*
* 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/smp.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
-#include <asm/atomic.h>
+#include <linux/atomic.h>
#include <linux/bitops.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>
+#include <linux/hardirq.h>
-enum rcu_barrier {
- RCU_BARRIER_STD,
- RCU_BARRIER_BH,
- RCU_BARRIER_SCHED,
-};
+#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);
+
+static struct lock_class_key rcu_bh_lock_key;
+struct lockdep_map rcu_bh_lock_map =
+ STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
+EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
+
+static struct lock_class_key rcu_sched_lock_key;
+struct lockdep_map rcu_sched_lock_map =
+ STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
+EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
+#endif
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+int debug_lockdep_rcu_enabled(void)
+{
+ return rcu_scheduler_active && debug_locks &&
+ current->lockdep_recursion == 0;
+}
+EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
+
+/**
+ * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
+ *
+ * Check for bottom half being disabled, which covers both the
+ * CONFIG_PROVE_RCU and not cases. Note that if someone uses
+ * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
+ * will show the situation. This is useful for debug checks in functions
+ * that require that they be called within an RCU read-side critical
+ * section.
+ *
+ * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
+ */
+int rcu_read_lock_bh_held(void)
+{
+ if (!debug_lockdep_rcu_enabled())
+ return 1;
+ return in_softirq() || irqs_disabled();
+}
+EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
-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;
+#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
/*
* Awaken the corresponding synchronize_rcu() instance now that a
complete(&rcu->completion);
}
-/**
- * synchronize_rcu - wait until a grace period has elapsed.
- *
- * Control will return to the caller some time after a full grace
- * period has elapsed, in other words after all currently executing RCU
- * read-side critical sections have completed. RCU read-side critical
- * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
- * and may be nested.
+#ifdef CONFIG_PROVE_RCU
+/*
+ * wrapper function to avoid #include problems.
*/
-void synchronize_rcu(void)
+int rcu_my_thread_group_empty(void)
{
- struct rcu_synchronize rcu;
-
- if (rcu_blocking_is_gp())
- return;
-
- init_completion(&rcu.completion);
- /* Will wake me after RCU finished. */
- call_rcu(&rcu.head, wakeme_after_rcu);
- /* Wait for it. */
- wait_for_completion(&rcu.completion);
+ return thread_group_empty(current);
}
-EXPORT_SYMBOL_GPL(synchronize_rcu);
+EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
+#endif /* #ifdef CONFIG_PROVE_RCU */
-static void rcu_barrier_callback(struct rcu_head *notused)
+#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
+static inline void debug_init_rcu_head(struct rcu_head *head)
{
- if (atomic_dec_and_test(&rcu_barrier_cpu_count))
- complete(&rcu_barrier_completion);
+ debug_object_init(head, &rcuhead_debug_descr);
}
-/*
- * Called with preemption disabled, and from cross-cpu IRQ context.
- */
-static void rcu_barrier_func(void *type)
+static inline void debug_rcu_head_free(struct rcu_head *head)
{
- int cpu = smp_processor_id();
- struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
-
- atomic_inc(&rcu_barrier_cpu_count);
- switch ((enum rcu_barrier)type) {
- case RCU_BARRIER_STD:
- call_rcu(head, rcu_barrier_callback);
- break;
- case RCU_BARRIER_BH:
- call_rcu_bh(head, rcu_barrier_callback);
- break;
- case RCU_BARRIER_SCHED:
- call_rcu_sched(head, rcu_barrier_callback);
- break;
- }
+ debug_object_free(head, &rcuhead_debug_descr);
}
-static inline void wait_migrated_callbacks(void);
-
/*
- * Orchestrate the specified type of RCU barrier, waiting for all
- * RCU callbacks of the specified type to complete.
+ * fixup_init is called when:
+ * - an active object is initialized
*/
-static void _rcu_barrier(enum rcu_barrier type)
+static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
{
- BUG_ON(in_interrupt());
- /* Take cpucontrol mutex to protect against CPU hotplug */
- mutex_lock(&rcu_barrier_mutex);
- init_completion(&rcu_barrier_completion);
- /*
- * Initialize rcu_barrier_cpu_count to 1, then invoke
- * rcu_barrier_func() on each CPU, so that each CPU also has
- * incremented rcu_barrier_cpu_count. Only then is it safe to
- * decrement rcu_barrier_cpu_count -- otherwise the first CPU
- * might complete its grace period before all of the other CPUs
- * did their increment, causing this function to return too
- * early.
- */
- atomic_set(&rcu_barrier_cpu_count, 1);
- on_each_cpu(rcu_barrier_func, (void *)type, 1);
- if (atomic_dec_and_test(&rcu_barrier_cpu_count))
- complete(&rcu_barrier_completion);
- wait_for_completion(&rcu_barrier_completion);
- mutex_unlock(&rcu_barrier_mutex);
- wait_migrated_callbacks();
-}
+ struct rcu_head *head = addr;
-/**
- * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
- */
-void rcu_barrier(void)
-{
- _rcu_barrier(RCU_BARRIER_STD);
+ switch (state) {
+ case ODEBUG_STATE_ACTIVE:
+ /*
+ * Ensure that queued callbacks are all executed.
+ * If we detect that we are nested in a RCU read-side critical
+ * section, we should simply fail, otherwise we would deadlock.
+ * In !PREEMPT configurations, there is no way to tell if we are
+ * in a RCU read-side critical section or not, so we never
+ * attempt any fixup and just print a warning.
+ */
+#ifndef CONFIG_PREEMPT
+ WARN_ON_ONCE(1);
+ return 0;
+#endif
+ if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
+ irqs_disabled()) {
+ WARN_ON_ONCE(1);
+ return 0;
+ }
+ rcu_barrier();
+ rcu_barrier_sched();
+ rcu_barrier_bh();
+ debug_object_init(head, &rcuhead_debug_descr);
+ return 1;
+ default:
+ return 0;
+ }
}
-EXPORT_SYMBOL_GPL(rcu_barrier);
-/**
- * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
+/*
+ * fixup_activate is called when:
+ * - an active object is activated
+ * - an unknown object is activated (might be a statically initialized object)
+ * Activation is performed internally by call_rcu().
*/
-void rcu_barrier_bh(void)
+static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
{
- _rcu_barrier(RCU_BARRIER_BH);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_bh);
+ struct rcu_head *head = addr;
-/**
- * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
- */
-void rcu_barrier_sched(void)
-{
- _rcu_barrier(RCU_BARRIER_SCHED);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+ switch (state) {
-static atomic_t rcu_migrate_type_count = ATOMIC_INIT(0);
-static struct rcu_head rcu_migrate_head[3];
-static DECLARE_WAIT_QUEUE_HEAD(rcu_migrate_wq);
+ case ODEBUG_STATE_NOTAVAILABLE:
+ /*
+ * This is not really a fixup. We just make sure that it is
+ * tracked in the object tracker.
+ */
+ debug_object_init(head, &rcuhead_debug_descr);
+ debug_object_activate(head, &rcuhead_debug_descr);
+ return 0;
-static void rcu_migrate_callback(struct rcu_head *notused)
-{
- if (atomic_dec_and_test(&rcu_migrate_type_count))
- wake_up(&rcu_migrate_wq);
+ case ODEBUG_STATE_ACTIVE:
+ /*
+ * Ensure that queued callbacks are all executed.
+ * If we detect that we are nested in a RCU read-side critical
+ * section, we should simply fail, otherwise we would deadlock.
+ * In !PREEMPT configurations, there is no way to tell if we are
+ * in a RCU read-side critical section or not, so we never
+ * attempt any fixup and just print a warning.
+ */
+#ifndef CONFIG_PREEMPT
+ WARN_ON_ONCE(1);
+ return 0;
+#endif
+ if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
+ irqs_disabled()) {
+ WARN_ON_ONCE(1);
+ return 0;
+ }
+ rcu_barrier();
+ rcu_barrier_sched();
+ rcu_barrier_bh();
+ debug_object_activate(head, &rcuhead_debug_descr);
+ return 1;
+ default:
+ return 0;
+ }
}
-static inline void wait_migrated_callbacks(void)
+/*
+ * fixup_free is called when:
+ * - an active object is freed
+ */
+static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
{
- wait_event(rcu_migrate_wq, !atomic_read(&rcu_migrate_type_count));
-}
+ struct rcu_head *head = addr;
-static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
- unsigned long action, void *hcpu)
-{
- if (action == CPU_DYING) {
+ switch (state) {
+ case ODEBUG_STATE_ACTIVE:
/*
- * preempt_disable() in on_each_cpu() prevents stop_machine(),
- * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);"
- * returns, all online cpus have queued rcu_barrier_func(),
- * and the dead cpu(if it exist) queues rcu_migrate_callback()s.
- *
- * These callbacks ensure _rcu_barrier() waits for all
- * RCU callbacks of the specified type to complete.
+ * Ensure that queued callbacks are all executed.
+ * If we detect that we are nested in a RCU read-side critical
+ * section, we should simply fail, otherwise we would deadlock.
+ * In !PREEMPT configurations, there is no way to tell if we are
+ * in a RCU read-side critical section or not, so we never
+ * attempt any fixup and just print a warning.
*/
- atomic_set(&rcu_migrate_type_count, 3);
- call_rcu_bh(rcu_migrate_head, rcu_migrate_callback);
- call_rcu_sched(rcu_migrate_head + 1, rcu_migrate_callback);
- call_rcu(rcu_migrate_head + 2, rcu_migrate_callback);
- } else if (action == CPU_POST_DEAD) {
- /* rcu_migrate_head is protected by cpu_add_remove_lock */
- wait_migrated_callbacks();
+#ifndef CONFIG_PREEMPT
+ WARN_ON_ONCE(1);
+ return 0;
+#endif
+ if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
+ irqs_disabled()) {
+ WARN_ON_ONCE(1);
+ return 0;
+ }
+ rcu_barrier();
+ rcu_barrier_sched();
+ rcu_barrier_bh();
+ debug_object_free(head, &rcuhead_debug_descr);
+ return 1;
+ default:
+ return 0;
}
-
- return NOTIFY_OK;
}
-void __init rcu_init(void)
+/**
+ * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
+ * @head: pointer to rcu_head structure to be initialized
+ *
+ * This function informs debugobjects of a new rcu_head structure that
+ * has been allocated as an auto variable on the stack. This function
+ * is not required for rcu_head structures that are statically defined or
+ * that are dynamically allocated on the heap. This function has no
+ * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
+ */
+void init_rcu_head_on_stack(struct rcu_head *head)
{
- __rcu_init();
- hotcpu_notifier(rcu_barrier_cpu_hotplug, 0);
+ debug_object_init_on_stack(head, &rcuhead_debug_descr);
}
+EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
-void rcu_scheduler_starting(void)
+/**
+ * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
+ * @head: pointer to rcu_head structure to be initialized
+ *
+ * This function informs debugobjects that an on-stack rcu_head structure
+ * is about to go out of scope. As with init_rcu_head_on_stack(), this
+ * function is not required for rcu_head structures that are statically
+ * defined or that are dynamically allocated on the heap. Also as with
+ * init_rcu_head_on_stack(), this function has no effect for
+ * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
+ */
+void destroy_rcu_head_on_stack(struct rcu_head *head)
{
- WARN_ON(num_online_cpus() != 1);
- WARN_ON(nr_context_switches() > 0);
- rcu_scheduler_active = 1;
+ debug_object_free(head, &rcuhead_debug_descr);
}
+EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
+
+struct debug_obj_descr rcuhead_debug_descr = {
+ .name = "rcu_head",
+ .fixup_init = rcuhead_fixup_init,
+ .fixup_activate = rcuhead_fixup_activate,
+ .fixup_free = rcuhead_fixup_free,
+};
+EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
+#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
Code Review / linux-2.6.git / blobdiff