Async: Drop-in SyncCancelerForAsyncWork without execUncancelableSegment*

We're doing this to prep for the coro port

include/user/stimulusProducer.h

@@ -14,6 +14,7 @@
 #include <boost/asio/io_service.hpp>
 #include <boost/asio/deadline_timer.hpp>
 #include <spinscale/spinLock.h>
+#include <spinscale/syncCancelerForAsyncWork.h>
 #include "deviceAttachmentSpec.h"
 
 namespace smo {
@@ -41,8 +42,7 @@ public:
 		boost::asio::io_service& ioService_)
 	: deviceAttachmentSpec(deviceAttachmentSpec),
 	ioService(ioService_),
-	shouldContinue(false), timer(ioService),
-	nDeferrals(0)
+	timer(ioService), nDeferrals(0)
 	{}
 
 	virtual ~StimulusProducer() = default;
@@ -59,7 +59,7 @@ public:
 		std::cout << __func__ << ": Starting stimulus producer for device "
 			<< deviceAttachmentSpec->deviceSelector << std::endl;
 
-		shouldContinue = true;
+		stimulusProducerCanceler.startAcceptingWork();
 		nDeferrals = 0;
 		scheduleNextTimeout();
 	}
@@ -109,8 +109,7 @@ public:
 private:
 	boost::asio::io_service& ioService;
 protected:
-	sscl::SpinLock shouldContinueLock;
-	bool shouldContinue;
+	sscl::SyncCancelerForAsyncWork stimulusProducerCanceler;
 private:
 	boost::asio::deadline_timer timer;
 	size_t nDeferrals;