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Subject[PATCH tip/core/rcu 18/55] rcu: Update comments to reflect softirqs vs. kthreads
Date
From: Paul E. McKenney <paul.mckenney@linaro.org>

We now have kthreads only for flavors of RCU that support boosting,
so update the now-misleading comments accordingly.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcutree.c | 23 ++++++++++++-----------
kernel/rcutree_plugin.h | 3 ++-
2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index eb6e731..4e24399 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -198,7 +198,7 @@ DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
};
#endif /* #ifdef CONFIG_NO_HZ */

-static int blimit = 10; /* Maximum callbacks per softirq. */
+static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */
static int qhimark = 10000; /* If this many pending, ignore blimit. */
static int qlowmark = 100; /* Once only this many pending, use blimit. */

@@ -1261,7 +1261,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)

local_irq_restore(flags);

- /* Re-raise the RCU softirq if there are callbacks remaining. */
+ /* Re-invoke RCU core processing if there are callbacks remaining. */
if (cpu_has_callbacks_ready_to_invoke(rdp))
invoke_rcu_core();
}
@@ -1269,7 +1269,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
/*
* Check to see if this CPU is in a non-context-switch quiescent state
* (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
- * Also schedule the RCU softirq handler.
+ * Also schedule RCU core processing.
*
* This function must be called with hardirqs disabled. It is normally
* invoked from the scheduling-clock interrupt. If rcu_pending returns
@@ -1448,9 +1448,9 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
#endif /* #else #ifdef CONFIG_SMP */

/*
- * This does the RCU processing work from softirq context for the
- * specified rcu_state and rcu_data structures. This may be called
- * only from the CPU to whom the rdp belongs.
+ * This does the RCU core processing work for the specified rcu_state
+ * and rcu_data structures. This may be called only from the CPU to
+ * whom the rdp belongs.
*/
static void
__rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
@@ -1487,7 +1487,7 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
}

/*
- * Do softirq processing for the current CPU.
+ * Do RCU core processing for the current CPU.
*/
static void rcu_process_callbacks(struct softirq_action *unused)
{
@@ -1503,10 +1503,11 @@ static void rcu_process_callbacks(struct softirq_action *unused)
}

/*
- * Wake up the current CPU's kthread. This replaces raise_softirq()
- * in earlier versions of RCU. Note that because we are running on
- * the current CPU with interrupts disabled, the rcu_cpu_kthread_task
- * cannot disappear out from under us.
+ * Schedule RCU callback invocation. If the specified type of RCU
+ * does not support RCU priority boosting, just do a direct call,
+ * otherwise wake up the per-CPU kernel kthread. Note that because we
+ * are running on the current CPU with interrupts disabled, the
+ * rcu_cpu_kthread_task cannot disappear out from under us.
*/
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
{
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index a90bf3c..ecd48a2 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1478,7 +1478,8 @@ static int rcu_cpu_kthread_should_stop(int cpu)

/*
* Per-CPU kernel thread that invokes RCU callbacks. This replaces the
- * earlier RCU softirq.
+ * RCU softirq used in flavors and configurations of RCU that do not
+ * support RCU priority boosting.
*/
static int rcu_cpu_kthread(void *arg)
{
--
1.7.3.2


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