Fix data race on mTestIndex. (#7494)

We could end up sending a message and getting a response to it before we ever incremented mTestIndex (if our call into NextTest() was on a thread other than the message thread). If that happened, we would end up running some subtest twice, and then later whenever we incrememented mTestIndex would end up skipping some subtest. Fixes #7493
project-chip · Aug 31, 2021 · 3689594 · 3689594
1 parent a0cf78f
commit 3689594
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Showing 2 changed files with 24 additions and 15 deletions.
diff --git a/examples/chip-tool/commands/tests/Commands.h b/examples/chip-tool/commands/tests/Commands.h
@@ -24,7 +24,7 @@
 class TestCluster : public TestCommand
 {
 public:
-    TestCluster() : TestCommand("TestCluster") {}
+    TestCluster() : TestCommand("TestCluster"), mTestIndex(0) {}
 
     /////////// TestCommand Interface /////////
     CHIP_ERROR NextTest() override
@@ -37,7 +37,11 @@ class TestCluster : public TestCommand
             SetCommandExitStatus(true);
         }
 
-        switch (mTestIndex)
+        // Ensure we increment mTestIndex before we start running the relevant
+        // command.  That way if we lose the timeslice after we send the message
+        // but before our function call returns, we won't end up with an
+        // incorrect mTestIndex value observed when we get the response.
+        switch (mTestIndex++)
         {
         case 0:
             err = TestSendClusterTestClusterCommandTest_0();
@@ -55,7 +59,6 @@ class TestCluster : public TestCommand
             err = TestSendClusterTestClusterCommandReadAttribute_4();
             break;
         }
-        mTestIndex++;
 
         if (CHIP_NO_ERROR != err)
         {
@@ -67,8 +70,8 @@ class TestCluster : public TestCommand
     }
 
 private:
-    uint16_t mTestIndex = 0;
-    uint16_t mTestCount = 5;
+    std::atomic_uint16_t mTestIndex;
+    const uint16_t mTestCount = 5;
 
     //
     // Tests methods
@@ -437,7 +440,7 @@ class TestCluster : public TestCommand
 class OnOffCluster : public TestCommand
 {
 public:
-    OnOffCluster() : TestCommand("OnOffCluster") {}
+    OnOffCluster() : TestCommand("OnOffCluster"), mTestIndex(0) {}
 
     /////////// TestCommand Interface /////////
     CHIP_ERROR NextTest() override
@@ -450,7 +453,11 @@ class OnOffCluster : public TestCommand
             SetCommandExitStatus(true);
         }
 
-        switch (mTestIndex)
+        // Ensure we increment mTestIndex before we start running the relevant
+        // command.  That way if we lose the timeslice after we send the message
+        // but before our function call returns, we won't end up with an
+        // incorrect mTestIndex value observed when we get the response.
+        switch (mTestIndex++)
         {
         case 0:
             err = TestSendClusterOnOffCommandReadAttribute_0();
@@ -468,7 +475,6 @@ class OnOffCluster : public TestCommand
             err = TestSendClusterOnOffCommandReadAttribute_4();
             break;
         }
-        mTestIndex++;
 
         if (CHIP_NO_ERROR != err)
         {
@@ -480,8 +486,8 @@ class OnOffCluster : public TestCommand
     }
 
 private:
-    uint16_t mTestIndex = 0;
-    uint16_t mTestCount = 5;
+    std::atomic_uint16_t mTestIndex;
+    const uint16_t mTestCount = 5;
 
     //
     // Tests methods

diff --git a/examples/chip-tool/templates/partials/test_cluster.zapt b/examples/chip-tool/templates/partials/test_cluster.zapt
@@ -2,7 +2,7 @@
 class {{asCamelCased filename false}}: public TestCommand
 {
   public:
-    {{asCamelCased filename false}}(): TestCommand("{{filename}}") {}
+    {{asCamelCased filename false}}(): TestCommand("{{filename}}"), mTestIndex(0) {}
 
     /////////// TestCommand Interface /////////
     CHIP_ERROR NextTest() override
@@ -15,15 +15,18 @@ class {{asCamelCased filename false}}: public TestCommand
           SetCommandExitStatus(true);
       }
 
-      switch (mTestIndex)
+      // Ensure we increment mTestIndex before we start running the relevant
+      // command.  That way if we lose the timeslice after we send the message
+      // but before our function call returns, we won't end up with an
+      // incorrect mTestIndex value observed when we get the response.
+      switch (mTestIndex++)
       {
         {{#chip_tests_items}}
         case {{index}}:
           err = TestSendCluster{{asCamelCased cluster false}}Command{{asCamelCased command false}}_{{index}}();
           break;
         {{/chip_tests_items}}
       }
-      mTestIndex++;
 
       if (CHIP_NO_ERROR != err)
       {
@@ -36,8 +39,8 @@ class {{asCamelCased filename false}}: public TestCommand
 
 
   private:
-    uint16_t mTestIndex = 0;
-    uint16_t mTestCount = {{totalTests}};
+    std::atomic_uint16_t mTestIndex;
+    const uint16_t mTestCount = {{totalTests}};
 
     //
     // Tests methods