Add a refcount to dl load() and close() calls

gen/nvml/lib.go

@@ -38,9 +38,10 @@ var errLibraryAlreadyLoaded = errors.New("library already loaded")
 // This includes a reference to the underlying DynamicLibrary
 type library struct {
 	sync.Mutex
-	path  string
-	flags int
-	dl    dynamicLibrary
+	path     string
+	flags    int
+	refcount refcount
+	dl       dynamicLibrary
 }
 
 // libnvml is a global instance of the nvml library.
@@ -77,16 +78,17 @@ var newDynamicLibrary = func(path string, flags int) dynamicLibrary {
 
 // load initializes the library and updates the versioned symbols.
 // Multiple calls to an already loaded library will return without error.
-func (l *library) load() error {
+func (l *library) load() (rerr error) {
 	l.Lock()
 	defer l.Unlock()
-	if l.dl != nil {
+
+	defer func() { l.refcount.IncOnNoError(rerr) }()
+	if l.refcount > 0 {
 		return nil
 	}
 
 	dl := newDynamicLibrary(l.path, l.flags)
-	err := dl.Open()
-	if err != nil {
+	if err := dl.Open(); err != nil {
 		return fmt.Errorf("error opening %s: %w", l.path, err)
 	}
 
@@ -99,16 +101,16 @@ func (l *library) load() error {
 // close the underlying library and ensure that the global pointer to the
 // library is set to nil to ensure that subsequent calls to open will reinitialize it.
 // Multiple calls to an already closed nvml library will return without error.
-func (l *library) close() error {
+func (l *library) close() (rerr error) {
 	l.Lock()
 	defer l.Unlock()
 
-	if l.dl == nil {
+	defer func() { l.refcount.DecOnNoError(rerr) }()
+	if l.refcount != 1 {
 		return nil
 	}
 
-	err := l.dl.Close()
-	if err != nil {
+	if err := l.dl.Close(); err != nil {
 		return fmt.Errorf("error closing %s: %w", l.path, err)
 	}
 

gen/nvml/lib_test.go

@@ -134,6 +134,117 @@ func TestLookupFromDefault(t *testing.T) {
 	}
 }
 
+func TestLoadAndCloseNesting(t *testing.T) {
+	dl := &dynamicLibraryMock{
+		OpenFunc: func() error {
+			return nil
+		},
+		CloseFunc: func() error {
+			return nil
+		},
+	}
+
+	defer setNewDynamicLibraryDuringTest(dl)()
+	defer resetLibrary()
+
+	// When calling close before opening the library nothing happens.
+	require.Equal(t, 0, len(dl.calls.Close))
+	require.Nil(t, libnvml.close())
+	require.Equal(t, 0, len(dl.calls.Close))
+
+	// When calling load twice, the library was only opened once
+	require.Equal(t, 0, len(dl.calls.Open))
+	require.Nil(t, libnvml.load())
+	require.Equal(t, 1, len(dl.calls.Open))
+	require.Nil(t, libnvml.load())
+	require.Equal(t, 1, len(dl.calls.Open))
+
+	// Only after calling close twice, was the library closed
+	require.Equal(t, 0, len(dl.calls.Close))
+	require.Nil(t, libnvml.close())
+	require.Equal(t, 0, len(dl.calls.Close))
+	require.Nil(t, libnvml.close())
+	require.Equal(t, 1, len(dl.calls.Close))
+
+	// Calling close again doesn't attempt to close the library again
+	require.Nil(t, libnvml.close())
+	require.Equal(t, 1, len(dl.calls.Close))
+}
+
+func TestLoadAndCloseWithErrors(t *testing.T) {
+	testCases := []struct {
+		description           string
+		dl                    dynamicLibrary
+		expectedLoadRefcount  refcount
+		expectedCloseRefcount refcount
+	}{
+		{
+			description: "regular flow",
+			dl: &dynamicLibraryMock{
+				OpenFunc: func() error {
+					return nil
+				},
+				CloseFunc: func() error {
+					return nil
+				},
+			},
+			expectedLoadRefcount:  1,
+			expectedCloseRefcount: 0,
+		},
+		{
+			description: "open error",
+			dl: &dynamicLibraryMock{
+				OpenFunc: func() error {
+					return errors.New("")
+				},
+				CloseFunc: func() error {
+					return nil
+				},
+			},
+			expectedLoadRefcount:  0,
+			expectedCloseRefcount: 0,
+		},
+		{
+			description: "close error",
+			dl: &dynamicLibraryMock{
+				OpenFunc: func() error {
+					return nil
+				},
+				CloseFunc: func() error {
+					return errors.New("")
+				},
+			},
+			expectedLoadRefcount:  1,
+			expectedCloseRefcount: 1,
+		},
+		{
+			description: "open and close error",
+			dl: &dynamicLibraryMock{
+				OpenFunc: func() error {
+					return errors.New("")
+				},
+				CloseFunc: func() error {
+					return errors.New("")
+				},
+			},
+			expectedLoadRefcount:  0,
+			expectedCloseRefcount: 0,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			defer setNewDynamicLibraryDuringTest(tc.dl)()
+			defer resetLibrary()
+
+			_ = libnvml.load()
+			require.Equal(t, tc.expectedLoadRefcount, libnvml.refcount)
+			_ = libnvml.close()
+			require.Equal(t, tc.expectedCloseRefcount, libnvml.refcount)
+		})
+	}
+}
+
 func setNewDynamicLibraryDuringTest(dl dynamicLibrary) func() {
 	original := newDynamicLibrary
 	newDynamicLibrary = func(string, int) dynamicLibrary {

gen/nvml/refcount.go

@@ -0,0 +1,31 @@
+/**
+# Copyright 2024 NVIDIA CORPORATION
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package nvml
+
+type refcount int
+
+func (r *refcount) IncOnNoError(err error) {
+	if err == nil {
+		(*r)++
+	}
+}
+
+func (r *refcount) DecOnNoError(err error) {
+	if err == nil && (*r) > 0 {
+		(*r)--
+	}
+}

gen/nvml/refcount_test.go

@@ -0,0 +1,139 @@
+/**
+# Copyright 2023 NVIDIA CORPORATION
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package nvml
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRefcount(t *testing.T) {
+	testCases := []struct {
+		description      string
+		workload         func(r *refcount)
+		expectedRefcount refcount
+	}{
+		{
+			description:      "No inc or dec",
+			workload:         func(r *refcount) {},
+			expectedRefcount: refcount(0),
+		},
+		{
+			description: "Single inc, no error",
+			workload: func(r *refcount) {
+				r.IncOnNoError(nil)
+			},
+			expectedRefcount: refcount(1),
+		},
+		{
+			description: "Single inc, with error",
+			workload: func(r *refcount) {
+				r.IncOnNoError(errors.New(""))
+			},
+			expectedRefcount: refcount(0),
+		},
+		{
+			description: "Double inc, no error",
+			workload: func(r *refcount) {
+				r.IncOnNoError(nil)
+				r.IncOnNoError(nil)
+			},
+			expectedRefcount: refcount(2),
+		},
+		{
+			description: "Double inc, one with error",
+			workload: func(r *refcount) {
+				r.IncOnNoError(nil)
+				r.IncOnNoError(errors.New(""))
+			},
+			expectedRefcount: refcount(1),
+		},
+		{
+			description: "Single dec, no error",
+			workload: func(r *refcount) {
+				r.DecOnNoError(nil)
+			},
+			expectedRefcount: refcount(0),
+		},
+		{
+			description: "Single dec, with error",
+			workload: func(r *refcount) {
+				r.DecOnNoError(errors.New(""))
+			},
+			expectedRefcount: refcount(0),
+		},
+		{
+			description: "Single inc, single dec, no errors",
+			workload: func(r *refcount) {
+				r.IncOnNoError(nil)
+				r.DecOnNoError(nil)
+			},
+			expectedRefcount: refcount(0),
+		},
+		{
+			description: "Double inc, Double dec, no errors",
+			workload: func(r *refcount) {
+				r.IncOnNoError(nil)
+				r.IncOnNoError(nil)
+				r.DecOnNoError(nil)
+				r.DecOnNoError(nil)
+			},
+			expectedRefcount: refcount(0),
+		},
+		{
+			description: "Double inc, Double dec, one inc error",
+			workload: func(r *refcount) {
+				r.IncOnNoError(nil)
+				r.IncOnNoError(errors.New(""))
+				r.DecOnNoError(nil)
+				r.DecOnNoError(nil)
+			},
+			expectedRefcount: refcount(0),
+		},
+		{
+			description: "Double inc, Double dec, one dec error",
+			workload: func(r *refcount) {
+				r.IncOnNoError(nil)
+				r.IncOnNoError(nil)
+				r.DecOnNoError(nil)
+				r.DecOnNoError(errors.New(""))
+			},
+			expectedRefcount: refcount(1),
+		},
+		{
+			description: "Double inc, Tripple dec, one dec error early on",
+			workload: func(r *refcount) {
+				r.IncOnNoError(nil)
+				r.IncOnNoError(nil)
+				r.DecOnNoError(errors.New(""))
+				r.DecOnNoError(nil)
+				r.DecOnNoError(nil)
+			},
+			expectedRefcount: refcount(0),
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			var r refcount
+			tc.workload(&r)
+			require.Equal(t, tc.expectedRefcount, r)
+		})
+	}
+}