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[SYCL][UR] Do not call urDeviceRetain() in device_impl constructor at all #20065

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[SYCL][UR] Do not call urDeviceRetain() in device_impl constructor at all #20065

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6 changes: 3 additions & 3 deletions sycl/source/detail/device_impl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -30,9 +30,9 @@ device_impl::device_impl(ur_device_handle_t Device, platform_impl &Platform,
: get_info_impl<UR_DEVICE_INFO_PARENT_DEVICE>()),
// TODO catch an exception and put it to list of asynchronous exceptions:
MCache{*this} {
// Interoperability Constructor already calls DeviceRetain in
// urDeviceCreateWithNativeHandle.
getAdapter().call<UrApiKind::urDeviceRetain>(MDevice);
// urDeviceRetain(MDevice) should not be called here,
// because RefCounter is initialized with 1,
// when the device is created.
}

device_impl::~device_impl() {
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9 changes: 2 additions & 7 deletions sycl/unittests/context_device/DeviceRefCounter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -43,12 +43,7 @@ TEST(DevRefCounter, DevRefCounter) {
sycl::platform Plt = sycl::platform();

Plt.get_devices();
EXPECT_NE(DevRefCounter, 0);
// This is the behavior that SYCL performs at shutdown, but there
// are timing differences Lin/Win and shared/static that make
// it not map correctly into our mock.
// So for this test, we just do it.
sycl::detail::GlobalHandler::instance().getPlatformCache().clear();

EXPECT_EQ(DevRefCounter, 0);
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@againull againull Sep 23, 2025 •
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It seems a bit off that ref count is zero here, because callback for urDeviceGet (redefinedDevicesGetAfter) increments the DevRefCounter. So, even if we don't call Retain anymore, ref count is still expected to be at least 1 because of urDevicesGet. It would be nice to either understand why it is normal to have zero ref count here or to update the test if necessary if there is something wrong.

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@againull I have debugged this unittest. It calls 3 times platform_impl::getDevicesImplHelper():

llvm/sycl/source/detail/platform_impl.cpp

Line 497 in 6b29cf1

void platform_impl::getDevicesImplHelper(ur_device_type_t UrDeviceType,
which calls:

  1. urDeviceGet(NumDevices == 0) what sets DevRefCounter == 0 (using redefinedDevicesGetAfter()):

    llvm/sycl/source/detail/platform_impl.cpp

    Lines 502 to 504 in 6b29cf1

    MAdapter->call<UrApiKind::urDeviceGet>(MPlatform, UrDeviceType,
    0u, // CP info::device_type::all
    nullptr, &NumDevices);
  2. urDeviceGet(NumDevices == 1) what sets DevRefCounter == 1 (using redefinedDevicesGetAfter()):

    llvm/sycl/source/detail/platform_impl.cpp

    Lines 527 to 530 in 6b29cf1

    MAdapter->call<UrApiKind::urDeviceGet>(
    MPlatform,
    UrDeviceType, // CP info::device_type::all
    NumDevices, UrDevices.data(), nullptr);
  3. urDeviceRelease() on this device what decrements DevRefCounter to 0 (using redefinedDeviceReleaseAfter()):

    llvm/sycl/source/detail/platform_impl.cpp

    Lines 560 to 563 in 6b29cf1

    // The reference counter for handles, that we used to create sycl objects, is
    // incremented, so we need to call release here.
    for (ur_device_handle_t &UrDev : UrDevicesToCleanUp)
    MAdapter->call<UrApiKind::urDeviceRelease>(UrDev);

... what looks like:

- redefinedDevicesGetAfter(*params.pphDevices == 0)    DevRefCounter == 0  from urDeviceGet(NumDevices == 0)
- redefinedDevicesGetAfter(*params.pNumEntries == 1)   DevRefCounter == 1  from urDeviceGet(NumDevices == 1)
- redefinedDeviceReleaseAfter()                        DevRefCounter == 0  from urDeviceRelease()

- redefinedDevicesGetAfter(*params.pphDevices == 0)    DevRefCounter == 0  from urDeviceGet(NumDevices == 0)
- redefinedDevicesGetAfter(*params.pNumEntries == 1)   DevRefCounter == 1  from urDeviceGet(NumDevices == 1)
- redefinedDeviceReleaseAfter()                        DevRefCounter == 0  from urDeviceRelease()

- redefinedDevicesGetAfter(*params.pphDevices == 0)    DevRefCounter == 0  from urDeviceGet(NumDevices == 0)
- redefinedDevicesGetAfter(*params.pNumEntries == 1)   DevRefCounter == 1  from urDeviceGet(NumDevices == 1)
- redefinedDeviceReleaseAfter()                        DevRefCounter == 0  from urDeviceRelease()

@againull Does it make sense or is there anything wrong here?

}
EXPECT_EQ(DevRefCounter, 0);
}