Improve fbsystrace support

Reviewed By: mhorowitz

Differential Revision: D4756318

fbshipit-source-id: 7811f680a7ad044b5ae028ee9b2fed5f46ce2a63

Author: javache

React/Base/RCTBridge.m

@@ -301,15 +301,6 @@ - (Class)bridgeClass
   }
 
   RCTAssert(implClass != nil, @"No bridge implementation is available, giving up.");
-
-#ifdef WITH_FBSYSTRACE
-  if (implClass == cxxBridgeClass) {
-    [RCTFBSystrace registerCallbacks];
-  } else {
-    [RCTFBSystrace unregisterCallbacks];
-  }
-#endif
-
   return implClass;
 }
 

React/CxxBridge/RCTCxxBridge.mm

@@ -1139,6 +1139,9 @@ - (void)startProfiling
   RCTAssertMainQueue();
 
   [self executeBlockOnJavaScriptThread:^{
+    #if WITH_FBSYSTRACE
+    [RCTFBSystrace registerCallbacks];
+    #endif
     RCTProfileInit(self);
   }];
 }
@@ -1151,6 +1154,9 @@ - (void)stopProfiling:(void (^)(NSData *))callback
     RCTProfileEnd(self, ^(NSString *log) {
       NSData *logData = [log dataUsingEncoding:NSUTF8StringEncoding];
       callback(logData);
+      #if WITH_FBSYSTRACE
+      [RCTFBSystrace unregisterCallbacks];
+      #endif
     });
   }];
 }

React/Profiler/RCTProfile.h

@@ -175,7 +175,7 @@ typedef struct {
 } systrace_arg_t;
 
 typedef struct {
-  void (*start)(uint64_t enabledTags, char *buffer, size_t bufferSize);
+  char *(*start)(void);
   void (*stop)(void);
 
   void (*begin_section)(uint64_t tag, const char *name, size_t numArgs, systrace_arg_t *args);

React/Profiler/RCTProfile.m

@@ -455,9 +455,7 @@ void RCTProfileInit(RCTBridge *bridge)
   OSAtomicOr32Barrier(1, &RCTProfileProfiling);
 
   if (callbacks != NULL) {
-    size_t buffer_size = 1 << 22;
-    systrace_buffer = calloc(1, buffer_size);
-    callbacks->start(~((uint64_t)0), systrace_buffer, buffer_size);
+    systrace_buffer = callbacks->start();
   } else {
     NSTimeInterval time = CACurrentMediaTime();
     dispatch_async(RCTProfileGetQueue(), ^{
@@ -514,9 +512,10 @@ void RCTProfileEnd(RCTBridge *bridge, void (^callback)(NSString *))
   RCTProfileUnhookModules(bridge);
 
   if (callbacks != NULL) {
-    callbacks->stop();
-
-    callback(@(systrace_buffer));
+    if (systrace_buffer) {
+      callbacks->stop();
+      callback(@(systrace_buffer));
+    }
   } else {
     dispatch_async(RCTProfileGetQueue(), ^{
       NSString *log = RCTJSONStringify(RCTProfileInfo, NULL);