poller: Fix async poller

The async poller does not work as expected since it can happen that
the async poller is removed from the list of pollers while we are
iterating over the list. Even list_for_each_entry_safe does not help
here since we may remove the next list element, but
list_for_each_entry_safe only allows to remove the current list element.

Rework the async poller so that it is registered with the poller
framework on registration and then is only marked as active with
poller_call_async(). This way we do not have to do list manipulations
while running the pollers.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

2 files changed, 26 insertions, 4 deletions

diff --git a/common/poller.c b/common/poller.c
index 496636d1d7..32795b641f 100644
--- a/common/poller.c
+++ b/common/poller.c
@@ -32,6 +32,7 @@ int poller_unregister(struct poller_struct *poller)
 	if (!poller->registered)
 		return -ENODEV;
 
+
 	list_del(&poller->list);
 	poller->registered = 0;
 
@@ -42,12 +43,14 @@ static void poller_async_callback(struct poller_struct *poller)
 {
 	struct poller_async *pa = container_of(poller, struct poller_async, poller);
 
+	if (!pa->active)
+		return;
+
 	if (get_time_ns() < pa->end)
 		return;
 
+	pa->active = 0;
 	pa->fn(pa->ctx);
-	pa->fn = NULL;
-	poller_unregister(&pa->poller);
 }
 
 /*
@@ -62,7 +65,9 @@ static void poller_async_callback(struct poller_struct *poller)
  */
 int poller_async_cancel(struct poller_async *pa)
 {
-	return poller_unregister(&pa->poller);
+	pa->active = 0;
+
+	return 0;
 }
 
 /*
@@ -80,13 +85,26 @@ int poller_call_async(struct poller_async *pa, uint64_t delay_ns,
 		void (*fn)(void *), void *ctx)
 {
 	pa->ctx = ctx;
-	pa->poller.func = poller_async_callback;
 	pa->end = get_time_ns() + delay_ns;
 	pa->fn = fn;
+	pa->active = 1;
+
+	return 0;
+}
+
+int poller_async_register(struct poller_async *pa)
+{
+	pa->poller.func = poller_async_callback;
+	pa->active = 0;
 
 	return poller_register(&pa->poller);
 }
 
+int poller_async_unregister(struct poller_async *pa)
+{
+	return poller_unregister(&pa->poller);
+}
+
 void poller_call(void)
 {
 	struct poller_struct *poller, *tmp;
diff --git a/include/poller.h b/include/poller.h
index cda5b5774b..35a2271d69 100644
--- a/include/poller.h
+++ b/include/poller.h
@@ -26,8 +26,12 @@ struct poller_async {
 	void (*fn)(void *);
 	void *ctx;
 	uint64_t end;
+	int active;
 };
 
+int poller_async_register(struct poller_async *pa);
+int poller_async_unregister(struct poller_async *pa);
+
 int poller_call_async(struct poller_async *pa, uint64_t delay_ns,
 		void (*fn)(void *), void *ctx);
 int poller_async_cancel(struct poller_async *pa);