[PATCH v8 06/21] tracing/remotes: Use a single per-remote polling work

@@ -26,7 +26,6 @@ enum tri_type {
 struct trace_remote_iterator {
 	struct trace_remote		*remote;
 	struct trace_seq		seq;
-	struct delayed_work		poll_work;
 	unsigned long			lost_events;
 	u64				ts;
 	struct ring_buffer_iter		*rb_iter;

@@ -55,8 +54,10 @@ struct trace_remote {
 	struct rw_semaphore		reader_lock;
 	struct rw_semaphore		*pcpu_reader_locks;
 	unsigned int			nr_readers;
+	unsigned int			poll_cnt;
 	unsigned int			poll_ms;
 	bool				tracing_on;
+	struct delayed_work		poll_work;
 };
 
 static DEFINE_MUTEX(trace_remotes_lock);

@@ -351,17 +352,6 @@ static bool trace_remote_has_cpu(struct trace_remote *remote, int cpu)
 	return ring_buffer_poll_remote(remote->trace_buffer, cpu) == 0;
 }
 
-static void __poll_remote(struct work_struct *work)
-{
-	struct delayed_work *dwork = to_delayed_work(work);
-	struct trace_remote_iterator *iter;
-
-	iter = container_of(dwork, struct trace_remote_iterator, poll_work);
-	ring_buffer_poll_remote(iter->remote->trace_buffer, iter->cpu);
-	schedule_delayed_work((struct delayed_work *)work,
-			      msecs_to_jiffies(iter->remote->poll_ms));
-}
-
 static void __free_ring_buffer_iter(struct trace_remote_iterator *iter, int cpu)
 {
 	if (cpu != RING_BUFFER_ALL_CPUS) {

@@ -405,6 +395,36 @@ static int __alloc_ring_buffer_iter(struct trace_remote_iterator *iter, int cpu)
 	return 0;
 }
 
+static void trace_remote_do_poll(struct trace_remote *remote)
+{
+	ring_buffer_poll_remote(remote->trace_buffer, RING_BUFFER_ALL_CPUS);
+	schedule_delayed_work(&remote->poll_work, msecs_to_jiffies(remote->poll_ms));
+}
+
+static void __poll_remote(struct work_struct *work)
+{
+	struct delayed_work *dwork = to_delayed_work(work);
+
+	trace_remote_do_poll(container_of(dwork, struct trace_remote, poll_work));
+}
+
+static void trace_remote_inc_poll(struct trace_remote *remote)
+{
+	/* poll_cnt <= nr_readers, inherits its overflow protection */
+	if (!remote->poll_cnt++)
+		trace_remote_do_poll(remote);
+}
+
+static void trace_remote_dec_poll(struct trace_remote *remote)
+{
+	if (WARN_ON_ONCE(!remote->poll_cnt))
+		return;
+
+	remote->poll_cnt--;
+	if (!remote->poll_cnt)
+		cancel_delayed_work_sync(&remote->poll_work);
+}
+
 static struct trace_remote_iterator
 *trace_remote_iter(struct trace_remote *remote, int cpu, enum tri_type type)
 {

@@ -434,9 +454,7 @@ static struct trace_remote_iterator
 
 		switch (type) {
 		case TRI_CONSUMING:
-			ring_buffer_poll_remote(remote->trace_buffer, cpu);
-			INIT_DELAYED_WORK(&iter->poll_work, __poll_remote);
-			schedule_delayed_work(&iter->poll_work, msecs_to_jiffies(remote->poll_ms));
+			trace_remote_inc_poll(remote);
 			break;
 		case TRI_NONCONSUMING:
 			ret = __alloc_ring_buffer_iter(iter, cpu);

@@ -470,7 +488,7 @@ static void trace_remote_iter_free(struct trace_remote_iterator *iter)
 
 	switch (iter->type) {
 	case TRI_CONSUMING:
-		cancel_delayed_work_sync(&iter->poll_work);
+		trace_remote_dec_poll(remote);
 		break;
 	case TRI_NONCONSUMING:
 		__free_ring_buffer_iter(iter, iter->cpu);

@@ -1003,6 +1021,7 @@ int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs,
 	remote->poll_ms = 100;
 	mutex_init(&remote->lock);
 	init_rwsem(&remote->reader_lock);
+	INIT_DELAYED_WORK(&remote->poll_work, __poll_remote);
 
 	guard(mutex)(&trace_remotes_lock);