646 lines
17 KiB
C
646 lines
17 KiB
C
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/*
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* Read-Copy Update mechanism for mutual exclusion (tree-based version)
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* Internal non-public definitions that provide either classic
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* or preemptable semantics.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright Red Hat, 2009
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* Copyright IBM Corporation, 2009
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*
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* Author: Ingo Molnar <mingo@elte.hu>
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* Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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*/
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#ifdef CONFIG_TREE_PREEMPT_RCU
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struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt_state);
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DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
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/*
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* Tell them what RCU they are running.
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*/
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static void rcu_bootup_announce(void)
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{
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printk(KERN_INFO
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"Experimental preemptable hierarchical RCU implementation.\n");
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}
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/*
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* Return the number of RCU-preempt batches processed thus far
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* for debug and statistics.
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*/
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long rcu_batches_completed_preempt(void)
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{
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return rcu_preempt_state.completed;
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt);
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/*
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* Return the number of RCU batches processed thus far for debug & stats.
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*/
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long rcu_batches_completed(void)
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{
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return rcu_batches_completed_preempt();
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed);
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/*
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* Record a preemptable-RCU quiescent state for the specified CPU. Note
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* that this just means that the task currently running on the CPU is
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* not in a quiescent state. There might be any number of tasks blocked
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* while in an RCU read-side critical section.
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*/
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static void rcu_preempt_qs(int cpu)
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{
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struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu);
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rdp->passed_quiesc_completed = rdp->completed;
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barrier();
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rdp->passed_quiesc = 1;
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}
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/*
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* We have entered the scheduler, and the current task might soon be
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* context-switched away from. If this task is in an RCU read-side
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* critical section, we will no longer be able to rely on the CPU to
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* record that fact, so we enqueue the task on the appropriate entry
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* of the blocked_tasks[] array. The task will dequeue itself when
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* it exits the outermost enclosing RCU read-side critical section.
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* Therefore, the current grace period cannot be permitted to complete
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* until the blocked_tasks[] entry indexed by the low-order bit of
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* rnp->gpnum empties.
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*
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* Caller must disable preemption.
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*/
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static void rcu_preempt_note_context_switch(int cpu)
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{
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struct task_struct *t = current;
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unsigned long flags;
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int phase;
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struct rcu_data *rdp;
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struct rcu_node *rnp;
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if (t->rcu_read_lock_nesting &&
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(t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
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/* Possibly blocking in an RCU read-side critical section. */
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rdp = rcu_preempt_state.rda[cpu];
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rnp = rdp->mynode;
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spin_lock_irqsave(&rnp->lock, flags);
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t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
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t->rcu_blocked_node = rnp;
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/*
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* If this CPU has already checked in, then this task
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* will hold up the next grace period rather than the
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* current grace period. Queue the task accordingly.
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* If the task is queued for the current grace period
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* (i.e., this CPU has not yet passed through a quiescent
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* state for the current grace period), then as long
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* as that task remains queued, the current grace period
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* cannot end.
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*
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* But first, note that the current CPU must still be
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* on line!
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*/
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WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0);
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WARN_ON_ONCE(!list_empty(&t->rcu_node_entry));
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phase = (rnp->gpnum + !(rnp->qsmask & rdp->grpmask)) & 0x1;
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list_add(&t->rcu_node_entry, &rnp->blocked_tasks[phase]);
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spin_unlock_irqrestore(&rnp->lock, flags);
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}
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/*
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* Either we were not in an RCU read-side critical section to
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* begin with, or we have now recorded that critical section
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* globally. Either way, we can now note a quiescent state
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* for this CPU. Again, if we were in an RCU read-side critical
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* section, and if that critical section was blocking the current
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* grace period, then the fact that the task has been enqueued
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* means that we continue to block the current grace period.
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*/
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rcu_preempt_qs(cpu);
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local_irq_save(flags);
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t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
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local_irq_restore(flags);
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}
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/*
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* Tree-preemptable RCU implementation for rcu_read_lock().
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* Just increment ->rcu_read_lock_nesting, shared state will be updated
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* if we block.
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*/
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void __rcu_read_lock(void)
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{
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ACCESS_ONCE(current->rcu_read_lock_nesting)++;
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barrier(); /* needed if we ever invoke rcu_read_lock in rcutree.c */
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}
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EXPORT_SYMBOL_GPL(__rcu_read_lock);
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/*
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* Check for preempted RCU readers blocking the current grace period
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* for the specified rcu_node structure. If the caller needs a reliable
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* answer, it must hold the rcu_node's ->lock.
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*/
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static int rcu_preempted_readers(struct rcu_node *rnp)
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{
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return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]);
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}
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static void rcu_read_unlock_special(struct task_struct *t)
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{
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int empty;
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unsigned long flags;
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unsigned long mask;
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struct rcu_node *rnp;
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int special;
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/* NMI handlers cannot block and cannot safely manipulate state. */
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if (in_nmi())
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return;
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local_irq_save(flags);
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/*
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* If RCU core is waiting for this CPU to exit critical section,
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* let it know that we have done so.
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*/
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special = t->rcu_read_unlock_special;
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if (special & RCU_READ_UNLOCK_NEED_QS) {
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t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
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rcu_preempt_qs(smp_processor_id());
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}
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/* Hardware IRQ handlers cannot block. */
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if (in_irq()) {
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local_irq_restore(flags);
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return;
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}
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/* Clean up if blocked during RCU read-side critical section. */
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if (special & RCU_READ_UNLOCK_BLOCKED) {
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t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED;
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/*
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* Remove this task from the list it blocked on. The
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* task can migrate while we acquire the lock, but at
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* most one time. So at most two passes through loop.
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*/
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for (;;) {
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rnp = t->rcu_blocked_node;
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spin_lock(&rnp->lock); /* irqs already disabled. */
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if (rnp == t->rcu_blocked_node)
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break;
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spin_unlock(&rnp->lock); /* irqs remain disabled. */
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}
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empty = !rcu_preempted_readers(rnp);
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list_del_init(&t->rcu_node_entry);
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t->rcu_blocked_node = NULL;
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/*
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* If this was the last task on the current list, and if
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* we aren't waiting on any CPUs, report the quiescent state.
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* Note that both cpu_quiet_msk_finish() and cpu_quiet_msk()
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* drop rnp->lock and restore irq.
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*/
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if (!empty && rnp->qsmask == 0 &&
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!rcu_preempted_readers(rnp)) {
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struct rcu_node *rnp_p;
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if (rnp->parent == NULL) {
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/* Only one rcu_node in the tree. */
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cpu_quiet_msk_finish(&rcu_preempt_state, flags);
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return;
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}
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/* Report up the rest of the hierarchy. */
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mask = rnp->grpmask;
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spin_unlock_irqrestore(&rnp->lock, flags);
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rnp_p = rnp->parent;
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spin_lock_irqsave(&rnp_p->lock, flags);
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WARN_ON_ONCE(rnp->qsmask);
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cpu_quiet_msk(mask, &rcu_preempt_state, rnp_p, flags);
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return;
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}
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spin_unlock(&rnp->lock);
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}
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local_irq_restore(flags);
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}
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/*
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* Tree-preemptable RCU implementation for rcu_read_unlock().
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* Decrement ->rcu_read_lock_nesting. If the result is zero (outermost
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* rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
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* invoke rcu_read_unlock_special() to clean up after a context switch
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* in an RCU read-side critical section and other special cases.
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*/
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void __rcu_read_unlock(void)
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{
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struct task_struct *t = current;
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barrier(); /* needed if we ever invoke rcu_read_unlock in rcutree.c */
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if (--ACCESS_ONCE(t->rcu_read_lock_nesting) == 0 &&
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unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
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rcu_read_unlock_special(t);
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}
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EXPORT_SYMBOL_GPL(__rcu_read_unlock);
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#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
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/*
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* Scan the current list of tasks blocked within RCU read-side critical
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* sections, printing out the tid of each.
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*/
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static void rcu_print_task_stall(struct rcu_node *rnp)
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{
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unsigned long flags;
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struct list_head *lp;
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int phase;
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struct task_struct *t;
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if (rcu_preempted_readers(rnp)) {
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spin_lock_irqsave(&rnp->lock, flags);
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phase = rnp->gpnum & 0x1;
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lp = &rnp->blocked_tasks[phase];
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list_for_each_entry(t, lp, rcu_node_entry)
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printk(" P%d", t->pid);
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spin_unlock_irqrestore(&rnp->lock, flags);
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}
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}
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#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
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/*
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* Check that the list of blocked tasks for the newly completed grace
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* period is in fact empty. It is a serious bug to complete a grace
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* period that still has RCU readers blocked! This function must be
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* invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock
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* must be held by the caller.
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*/
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static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
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{
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WARN_ON_ONCE(rcu_preempted_readers(rnp));
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WARN_ON_ONCE(rnp->qsmask);
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}
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#ifdef CONFIG_HOTPLUG_CPU
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/*
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* Handle tasklist migration for case in which all CPUs covered by the
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* specified rcu_node have gone offline. Move them up to the root
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* rcu_node. The reason for not just moving them to the immediate
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* parent is to remove the need for rcu_read_unlock_special() to
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* make more than two attempts to acquire the target rcu_node's lock.
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*
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* Returns 1 if there was previously a task blocking the current grace
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* period on the specified rcu_node structure.
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*
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* The caller must hold rnp->lock with irqs disabled.
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*/
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static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
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struct rcu_node *rnp,
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struct rcu_data *rdp)
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{
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int i;
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struct list_head *lp;
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struct list_head *lp_root;
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int retval = rcu_preempted_readers(rnp);
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struct rcu_node *rnp_root = rcu_get_root(rsp);
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struct task_struct *tp;
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if (rnp == rnp_root) {
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WARN_ONCE(1, "Last CPU thought to be offlined?");
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return 0; /* Shouldn't happen: at least one CPU online. */
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}
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WARN_ON_ONCE(rnp != rdp->mynode &&
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(!list_empty(&rnp->blocked_tasks[0]) ||
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!list_empty(&rnp->blocked_tasks[1])));
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/*
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* Move tasks up to root rcu_node. Rely on the fact that the
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* root rcu_node can be at most one ahead of the rest of the
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* rcu_nodes in terms of gp_num value. This fact allows us to
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* move the blocked_tasks[] array directly, element by element.
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*/
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for (i = 0; i < 2; i++) {
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lp = &rnp->blocked_tasks[i];
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lp_root = &rnp_root->blocked_tasks[i];
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while (!list_empty(lp)) {
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tp = list_entry(lp->next, typeof(*tp), rcu_node_entry);
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spin_lock(&rnp_root->lock); /* irqs already disabled */
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list_del(&tp->rcu_node_entry);
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tp->rcu_blocked_node = rnp_root;
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list_add(&tp->rcu_node_entry, lp_root);
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spin_unlock(&rnp_root->lock); /* irqs remain disabled */
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}
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}
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return retval;
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}
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/*
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* 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_preempt_qs(cpu);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
if (per_cpu(rcu_preempt_data, cpu).qs_pending)
|
||
|
|
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);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Wait for an rcu-preempt grace period. We are supposed to expedite the
|
||
|
|
* grace period, but this is the crude slow compatability hack, so just
|
||
|
|
* invoke synchronize_rcu().
|
||
|
|
*/
|
||
|
|
void synchronize_rcu_expedited(void)
|
||
|
|
{
|
||
|
|
synchronize_rcu();
|
||
|
|
}
|
||
|
|
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* 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;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* 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.
|
||
|
|
*/
|
||
|
|
static void __cpuinit rcu_preempt_init_percpu_data(int cpu)
|
||
|
|
{
|
||
|
|
rcu_init_percpu_data(cpu, &rcu_preempt_state, 1);
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* 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
|
||
|
|
* 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 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_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
|
||
|
|
|
||
|
|
/*
|
||
|
|
* 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 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 void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
|
||
|
|
{
|
||
|
|
WARN_ON_ONCE(rnp->qsmask);
|
||
|
|
}
|
||
|
|
|
||
|
|
#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, and
|
||
|
|
* such non-existent tasks cannot possibly have been blocking the current
|
||
|
|
* grace period.
|
||
|
|
*/
|
||
|
|
static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
|
||
|
|
struct rcu_node *rnp,
|
||
|
|
struct rcu_data *rdp)
|
||
|
|
{
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* 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.
|
||
|
|
*/
|
||
|
|
static void rcu_preempt_check_callbacks(int cpu)
|
||
|
|
{
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Because preemptable RCU does not exist, it never has any callbacks
|
||
|
|
* to process.
|
||
|
|
*/
|
||
|
|
static 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);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Wait for an rcu-preempt grace period, but make it happen quickly.
|
||
|
|
* But because preemptable RCU does not exist, map to rcu-sched.
|
||
|
|
*/
|
||
|
|
void synchronize_rcu_expedited(void)
|
||
|
|
{
|
||
|
|
synchronize_sched_expedited();
|
||
|
|
}
|
||
|
|
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* 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, 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.
|
||
|
|
*/
|
||
|
|
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 */
|