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-rw-r--r--src/libcamera/base/thread.cpp43
1 files changed, 33 insertions, 10 deletions
diff --git a/src/libcamera/base/thread.cpp b/src/libcamera/base/thread.cpp
index 7f791152..1232f895 100644
--- a/src/libcamera/base/thread.cpp
+++ b/src/libcamera/base/thread.cpp
@@ -126,6 +126,11 @@ public:
* \brief Protects the \ref list_
*/
Mutex mutex_;
+ /**
+ * \brief The recursion level for recursive Thread::dispatchMessages()
+ * calls
+ */
+ unsigned int recursion_ = 0;
};
/**
@@ -595,30 +600,34 @@ void Thread::removeMessages(Object *receiver)
* Messages shall only be dispatched from the current thread, typically within
* the thread from the run() function. Calling this function outside of the
* thread results in undefined behaviour.
+ *
+ * This function is not thread-safe, but it may be called recursively in the
+ * same thread from an object's message handler. It guarantees delivery of
+ * messages in the order they have been posted in all cases.
*/
void Thread::dispatchMessages(Message::Type type)
{
ASSERT(data_ == ThreadData::current());
+ ++data_->messages_.recursion_;
+
MutexLocker locker(data_->messages_.mutex_);
std::list<std::unique_ptr<Message>> &messages = data_->messages_.list_;
- for (auto iter = messages.begin(); iter != messages.end(); ) {
- std::unique_ptr<Message> &msg = *iter;
-
- if (!msg) {
- iter = data_->messages_.list_.erase(iter);
+ for (std::unique_ptr<Message> &msg : messages) {
+ if (!msg)
continue;
- }
- if (type != Message::Type::None && msg->type() != type) {
- ++iter;
+ if (type != Message::Type::None && msg->type() != type)
continue;
- }
+ /*
+ * Move the message, setting the entry in the list to null. It
+ * will cause recursive calls to ignore the entry, and the erase
+ * loop at the end of the function to delete it from the list.
+ */
std::unique_ptr<Message> message = std::move(msg);
- iter = data_->messages_.list_.erase(iter);
Object *receiver = message->receiver_;
ASSERT(data_ == receiver->thread()->data_);
@@ -629,6 +638,20 @@ void Thread::dispatchMessages(Message::Type type)
message.reset();
locker.lock();
}
+
+ /*
+ * If the recursion level is 0, erase all null messages in the list. We
+ * can't do so during recursion, as it would invalidate the iterator of
+ * the outer calls.
+ */
+ if (!--data_->messages_.recursion_) {
+ for (auto iter = messages.begin(); iter != messages.end(); ) {
+ if (!*iter)
+ iter = messages.erase(iter);
+ else
+ ++iter;
+ }
+ }
}
/**