SenseApiLib:Add isBeingDestroyed atomic flag for getter bailout

Since we have no choice but to access the sh_ptr<SenseApiLib> for
a lib before we can get its Qutex, we use this flag to ensure that
we can know whether the SenseApiLib data structure and its Qutex
are still valid when we enter -- i.e, we ensure that the SenseApiLib
object wasn't destroyed under our feet.

smocore/deviceManager/deviceManager.cpp

@@ -324,10 +324,11 @@ public:
 		const std::shared_ptr<DeviceAttachmentSpec>& spec,
 		const std::shared_ptr<ComponentThread> &caller,
 		Callback<attachSenseDeviceReqCbFn> cb,
+		std::shared_ptr<sense_api::SenseApiLib> &senseApiLib,
 		std::vector<std::reference_wrapper<Qutex>> requiredLocks)
 	:	SerializedAsynchronousContinuation<attachSenseDeviceReqCbFn>(
 			caller, cb, requiredLocks),
-		spec(spec)
+		spec(spec), senseApiLib(senseApiLib)
 	{}
 
 public:
@@ -344,26 +345,18 @@ public:
 			return;
 		}
 
-		/**		FIXME:
-		 * We should acquire a spinlock here to ensure that the device isn't
-		 * added in the interim while the async op executes.
-		 */
-		auto libOpt = sense_api::SenseApiManager::getInstance()
-			.getSenseApiLibByApiName(spec->api);
-
-		if (!libOpt)
+		if (senseApiLib->isBeingDestroyed.load())
 		{
-			std::cerr << std::string(__func__) + ": No library found for API '"
-				<< spec->api << "'" << std::endl;
+			std::cerr << std::string(__func__) + ": Library is being destroyed"
+				<< " for API '" << spec->api << "'. Bailing out." << std::endl;
 			callOriginalCb(false, spec);
 			return;
 		}
 
-		auto& lib = *libOpt.value();
-		if (!lib.senseApiDesc.sal_mgmt_libOps.attachDeviceReq)
+		if (!senseApiLib->senseApiDesc.sal_mgmt_libOps.attachDeviceReq)
 		{
 			std::cerr << std::string(__func__) + ": attachDeviceReq() is NULL "
-				"for library '" << lib.libraryPath << "'" << std::endl;
+				"for library '" << senseApiLib->libraryPath << "'" << std::endl;
 			callOriginalCb(false, spec);
 			return;
 		}
@@ -391,7 +384,7 @@ public:
 				<< spec->deviceIdentifier << " to body thread" << "\n";
 		}
 
-		lib.senseApiDesc.sal_mgmt_libOps.attachDeviceReq(
+		senseApiLib->senseApiDesc.sal_mgmt_libOps.attachDeviceReq(
 			spec, threadForAttachment,
 			{context, std::bind(
 				&AttachSenseDeviceReq::attachSenseDeviceReq2,
@@ -421,32 +414,25 @@ public:
 			return;
 		}
 
-		/**		FIXME:
-		 * We should acquire a spinlock here to ensure that the device isn't
-		 * removed in the interim while the async op executes.
-		 */
-		auto libOpt = sense_api::SenseApiManager::getInstance()
-			.getSenseApiLibByApiName(spec->api);
-
-		if (!libOpt)
+		if (senseApiLib->isBeingDestroyed.load())
 		{
-			std::cerr << std::string(__func__) + ": No library found for API '"
-				<< spec->api << "'" << std::endl;
+			std::cerr << std::string(__func__) + ": Library is being destroyed"
+				<< " for API '" << spec->api << "'. Bailing out." << std::endl;
 			callOriginalCb(false, spec);
 			return;
 		}
-		auto& lib = *libOpt.value();
-		if (!lib.senseApiDesc.sal_mgmt_libOps.detachDeviceReq)
+
+		if (!senseApiLib->senseApiDesc.sal_mgmt_libOps.detachDeviceReq)
 		{
 			std::cerr << std::string(__func__) + ": detachDeviceReq() is NULL "
-				"for library '" << lib.libraryPath << "'" << std::endl;
+				"for library '" << senseApiLib->libraryPath << "'" << std::endl;
 			callOriginalCb(false, spec);
 			return;
 		}
 
 		sense_api::SenseApiManager::getInstance().qutex.release();
 
-		lib.senseApiDesc.sal_mgmt_libOps.detachDeviceReq(
+		senseApiLib->senseApiDesc.sal_mgmt_libOps.detachDeviceReq(
 			spec,
 			{context, std::bind(
 				&DetachSenseDeviceReq::detachSenseDeviceReq2,
@@ -465,6 +451,7 @@ public:
 
 public:
 	std::shared_ptr<DeviceAttachmentSpec> spec;
+	std::shared_ptr<sense_api::SenseApiLib> senseApiLib;
 };
 
 void DeviceManager::attachSenseDeviceReq(
@@ -489,7 +476,7 @@ void DeviceManager::attachSenseDeviceReq(
 	auto& lib = *libOpt.value();
 
 	auto request = std::make_shared<AttachSenseDeviceReq>(
-		spec, caller, cb,
+		spec, caller, cb, libOpt.value(),
 		LockSet<attachSenseDeviceReqCbFn>::Set{
 			std::ref(sense_api::SenseApiManager::getInstance().qutex),
 			std::ref(lib.qutex)
@@ -524,7 +511,7 @@ void DeviceManager::detachSenseDeviceReq(
 	auto& lib = *libOpt.value();
 
 	auto request = std::make_shared<DetachSenseDeviceReq>(
-		spec, caller, cb,
+		spec, caller, cb, libOpt.value(),
 		LockSet<detachSenseDeviceReqCbFn>::Set{
 			std::ref(sense_api::SenseApiManager::getInstance().qutex),
 			std::ref(lib.qutex)

smocore/include/senseApis/senseApiLib.h

@@ -3,6 +3,7 @@
 
 #include <string>
 #include <memory>
+#include <atomic>
 #include <vector>
 #include <dlfcn.h>
 #include <functional>
@@ -30,7 +31,7 @@ public:
 	SenseApiLib(
 		const std::string& path, void *_dlopen_handle,
 		SMO_GET_SENSE_API_DESC_FN_TYPEDEF *descFn)
-	: libraryPath(path), qutex("SenseApiLib-" + path),
+	: libraryPath(path), qutex("SenseApiLib-" + path), isBeingDestroyed(false),
 	dlopen_handle(_dlopen_handle, DlCloser()),
 	SMO_GET_SENSE_API_DESC_FN_NAME(descFn)
 	{}
@@ -50,6 +51,7 @@ public:
 public:
 	std::string libraryPath;
 	Qutex qutex;
+	std::atomic<bool> isBeingDestroyed;
 	std::unique_ptr<void, DlCloser> dlopen_handle;
 	/* UNIMPLEMENTED: API-specific cmdline options. These affect this specific
 	 * sense api lib's behaviour globally.

smocore/senseApis/senseApiManager.cpp

@@ -228,6 +228,10 @@ std::string SenseApiManager::stringifyLibs() const
 
 void SenseApiManager::initializeSenseApiLib(SenseApiLib& lib)
 {
+	/**	FIXME:
+	 * When we eventually make this method async, this method should acquire
+	 * the SenseApiManager's main CRUD qutex.
+	 */
     if (!lib.senseApiDesc.sal_mgmt_libOps.initializeInd)
     {
         throw std::runtime_error(
@@ -239,6 +243,11 @@ void SenseApiManager::initializeSenseApiLib(SenseApiLib& lib)
 
 void SenseApiManager::finalizeSenseApiLib(SenseApiLib& lib)
 {
+	/**	FIXME:
+	 * When we eventually make this method async, this flag should only be set
+	 * after acquiring the SenseApiManager's main CRUD qutex.
+	 */
+    lib.isBeingDestroyed.store(true);
     if (!lib.senseApiDesc.sal_mgmt_libOps.finalizeInd)
     {
         throw std::runtime_error(