*
* Authors: Dipankar Sarma <dipankar@in.ibm.com>
* Manfred Spraul <manfred@colorfullife.com>
- *
+ *
* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
* Papers:
* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
*
* For detailed explanation of Read-Copy Update mechanism see -
- * http://lse.sourceforge.net/locking/rcupdate.html
+ * http://lse.sourceforge.net/locking/rcupdate.html
*
*/
#include <linux/types.h>
#include <linux/sched.h>
#include <asm/atomic.h>
#include <linux/bitops.h>
-#include <linux/completion.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/module.h>
+#include <linux/kernel_stat.h>
-struct rcu_synchronize {
- struct rcu_head head;
- struct completion completion;
-};
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+static struct lock_class_key rcu_lock_key;
+struct lockdep_map rcu_lock_map =
+ STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
+EXPORT_SYMBOL_GPL(rcu_lock_map);
+#endif
-static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
-static atomic_t rcu_barrier_cpu_count;
-static DEFINE_MUTEX(rcu_barrier_mutex);
-static struct completion rcu_barrier_completion;
+int rcu_scheduler_active __read_mostly;
-/* Because of FASTCALL declaration of complete, we use this wrapper */
-static void wakeme_after_rcu(struct rcu_head *head)
+/*
+ * Awaken the corresponding synchronize_rcu() instance now that a
+ * grace period has elapsed.
+ */
+void wakeme_after_rcu(struct rcu_head *head)
{
struct rcu_synchronize *rcu;
complete(&rcu->completion);
}
+#ifdef CONFIG_TREE_PREEMPT_RCU
+
/**
* synchronize_rcu - wait until a grace period has elapsed.
*
{
struct rcu_synchronize rcu;
+ if (!rcu_scheduler_active)
+ return;
+
init_completion(&rcu.completion);
- /* Will wake me after RCU finished */
+ /* Will wake me after RCU finished. */
call_rcu(&rcu.head, wakeme_after_rcu);
-
- /* Wait for it */
+ /* Wait for it. */
wait_for_completion(&rcu.completion);
}
EXPORT_SYMBOL_GPL(synchronize_rcu);
-static void rcu_barrier_callback(struct rcu_head *notused)
-{
- if (atomic_dec_and_test(&rcu_barrier_cpu_count))
- complete(&rcu_barrier_completion);
-}
+#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
-/*
- * Called with preemption disabled, and from cross-cpu IRQ context.
+/**
+ * synchronize_sched - wait until an rcu-sched grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full rcu-sched
+ * grace period has elapsed, in other words after all currently executing
+ * rcu-sched read-side critical sections have completed. These read-side
+ * critical sections are delimited by rcu_read_lock_sched() and
+ * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
+ * local_irq_disable(), and so on may be used in place of
+ * rcu_read_lock_sched().
+ *
+ * This means that all preempt_disable code sequences, including NMI and
+ * hardware-interrupt handlers, in progress on entry will have completed
+ * before this primitive returns. However, this does not guarantee that
+ * softirq handlers will have completed, since in some kernels, these
+ * handlers can run in process context, and can block.
+ *
+ * This primitive provides the guarantees made by the (now removed)
+ * synchronize_kernel() API. In contrast, synchronize_rcu() only
+ * guarantees that rcu_read_lock() sections will have completed.
+ * In "classic RCU", these two guarantees happen to be one and
+ * the same, but can differ in realtime RCU implementations.
*/
-static void rcu_barrier_func(void *notused)
+void synchronize_sched(void)
{
- int cpu = smp_processor_id();
- struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
+ struct rcu_synchronize rcu;
- atomic_inc(&rcu_barrier_cpu_count);
- call_rcu(head, rcu_barrier_callback);
+ if (rcu_blocking_is_gp())
+ return;
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished. */
+ call_rcu_sched(&rcu.head, wakeme_after_rcu);
+ /* Wait for it. */
+ wait_for_completion(&rcu.completion);
}
+EXPORT_SYMBOL_GPL(synchronize_sched);
/**
- * rcu_barrier - Wait until all the in-flight RCUs are complete.
+ * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full rcu_bh grace
+ * period has elapsed, in other words after all currently executing rcu_bh
+ * read-side critical sections have completed. RCU read-side critical
+ * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
+ * and may be nested.
*/
-void rcu_barrier(void)
+void synchronize_rcu_bh(void)
+{
+ struct rcu_synchronize rcu;
+
+ if (rcu_blocking_is_gp())
+ return;
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished. */
+ call_rcu_bh(&rcu.head, wakeme_after_rcu);
+ /* Wait for it. */
+ wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
+
+static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
+ unsigned long action, void *hcpu)
{
- BUG_ON(in_interrupt());
- /* Take cpucontrol mutex to protect against CPU hotplug */
- mutex_lock(&rcu_barrier_mutex);
- init_completion(&rcu_barrier_completion);
- atomic_set(&rcu_barrier_cpu_count, 0);
- on_each_cpu(rcu_barrier_func, NULL, 0, 1);
- wait_for_completion(&rcu_barrier_completion);
- mutex_unlock(&rcu_barrier_mutex);
+ return rcu_cpu_notify(self, action, hcpu);
}
-EXPORT_SYMBOL_GPL(rcu_barrier);
void __init rcu_init(void)
{
+ int i;
+
__rcu_init();
+ cpu_notifier(rcu_barrier_cpu_hotplug, 0);
+
+ /*
+ * We don't need protection against CPU-hotplug here because
+ * this is called early in boot, before either interrupts
+ * or the scheduler are operational.
+ */
+ for_each_online_cpu(i)
+ rcu_barrier_cpu_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)i);
}
+void rcu_scheduler_starting(void)
+{
+ WARN_ON(num_online_cpus() != 1);
+ WARN_ON(nr_context_switches() > 0);
+ rcu_scheduler_active = 1;
+}
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff