[SYCL] Fix leak of device handle (#2671)

There is a circular dependency between the device_impl and the
platform_impl, each holding a shared pointer to the other, which
prevents their destruction.  The patch replaces the vector of shared
pointers in the platform_impl with a vector of weak_ptr.

Signed-off-by: Chris Perkins <chris.perkins@intel.com>

Author: cperkinsintel

sycl/source/detail/platform_impl.cpp

@@ -300,9 +300,11 @@ std::shared_ptr<device_impl> platform_impl::getOrMakeDeviceImpl(
   const std::lock_guard<std::mutex> Guard(MDeviceMapMutex);
 
   // If we've already seen this device, return the impl
-  for (const std::shared_ptr<device_impl> &Device : MDeviceCache) {
-    if (Device->getHandleRef() == PiDevice)
-      return Device;
+  for (const std::weak_ptr<device_impl> &DeviceWP : MDeviceCache) {
+    if (std::shared_ptr<device_impl> Device = DeviceWP.lock()) {
+      if (Device->getHandleRef() == PiDevice)
+        return Device;
+    }
   }
 
   // Otherwise make the impl

sycl/source/detail/platform_impl.hpp

@@ -195,7 +195,7 @@ class platform_impl {
   bool MHostPlatform = false;
   RT::PiPlatform MPlatform = 0;
   std::shared_ptr<plugin> MPlugin;
-  std::vector<std::shared_ptr<device_impl>> MDeviceCache;
+  std::vector<std::weak_ptr<device_impl>> MDeviceCache;
   std::mutex MDeviceMapMutex;
 };
 

sycl/test/basic_tests/queue/release.cpp

@@ -19,3 +19,4 @@ int main() {
 //CHECK: ---> piContextRelease(
 //CHECK: ---> piKernelRelease(
 //CHECK: ---> piProgramRelease(
+//CHECK: ---> piDeviceRelease(