Bug 1340928 (part 5) - Pass the interval to PlatformStart(). r=mstange.

This avoids the need for platform-linux-android.cpp to read gInterval off the
main thread in an awkward spot. It also makes platform-linux-android.cpp
more like platform-{win32,macos}.cpp.

--HG--
extra : rebase_source : c1c76a382d6373f9fd2e3f89a1e1f8fef9072257

tools/profiler/core/platform-linux-android.cpp

@@ -145,6 +145,8 @@ static void* setup_atfork() {
 }
 #endif /* !defined(GP_OS_android) */
 
+static int gIntervalMicro;
+
 // Global variables through which data is sent from SigprofSender() to
 // SigprofHandler(). gSignalHandlingDone provides inter-thread synchronization.
 static ThreadInfo* gCurrentThreadInfo;
@@ -342,11 +344,8 @@ SigprofSender(void* aArg)
 #endif
     }
 
-    // This off-main-thread use of gInterval is safe due to implicit
-    // synchronization -- this function cannot run at the same time as
-    // profiler_{start,stop}(), where gInterval is set.
     TimeStamp targetSleepEndTime =
-      sampleStart + TimeDuration::FromMicroseconds(gInterval * 1000);
+      sampleStart + TimeDuration::FromMicroseconds(gIntervalMicro);
     TimeStamp beforeSleep = TimeStamp::Now();
     TimeDuration targetSleepDuration = targetSleepEndTime - beforeSleep;
     double sleepTime = std::max(0.0, (targetSleepDuration - lastSleepOverhead).ToMicroseconds());
@@ -358,7 +357,7 @@ SigprofSender(void* aArg)
 }
 
 static void
-PlatformStart()
+PlatformStart(double aInterval)
 {
   MOZ_RELEASE_ASSERT(NS_IsMainThread());
 
@@ -372,6 +371,11 @@ PlatformStart()
   }
 #endif
 
+  gIntervalMicro = floor(aInterval * 1000 + 0.5);
+  if (gIntervalMicro <= 0) {
+    gIntervalMicro = 1;
+  }
+
   // Initialize signal handler communication
   gCurrentThreadInfo = nullptr;
   gRssMemory = 0;
@@ -426,6 +430,8 @@ PlatformStop()
   MOZ_ASSERT(gIsActive);
   gIsActive = false;
 
+  gIntervalMicro = 0;
+
   // Wait for signal sender termination (it will exit after setting
   // active_ to false).
   if (gHasSigprofSenderLaunched) {

tools/profiler/core/platform-macos.cpp

@@ -80,8 +80,8 @@ PlatformDataDestructor::operator()(PlatformData* aData)
 class SamplerThread
 {
 public:
-  explicit SamplerThread(double interval)
-    : mIntervalMicro(floor(interval * 1000 + 0.5))
+  explicit SamplerThread(double aInterval)
+    : mIntervalMicro(floor(aInterval * 1000 + 0.5))
   {
     if (mIntervalMicro <= 0) {
       mIntervalMicro = 1;
@@ -120,12 +120,12 @@ public:
     pthread_join(mThread, NULL);
   }
 
-  static void StartSampler() {
+  static void StartSampler(double aInterval) {
     MOZ_RELEASE_ASSERT(NS_IsMainThread());
     MOZ_RELEASE_ASSERT(!mInstance);
 
     if (mInstance == NULL) {
-      mInstance = new SamplerThread(gInterval);
+      mInstance = new SamplerThread(aInterval);
       mInstance->Start();
     }
   }
@@ -261,13 +261,13 @@ PlatformInit()
 }
 
 static void
-PlatformStart()
+PlatformStart(double aInterval)
 {
   MOZ_RELEASE_ASSERT(NS_IsMainThread());
 
   MOZ_ASSERT(!gIsActive);
   gIsActive = true;
-  SamplerThread::StartSampler();
+  SamplerThread::StartSampler(aInterval);
 }
 
 static void

tools/profiler/core/platform-win32.cpp

@@ -87,11 +87,10 @@ static const HANDLE kNoThread = INVALID_HANDLE_VALUE;
 class SamplerThread
 {
  public:
-  explicit SamplerThread(double interval)
+  explicit SamplerThread(double aInterval)
     : mThread(kNoThread)
-    , mInterval(interval)
+    , mInterval(floor(aInterval + 0.5))
   {
-    mInterval = floor(interval + 0.5);
     if (mInterval <= 0) {
       mInterval = 1;
     }
@@ -129,11 +128,11 @@ class SamplerThread
     }
   }
 
-  static void StartSampler() {
+  static void StartSampler(double aInterval) {
     MOZ_RELEASE_ASSERT(NS_IsMainThread());
     MOZ_RELEASE_ASSERT(!mInstance);
 
-    mInstance = new SamplerThread(gInterval);
+    mInstance = new SamplerThread(aInterval);
     mInstance->Start();
   }
 
@@ -273,13 +272,13 @@ PlatformInit()
 }
 
 static void
-PlatformStart()
+PlatformStart(double aInterval)
 {
   MOZ_RELEASE_ASSERT(NS_IsMainThread());
 
   MOZ_ASSERT(!gIsActive);
   gIsActive = true;
-  SamplerThread::StartSampler();
+  SamplerThread::StartSampler(aInterval);
 }
 
 static void

tools/profiler/core/platform.cpp

@@ -122,11 +122,7 @@ static Vector<std::string> gFeatures;
 // All accesses to gEntrySize are on the main thread, so no locking is needed.
 static int gEntrySize = 0;
 
-// This variable is set on the main thread in profiler_{start,stop}(), and
-// mostly read on the main thread. There is one read off the main thread in
-// SigprofSender() in platform-linux.cc which is safe because there is implicit
-// synchronization between that function and the set points in
-// profiler_{start,stop}().
+// All accesses to gInterval are on the main thread, so no locking is needed.
 static double gInterval = 0;
 
 // XXX: These two variables are used extensively both on and off the main
@@ -1591,7 +1587,7 @@ RegisterCurrentThread(const char* aName, PseudoStack* aPseudoStack,
 
 // Platform-specific init/start/stop actions.
 static void PlatformInit();
-static void PlatformStart();
+static void PlatformStart(double aInterval);
 static void PlatformStop();
 
 void
@@ -2032,7 +2028,7 @@ profiler_start(int aProfileEntries, double aInterval,
   gGatherer = new mozilla::ProfileGatherer();
 
   MOZ_ASSERT(!gIsActive && !gIsPaused);
-  PlatformStart();
+  PlatformStart(gInterval);
   MOZ_ASSERT(gIsActive && !gIsPaused);  // PlatformStart() sets gIsActive.
 
   if (gProfileJS || privacyMode) {