[PATCH 1/3] cyclic: make cyclic_unregister() idempotent

[Rasmus Villemoes <ravi@prevas.dk>]

Make cyclic_unregister() safe to call with an already unregistered, or
possibly never registered, struct cyclic_info. This is similar to how
the various timer APIs in the linux kernel work (they all allow
calling delete/cancel/... on an inactive timer object).

This means callers don't have to separately keep track of whether
their cyclic callback is registered or not, and avoids them trying to
peek into the struct cyclic_info for that information - which leads to
somewhat ugly code as it would have to be guarded by ifdef
CONFIG_CYCLIC.

Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>
---
 common/cyclic.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/common/cyclic.c b/common/cyclic.c
index b695f092f52..75662d9f613 100644
--- a/common/cyclic.c
+++ b/common/cyclic.c
@@ -28,6 +28,18 @@ struct hlist_head *cyclic_get_list(void)
 	return (struct hlist_head *)&gd->cyclic_list;
 }
 
+static bool cyclic_is_registered(const struct cyclic_info *cyclic)
+{
+	const struct cyclic_info *c;
+
+	hlist_for_each_entry(c, cyclic_get_list(), list) {
+		if (c == cyclic)
+			return true;
+	}
+
+	return false;
+}
+
 void cyclic_register(struct cyclic_info *cyclic, cyclic_func_t func,
 		     uint64_t delay_us, const char *name)
 {
@@ -43,6 +55,9 @@ void cyclic_register(struct cyclic_info *cyclic, cyclic_func_t func,
 
 void cyclic_unregister(struct cyclic_info *cyclic)
 {
+	if (!cyclic_is_registered(cyclic))
+		return;
+
 	hlist_del(&cyclic->list);
 }
 
-- 
2.49.0