * sections, printing out the tid of each. + */ +static void rcu_print_task_stall(struct rcu_node *rnp) +{ + unsigned long flags; + struct list_head *lp; + int phase = rnp->gpnum & 0x1; + struct task_struct *t; + + if (!list_empty(&rnp->blocked_tasks[phase])) { + spin_lock_irqsave(&rnp->lock, flags); + phase = rnp->gpnum & 0x1; /* re-read under lock. */ + lp = &rnp->blocked_tasks[phase]; + list_for_each_entry(t, lp, rcu_node_entry) + printk(" P%d", t->pid); + spin_unlock_irqrestore(&rnp->lock, flags); + } +} + +#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. + */ +static int rcu_preempted_readers(struct rcu_node *rnp) +{ + return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]); +} + +#ifdef CONFIG_HOTPLUG_CPU + +/* + * Handle tasklist migration for case in which all CPUs covered by the + * specified rcu_node have gone offline. Move them up to the root + * 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. + * + * The caller must hold rnp->lock with irqs disabled. + */ +static void rcu_preempt_offline_tasks(struct rcu_state *rsp, + struct rcu_node *rnp) +{ + int i; + struct list_head *lp; + struct list_head *lp_root; + struct rcu_node *rnp_root = rcu_get_root(rsp); + struct task_struct *tp; + + if (rnp == rnp_root) { + WARN_ONCE(1, "Last CPU thought to be offlined?"); + return; /* Shouldn't happen: at least one CPU online. */ + } + + /* + * Move tasks up to root rcu_node. Rely on the fact that the + * root rcu_node can be at most one ahead of the rest of the + * rcu_nodes in terms of gp_num value. This fact allows us to + * move the blocked_tasks[] array directly, element by element. + */ + for (i = 0; i < 2; i++) { + lp = &rnp->blocked_tasks[i]; + lp_root = &rnp_root->blocked_tasks[i]; + while (!list_empty(lp)) { + tp = list_entry(lp->next, typeof(*tp), rcu_node_entry); + spin_lock(&rnp_root->lock); /* irqs already disabled */ + list_del(&tp->rcu_node_entry); + tp->rcu_blocked_node = rnp_root; + list_add(&tp->rcu_node_entry, lp_root); + spin_unlock(&rnp_root->lock); /* irqs remain disabled */ + } + } +} + +/* + * Do CPU-offline processing for preemptable RCU. + */ +static void rcu_preempt_offline_cpu(int cpu) +{ + __rcu_offline_cpu(cpu, &rcu_preempt_state); +} + +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ + +/* + * Check for a quiescent state from the current CPU. When a task blocks, + * the task is recorded in the corresponding CPU's rcu_node structure, + * which is checked elsewhere. + * + * Caller must disable hard irqs. + */ +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); + 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; + } + } +} + +/* + * Process callbacks for preemptable RCU. + */ +static void rcu_preempt_process_callbacks(void) +{ + __rcu_process_callbacks(&rcu_preempt_state, + &__get_cpu_var(rcu_preempt_data)); +} + +/* + * Queue a preemptable-RCU callback for invocation after a grace period. + */ +void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, &rcu_preempt_state); +} +EXPORT_SYMBOL_GPL(call_rcu); + +/* + * Check to see if there is any immediate preemptable-RCU-related work + * to be done. + */ +static int rcu_preempt_pending(int cpu) +{ + return __rcu_pending(&rcu_preempt_state, + &per_cpu(rcu_preempt_data, cpu)); +} + +/* + * Does preemptable RCU need the CPU to stay out of dynticks mode? + */ +static int rcu_preempt_needs_cpu(int cpu) +{ + return !!per_cpu(rcu_preempt_data, cpu).nxtlist; +} + +/* + * Initialize preemptable RCU's per-CPU data. + */ +static void __cpuinit rcu_preempt_init_percpu_data(int cpu) +{ + rcu_init_percpu_data(cpu, &rcu_preempt_state, 1); +} + +/* + * 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 + * 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 */ + +/* + * Tell them what RCU they are running. + */ +static inline void rcu_bootup_announce(void) +{ + printk(KERN_INFO "Hierarchical RCU implementation.\n"); +} + +/* + * Return the number of RCU batches processed thus far for debug & stats. + */ +long rcu_batches_completed(void) +{ + return rcu_batches_completed_sched(); +} +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) +{ +} + +#ifdef CONFIG_RCU_CPU_STALL_DETECTOR + +/* + * Because preemptable RCU does not exist, we never have to check for + * tasks blocked within RCU read-side critical sections. + */ +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. + */ +static int rcu_preempted_readers(struct rcu_node *rnp) +{ + return 0; +} + +#ifdef CONFIG_HOTPLUG_CPU + +/* + * Because preemptable RCU does not exist, it never needs to migrate + * tasks that were blocked within RCU read-side critical sections. + */ +static void rcu_preempt_offline_tasks(struct rcu_state *rsp, + struct rcu_node *rnp) +{ +} + +/* + * Because preemptable RCU does not exist, it never needs CPU-offline + * processing. + */ +static void rcu_preempt_offline_cpu(int cpu) +{ +} + +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ + +/* + * Because preemptable RCU does not exist, it never has any callbacks + * to check. + */ +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) +{ +} + +/* + * In classic RCU, call_rcu() is just call_rcu_sched(). + */ +void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + call_rcu_sched(head, func); +} +EXPORT_SYMBOL_GPL(call_rcu); + +/* + * Because preemptable RCU does not exist, it never has any work to do. + */ +static int rcu_preempt_pending(int cpu) +{ + return 0; +} + +/* + * Because preemptable RCU does not exist, it never needs any CPU. + */ +static int rcu_preempt_needs_cpu(int cpu) +{ + return 0; +} + +/* + * Because preemptable RCU does not exist, there is no per-CPU + * data to initialize. + */ +static void __cpuinit rcu_preempt_init_percpu_data(int cpu) +{ +} + +#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ |