srcu: Move to state-based grace-period sequencing
The current SRCU grace-period processing might never reach the last
portion of srcu_advance_batches(). This is OK given the current
implementation, as the first portion, up to the try_check_zero()
following the srcu_flip() is sufficient to drive grace periods forward.
However, it has the unfortunate side-effect of making it impossible to
determine when a given grace period has ended, and it will be necessary
to efficiently trace ends of grace periods in order to efficiently handle
per-CPU SRCU callback lists.
This commit therefore adds states to the SRCU grace-period processing,
so that the end of a given SRCU grace period is marked by the transition
to the SRCU_STATE_DONE state.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index a598cf3..f149a68 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -48,7 +48,7 @@ struct srcu_struct {
unsigned long completed;
struct srcu_array __percpu *per_cpu_ref;
spinlock_t queue_lock; /* protect ->batch_queue, ->running */
- bool running;
+ int srcu_state;
/* callbacks just queued */
struct rcu_batch batch_queue;
/* callbacks try to do the first check_zero */
@@ -62,6 +62,12 @@ struct srcu_struct {
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
};
+/* Values for -> state variable. */
+#define SRCU_STATE_IDLE 0
+#define SRCU_STATE_SCAN1 1
+#define SRCU_STATE_SCAN2 2
+#define SRCU_STATE_DONE 3
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
int __init_srcu_struct(struct srcu_struct *sp, const char *name,
@@ -89,7 +95,7 @@ void process_srcu(struct work_struct *work);
.completed = -300, \
.per_cpu_ref = &name##_srcu_array, \
.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
- .running = false, \
+ .srcu_state = SRCU_STATE_IDLE, \
.batch_queue = RCU_BATCH_INIT(name.batch_queue), \
.batch_check0 = RCU_BATCH_INIT(name.batch_check0), \
.batch_check1 = RCU_BATCH_INIT(name.batch_check1), \