utils: ipc: proxy: Track IPA with a state machine

Asynchronous tasks can only be submitted while the IPA is running.

Further more, the shutdown sequence can not be tracked with a simple
running flag. We can also be in the state 'Stopping' where we have not
yet completed all events, but we must not commence anything new.

Refactor the running_ boolean into a stateful enum to track this.

Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/internal/ipa_proxy.h

@@ -17,6 +17,12 @@ namespace libcamera {
 
 class IPAModule;
 
+enum ProxyState {
+	ProxyStopped,
+	ProxyStopping,
+	ProxyRunning,
+};
+
 class IPAProxy : public IPAInterface
 {
 public:
@@ -31,6 +37,7 @@ protected:
 	std::string resolvePath(const std::string &file) const;
 
 	bool valid_;
+	ProxyState state_;
 
 private:
 	IPAModule *ipam_;

src/libcamera/ipa_proxy.cpp

@@ -37,7 +37,7 @@ LOG_DEFINE_CATEGORY(IPAProxy)
  * \param[in] ipam The IPA module
  */
 IPAProxy::IPAProxy(IPAModule *ipam)
-	: valid_(false), ipam_(ipam)
+	: valid_(false), state_(ProxyStopped), ipam_(ipam)
 {
 }
 

utils/ipc/generators/libcamera_templates/module_ipa_proxy.cpp.tmpl

@@ -45,8 +45,7 @@ namespace {{ns}} {
 {%- endif %}
 
 {{proxy_name}}::{{proxy_name}}(IPAModule *ipam, bool isolate)
-	: IPAProxy(ipam), running_(false),
-	  isolate_(isolate), seq_(0)
+	: IPAProxy(ipam), isolate_(isolate), seq_(0)
 {
 	LOG(IPAProxy, Debug)
 		<< "initializing {{module_name}} proxy: loading IPA from "
@@ -155,7 +154,7 @@ void {{proxy_name}}::recvMessage(const IPCMessage &data)
 
 	return {{ "_ret" if method|method_return_value != "void" }};
 {%- elif method.mojom_name == "start" %}
-	running_ = true;
+	state_ = ProxyRunning;
 	thread_.start();
 
 	{{ "return " if method|method_return_value != "void" -}}
@@ -173,7 +172,7 @@ void {{proxy_name}}::recvMessage(const IPCMessage &data)
 	{%- endfor -%}
 );
 {% elif method|is_async %}
-	ASSERT(running_);
+	ASSERT(state_ == ProxyRunning);
 	proxy_.invokeMethod(&ThreadProxy::{{method.mojom_name}}, ConnectionTypeQueued,
 	{%- for param in method|method_param_names -%}
 		{{param}}{{- ", " if not loop.last}}
@@ -226,7 +225,7 @@ void {{proxy_name}}::recvMessage(const IPCMessage &data)
 {% for method in interface_event.methods %}
 {{proxy_funcs.func_sig(proxy_name, method, "Thread")}}
 {
-	ASSERT(running_);
+	ASSERT(state_ != ProxyStopped);
 	{{method.mojom_name}}.emit({{method.parameters|params_comma_sep}});
 }
 

utils/ipc/generators/libcamera_templates/module_ipa_proxy.h.tmpl

@@ -104,7 +104,6 @@ private:
 		{{interface_name}} *ipa_;
 	};
 
-	bool running_;
 	Thread thread_;
 	ThreadProxy proxy_;
 	std::unique_ptr<{{interface_name}}> ipa_;

utils/ipc/generators/libcamera_templates/proxy_functions.tmpl

@@ -23,9 +23,12 @@
  # \brief Generate function body for IPA stop() function for thread
  #}
 {%- macro stop_thread_body() -%}
-	if (!running_)
+	ASSERT(state_ != ProxyStopping);
+	if (state_ != ProxyRunning)
 		return;
 
+	state_ = ProxyStopping;
+
 	proxy_.invokeMethod(&ThreadProxy::stop, ConnectionTypeBlocking);
 
 	thread_.exit();
@@ -33,7 +36,7 @@
 
 	Thread::current()->dispatchMessages(Message::Type::InvokeMessage);
 
-	running_ = false;
+	state_ = ProxyStopped;
 {%- endmacro -%}