Merge branch 'rcu-tasks.2014.09.10a' into HEAD

rcu-tasks.2014.09.10a: Add RCU-tasks flavor of RCU.

1 files changed, 55 insertions, 2 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 334ff89aada0..5cafd60c1ee4 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -55,6 +55,7 @@ enum rcutorture_type {
         RCU_FLAVOR,
         RCU_BH_FLAVOR,
         RCU_SCHED_FLAVOR,
+        RCU_TASKS_FLAVOR,
         SRCU_FLAVOR,
         INVALID_RCU_FLAVOR
 };
@@ -197,6 +198,28 @@ void call_rcu_sched(struct rcu_head *head,
 
 void synchronize_sched(void);
 
+/**
+ * call_rcu_tasks() - Queue an RCU for invocation task-based grace period
+ * @head: structure to be used for queueing the RCU updates.
+ * @func: actual callback function to be invoked after the grace period
+ *
+ * The callback function will be invoked some time after a full grace
+ * period elapses, in other words after all currently executing RCU
+ * read-side critical sections have completed. call_rcu_tasks() assumes
+ * that the read-side critical sections end at a voluntary context
+ * switch (not a preemption!), entry into idle, or transition to usermode
+ * execution.  As such, there are no read-side primitives analogous to
+ * rcu_read_lock() and rcu_read_unlock() because this primitive is intended
+ * to determine that all tasks have passed through a safe state, not so
+ * much for data-strcuture synchronization.
+ *
+ * See the description of call_rcu() for more detailed information on
+ * memory ordering guarantees.
+ */
+void call_rcu_tasks(struct rcu_head *head, void (*func)(struct rcu_head *head));
+void synchronize_rcu_tasks(void);
+void rcu_barrier_tasks(void);
+
 #ifdef CONFIG_PREEMPT_RCU
 
 void __rcu_read_lock(void);
@@ -238,8 +261,8 @@ static inline int rcu_preempt_depth(void)
 
 /* Internal to kernel */
 void rcu_init(void);
-void rcu_sched_qs(int cpu);
-void rcu_bh_qs(int cpu);
+void rcu_sched_qs(void);
+void rcu_bh_qs(void);
 void rcu_check_callbacks(int cpu, int user);
 struct notifier_block;
 void rcu_idle_enter(void);
@@ -302,6 +325,36 @@ static inline void rcu_init_nohz(void)
                 rcu_irq_exit(); \
         } while (0)
 
+/*
+ * Note a voluntary context switch for RCU-tasks benefit.  This is a
+ * macro rather than an inline function to avoid #include hell.
+ */
+#ifdef CONFIG_TASKS_RCU
+#define TASKS_RCU(x) x
+extern struct srcu_struct tasks_rcu_exit_srcu;
+#define rcu_note_voluntary_context_switch(t) \
+        do { \
+                if (ACCESS_ONCE((t)->rcu_tasks_holdout)) \
+                        ACCESS_ONCE((t)->rcu_tasks_holdout) = false; \
+        } while (0)
+#else /* #ifdef CONFIG_TASKS_RCU */
+#define TASKS_RCU(x) do { } while (0)
+#define rcu_note_voluntary_context_switch(t)    do { } while (0)
+#endif /* #else #ifdef CONFIG_TASKS_RCU */
+
+/**
+ * cond_resched_rcu_qs - Report potential quiescent states to RCU
+ *
+ * This macro resembles cond_resched(), except that it is defined to
+ * report potential quiescent states to RCU-tasks even if the cond_resched()
+ * machinery were to be shut off, as some advocate for PREEMPT kernels.
+ */
+#define cond_resched_rcu_qs() \
+do { \
+        rcu_note_voluntary_context_switch(current); \
+        cond_resched(); \
+} while (0)
+
 #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP)
 bool __rcu_is_watching(void);
 #endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */