Make much of the proxy thread-safe with 1 great big lock.

ppapi/proxy/ppb_var_unittest.cc

Index: ppapi/proxy/ppb_var_unittest.cc
diff --git a/ppapi/proxy/ppb_var_unittest.cc b/ppapi/proxy/ppb_var_unittest.cc
index 79abf39b79b1eae4ba3012862128d1d59a5d0149..16683d939d2fe9c537801ec46542c96085c6473f 100644
--- a/ppapi/proxy/ppb_var_unittest.cc
+++ b/ppapi/proxy/ppb_var_unittest.cc
@@ -6,20 +6,21 @@
 #include <vector>
 
 #include "base/string_number_conversions.h"
+#include "base/threading/platform_thread.h"
 #include "ppapi/c/pp_var.h"
 #include "ppapi/c/ppb_var.h"
 #include "ppapi/proxy/ppapi_proxy_test.h"
 #include "ppapi/proxy/ppb_var_proxy.h"
 
-// TODO(dmichael): Make PPB_Var_Proxy and PluginResourceTracker thread-safe and
-// add thread-safety tests here.
-
 namespace {
 std::string VarToString(const PP_Var& var, const PPB_Var* ppb_var) {
   uint32_t len = 0;
   const char* utf8 = ppb_var->VarToUtf8(var, &len);
   return std::string(utf8, len);
 }
+const size_t kNumStrings = 100;
+const size_t kNumThreads = 20;
+const int kRefsToAdd = 20;
 }  // namespace
 
 namespace ppapi {
@@ -27,46 +28,216 @@ namespace proxy {
 
 class PPB_VarTest : public PluginProxyTest {
  public:
-  PPB_VarTest() {}
+  PPB_VarTest()
+      : test_strings_(kNumStrings), vars_(kNumStrings),
+        ppb_var_(GetPPB_Var_Interface()) {
+    // Set the value of test_strings_[i] to "i".
+    for (size_t i = 0; i < kNumStrings; ++i)
+      test_strings_[i] = base::IntToString(i);
+  }
+ protected:
+  std::vector<std::string> test_strings_;
+  std::vector<PP_Var> vars_;
+  const PPB_Var* ppb_var_;
 };
 
+// Test basic String operations.
 TEST_F(PPB_VarTest, Strings) {
-  const PPB_Var* ppb_var = GetPPB_Var_Interface();
-
-  // Make a vector of strings, where the value of test_strings[i] is "i".
-  const int kNumStrings = 5;
-  std::vector<std::string> test_strings(kNumStrings);
-  for (int i = 0; i < kNumStrings; ++i)
-    test_strings[i] = base::IntToString(i);
-
-  std::vector<PP_Var> vars(kNumStrings);
-  for (int i = 0; i < kNumStrings; ++i) {
-    vars[i] = ppb_var->VarFromUtf8(pp_module(),
-                                   test_strings[i].c_str(),
-                                   test_strings[i].length());
-    EXPECT_EQ(test_strings[i], VarToString(vars[i], ppb_var));
+  for (size_t i = 0; i < kNumStrings; ++i) {
+    vars_[i] = ppb_var_->VarFromUtf8(pp_module(),
+                                   test_strings_[i].c_str(),
+                                   test_strings_[i].length());
+    EXPECT_EQ(test_strings_[i], VarToString(vars_[i], ppb_var_));
   }
   // At this point, they should each have a ref count of 1. Add some more.
-  const int kRefsToAdd = 3;
   for (int ref = 0; ref < kRefsToAdd; ++ref) {
-    for (int i = 0; i < kNumStrings; ++i) {
-      ppb_var->AddRef(vars[i]);
+    for (size_t i = 0; i < kNumStrings; ++i) {
+      ppb_var_->AddRef(vars_[i]);
       // Make sure the string is still there with the right value.
-      EXPECT_EQ(test_strings[i], VarToString(vars[i], ppb_var));
+      EXPECT_EQ(test_strings_[i], VarToString(vars_[i], ppb_var_));
     }
   }
   for (int ref = 0; ref < kRefsToAdd; ++ref) {
-    for (int i = 0; i < kNumStrings; ++i) {
-      ppb_var->Release(vars[i]);
+    for (size_t i = 0; i < kNumStrings; ++i) {
+      ppb_var_->Release(vars_[i]);
       // Make sure the string is still there with the right value.
-      EXPECT_EQ(test_strings[i], VarToString(vars[i], ppb_var));
+      EXPECT_EQ(test_strings_[i], VarToString(vars_[i], ppb_var_));
     }
   }
   // Now remove the ref counts for each string and make sure they are gone.
-  for (int i = 0; i < kNumStrings; ++i) {
-    ppb_var->Release(vars[i]);
+  for (size_t i = 0; i < kNumStrings; ++i) {
+    ppb_var_->Release(vars_[i]);
+    uint32_t len = 10;
+    const char* utf8 = ppb_var_->VarToUtf8(vars_[i], &len);
+    EXPECT_EQ(NULL, utf8);
+    EXPECT_EQ(0u, len);
+  }
+}
+
+// PPB_VarTest.Threads tests string operations accessed by multiple threads.
+namespace {
+// These three delegate classes which precede the test are for use with
+// PlatformThread. The test goes roughly like this:
+// 1) Spawn kNumThreads 'CreateVar' threads, giving each a roughly equal subset
+//    of test_strings_ to 'create'. Each 'CreateVar' thread also converts its
+//    set of vars back in to strings so that the main test thread can verify
+//    their values were correctly converted.
+// 2) Spawn kNumThreads 'ChangeRefVar' threads. Each of these threads will
+//    incremement & decrement the reference count of ALL vars kRefsToAdd times.
+//    Finally, each thread adds 1 ref count. This leaves each var with a ref-
+//    count of |kNumThreads + 1|. The main test thread removes a ref, leaving
+//    each var with a ref-count of |kNumThreads|.
+// 3) Spawn kNumThreads 'RemoveVar' threads. Each of these threads releases each
+//    var once. Once all the threads have finished, there should be no vars
+//    left.
+class CreateVarThreadDelegate : public base::PlatformThread::Delegate {
+ public:
+  // |strings_in|, |vars|, and |strings_out| are arrays, and size is their size.
+  // For each |strings_in[i]|, we will set |vars[i]| using that value. Then we
+  // read the var back out to |strings_out[i]|.
+  CreateVarThreadDelegate(PP_Module pp_module, const std::string* strings_in,
+                          PP_Var* vars_out, std::string* strings_out,
+                          size_t size)
+      : pp_module_(pp_module), strings_in_(strings_in), vars_out_(vars_out),
+        strings_out_(strings_out), size_(size) {
+  }
+  virtual ~CreateVarThreadDelegate() {}
+  virtual void ThreadMain() {
+    const PPB_Var* ppb_var = ppapi::proxy::GetPPB_Var_Interface();
+    for (size_t i = 0; i < size_; ++i) {
+      vars_out_[i] = ppb_var->VarFromUtf8(pp_module_,
+                                          strings_in_[i].c_str(),
+                                          strings_in_[i].length());
+      strings_out_[i] = VarToString(vars_out_[i], ppb_var);
+    }
+  }
+ private:
+  PP_Module pp_module_;
+  const std::string* strings_in_;
+  PP_Var* vars_out_;
+  std::string* strings_out_;
+  size_t size_;
+};
+
+// A thread that will increment and decrement the reference count of every var
+// multiple times.
+class ChangeRefVarThreadDelegate : public base::PlatformThread::Delegate {
+ public:
+  ChangeRefVarThreadDelegate(const std::vector<PP_Var>& vars) : vars_(vars) {
+  }
+  virtual ~ChangeRefVarThreadDelegate() {}
+  virtual void ThreadMain() {
+    const PPB_Var* ppb_var = ppapi::proxy::GetPPB_Var_Interface();
+    // Increment and decrement the reference count for each var kRefsToAdd
+    // times. Note that we always AddRef once before doing the matching Release,
+    // to ensure that we never accidentally release the last reference.
+    for (int ref = 0; ref < kRefsToAdd; ++ref) {
+      for (size_t i = 0; i < kNumStrings; ++i) {
+        ppb_var->AddRef(vars_[i]);
+        ppb_var->Release(vars_[i]);
+      }
+    }
+    // Now add 1 ref to each Var. The net result is that all Vars will have a
+    // ref-count of (kNumThreads + 1) after this. That will allow us to have all
+    // threads release all vars later.
+    for (size_t i = 0; i < kNumStrings; ++i) {
+      ppb_var->AddRef(vars_[i]);
+    }
+  }
+ private:
+  std::vector<PP_Var> vars_;
+};
+
+// A thread that will decrement the reference count of every var once.
+class RemoveRefVarThreadDelegate : public base::PlatformThread::Delegate {
+ public:
+  RemoveRefVarThreadDelegate(const std::vector<PP_Var>& vars) : vars_(vars) {
+  }
+  virtual ~RemoveRefVarThreadDelegate() {}
+  virtual void ThreadMain() {
+    const PPB_Var* ppb_var = ppapi::proxy::GetPPB_Var_Interface();
+    for (size_t i = 0; i < kNumStrings; ++i) {
+      ppb_var->Release(vars_[i]);
+    }
+  }
+ private:
+  std::vector<PP_Var> vars_;
+};
+
+}  // namespace
+
+#ifdef ENABLE_PEPPER_THREADING
+TEST_F(PPB_VarTest, Threads) {
+#else
+TEST_F(PPB_VarTest, DISABLED_Threads) {
+#endif
+  std::vector<base::PlatformThreadHandle> create_var_threads(kNumThreads);
+  std::vector<CreateVarThreadDelegate> create_var_delegates;
+  // The strings that the threads will re-extract from Vars (so we can check
+  // that they match the original strings).
+  std::vector<std::string> strings_out(kNumStrings);
+  size_t strings_per_thread = kNumStrings/kNumThreads;
+  // Give each thread an equal slice of strings to turn in to vars. (Except the
+  // last thread may get fewer if kNumStrings is not evenly divisible by
+  // kNumThreads).
+  for (size_t slice_start= 0; slice_start < kNumStrings;
+       slice_start += strings_per_thread) {
+    create_var_delegates.push_back(
+        CreateVarThreadDelegate(pp_module(),
+                                &test_strings_[slice_start],
+                                &vars_[slice_start],
+                                &strings_out[slice_start],
+                                std::min(strings_per_thread,
+                                         kNumStrings - slice_start)));
+  }
+  // Now run then join all the threads.
+  for (size_t i = 0; i < kNumThreads; ++i)
+    base::PlatformThread::Create(0, &create_var_delegates[i],
+                                 &create_var_threads[i]);
+  for (size_t i = 0; i < kNumThreads; ++i)
+    base::PlatformThread::Join(create_var_threads[i]);
+  // Now check that the strings have the expected values.
+  EXPECT_EQ(test_strings_, strings_out);
+
+  // Tinker with the reference counts in a multithreaded way.
+  std::vector<base::PlatformThreadHandle> change_ref_var_threads(kNumThreads);
+  std::vector<ChangeRefVarThreadDelegate> change_ref_var_delegates;
+  for (size_t i = 0; i < kNumThreads; ++i)
+    change_ref_var_delegates.push_back(ChangeRefVarThreadDelegate(vars_));
+  for (size_t i = 0; i < kNumThreads; ++i) {
+    base::PlatformThread::Create(0, &change_ref_var_delegates[i],
+                                 &change_ref_var_threads[i]);
+  }
+  for (size_t i = 0; i < kNumThreads; ++i)
+    base::PlatformThread::Join(change_ref_var_threads[i]);
+
+  // Now each var has a refcount of (kNumThreads + 1). Let's decrement each var
+  // once so that every 'RemoveRef' thread (spawned below) owns 1 reference, and
+  // when the last one removes a ref, the Var will be deleted.
+  for (size_t i = 0; i < kNumStrings; ++i) {
+    ppb_var_->Release(vars_[i]);
+  }
+
+  // Check that all vars are still valid and have the values we expect.
+  for (size_t i = 0; i < kNumStrings; ++i)
+    EXPECT_EQ(test_strings_[i], VarToString(vars_[i], ppb_var_));
+
+  // Remove the last reference counts for all vars.
+  std::vector<base::PlatformThreadHandle> remove_ref_var_threads(kNumThreads);
+  std::vector<RemoveRefVarThreadDelegate> remove_ref_var_delegates;
+  for (size_t i = 0; i < kNumThreads; ++i)
+    remove_ref_var_delegates.push_back(RemoveRefVarThreadDelegate(vars_));
+  for (size_t i = 0; i < kNumThreads; ++i) {
+    base::PlatformThread::Create(0, &remove_ref_var_delegates[i],
+                                 &remove_ref_var_threads[i]);
+  }
+  for (size_t i = 0; i < kNumThreads; ++i)
+    base::PlatformThread::Join(remove_ref_var_threads[i]);
+
+  // All the vars should no longer represent valid strings.
+  for (size_t i = 0; i < kNumStrings; ++i) {
     uint32_t len = 10;
-    const char* utf8 = ppb_var->VarToUtf8(vars[i], &len);
+    const char* utf8 = ppb_var_->VarToUtf8(vars_[i], &len);
     EXPECT_EQ(NULL, utf8);
     EXPECT_EQ(0u, len);
   }