[PATCH v4 tip/core/rcu 31/38] rcu-tasks: Make RCU tasks trace also wait for idle tasks

paulmck
2020-04-15T18:21:54Z

This commit scans the CPUs, adding each CPU's idle task to the list of
tasks that need quiescent states.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tasks.h | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 1888a49..6bd9bfe 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -15,7 +15,7 @@ struct rcu_tasks;
typedef void (*rcu_tasks_gp_func_t)(struct rcu_tasks *rtp);
typedef void (*pregp_func_t)(void);
typedef void (*pertask_func_t)(struct task_struct *t, struct list_head *hop);
-typedef void (*postscan_func_t)(void);
+typedef void (*postscan_func_t)(struct list_head *hop);
typedef void (*holdouts_func_t)(struct list_head *hop, bool ndrpt, bool *frptp);
typedef void (*postgp_func_t)(struct rcu_tasks *rtp);

@@ -331,7 +331,7 @@ static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
rcu_read_unlock();

set_tasks_gp_state(rtp, RTGS_POST_SCAN_TASKLIST);
- rtp->postscan_func();
+ rtp->postscan_func(&holdouts);

/*
* Each pass through the following loop scans the list of holdout
@@ -415,7 +415,7 @@ static void rcu_tasks_pertask(struct task_struct *t, struct list_head *hop)
}

/* Processing between scanning taskslist and draining the holdout list. */
-void rcu_tasks_postscan(void)
+void rcu_tasks_postscan(struct list_head *hop)
{
/*
* Wait for tasks that are in the process of exiting. This
@@ -932,9 +932,17 @@ static void rcu_tasks_trace_pertask(struct task_struct *t,
trc_wait_for_one_reader(t, hop);
}

-/* Do intermediate processing between task and holdout scans. */
-static void rcu_tasks_trace_postscan(void)
+/*
+ * Do intermediate processing between task and holdout scans and
+ * pick up the idle tasks.
+ */
+static void rcu_tasks_trace_postscan(struct list_head *hop)
{
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ rcu_tasks_trace_pertask(idle_task(cpu), hop);
+
// Re-enable CPU hotplug now that the tasklist scan has completed.
cpus_read_unlock();

--
2.9.5