rcu: Break more call_rcu() deadlock involving scheduler and perf
Commit 96d3fd0d315a9 (rcu: Break call_rcu() deadlock involving scheduler
and perf) covered the case where __call_rcu_nocb_enqueue() needs to wake
the rcuo kthread due to the queue being initially empty, but did not
do anything for the case where the queue was overflowing. This commit
therefore also defers wakeup for the overflow case.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 6a86eb7..e33562f 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -350,7 +350,7 @@
int nocb_p_count_lazy; /* (approximate). */
wait_queue_head_t nocb_wq; /* For nocb kthreads to sleep on. */
struct task_struct *nocb_kthread;
- bool nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
+ int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
/* The following fields are used by the leader, hence own cacheline. */
struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp;
@@ -383,6 +383,11 @@
#define RCU_FORCE_QS 3 /* Need to force quiescent state. */
#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK
+/* Values for nocb_defer_wakeup field in struct rcu_data. */
+#define RCU_NOGP_WAKE_NOT 0
+#define RCU_NOGP_WAKE 1
+#define RCU_NOGP_WAKE_FORCE 2
+
#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
/* For jiffies_till_first_fqs and */
/* and jiffies_till_next_fqs. */
@@ -589,7 +594,7 @@
static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
struct rcu_data *rdp,
unsigned long flags);
-static bool rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
+static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
static void rcu_spawn_nocb_kthreads(struct rcu_state *rsp);