refactor(userspace/falco): make signal handlers thread-safe

Signed-off-by: Jason Dellaluce <jasondellaluce@gmail.com>

userspace/falco/app_actions/process_events.cpp

@@ -90,13 +90,8 @@ application::run_result application::do_inspect(syscall_evt_drop_mgr &sdropmgr,
 
 		writer.handle();
 
-		if(m_state->reopen_outputs)
-		{
-			m_state->outputs->reopen_outputs();
-			m_state->reopen_outputs = false;
-		}
-
-		if(m_state->terminate || m_state->restart)
+		if(m_state->terminate.load(std::memory_order_acquire)
+			|| m_state->restart.load(std::memory_order_acquire))
 		{
 			break;
 		}

userspace/falco/application.cpp

@@ -41,7 +41,6 @@ application::run_result::~run_result()
 application::state::state()
 	: restart(false),
 	  terminate(false),
-	  reopen_outputs(false),
 	  enabled_sources({falco_common::syscall_source})
 {
 	config = std::make_shared<falco_configuration>();
@@ -67,23 +66,25 @@ void application::terminate()
 {
 	if(m_state != nullptr)
 	{
-		m_state->terminate = true;
+		m_state->terminate.store(true, std::memory_order_release);
 	}
 }
 
 void application::reopen_outputs()
 {
-	if(m_state != nullptr)
+	if(m_state != nullptr && m_state->outputs != nullptr)
 	{
-		m_state->reopen_outputs = true;
+		// note: it is ok to do this inside the signal handler because
+		// in the current falco_outputs implementation this is non-blocking
+		m_state->outputs->reopen_outputs();
 	}
 }
 
 void application::restart()
 {
 	if(m_state != nullptr)
 	{
-		m_state->restart = true;
+		m_state->restart.store(true, std::memory_order_release);
 	}
 }
 

userspace/falco/application.h

@@ -25,6 +25,7 @@ limitations under the License.
 #include "app_cmdline_options.h"
 
 #include <string>
+#include <atomic>
 
 namespace falco {
 namespace app {
@@ -61,9 +62,8 @@ class application {
 		state();
 		virtual ~state();
 
-		bool restart;
-		bool terminate;
-		bool reopen_outputs;
+		std::atomic<bool> restart;
+		std::atomic<bool> terminate;
 
 		std::shared_ptr<falco_configuration> config;
 		std::shared_ptr<falco_outputs> outputs;