[execution][heap] Make Isolate::is_profiling relaxed atomic

Concurrent allocation uses Isolate::is_profiling() to determine
whether logging is on. This races with the main thread when the
value in is_profiling is switched on/off by the cpu profiler.

Fix this by making is_profiling relaxed atomic. The profiler doesn't
turn off logging for correctness reasons, so it is fine when background
threads may read an old value and continue logging a bit longer. It is
also okay when background threads start logging again a bit longer when
profiling is stopped.

Bug: v8:10315
Change-Id: Id52d06f7a8239e10dfa63da38e761b2c00a2da4b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2404779
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69882}

src/execution/isolate.h

@@ -5,6 +5,7 @@
 #ifndef V8_EXECUTION_ISOLATE_H_
 #define V8_EXECUTION_ISOLATE_H_
 
+#include <atomic>
 #include <cstddef>
 #include <functional>
 #include <memory>
@@ -432,8 +433,6 @@ using DebugObjectCache = std::vector<Handle<HeapObject>>;
   V(int, code_and_metadata_size, 0)                                            \
   V(int, bytecode_and_metadata_size, 0)                                        \
   V(int, external_script_source_size, 0)                                       \
-  /* true if being profiled. Causes collection of extra compile info. */       \
-  V(bool, is_profiling, false)                                                 \
   /* Number of CPU profilers running on the isolate. */                        \
   V(size_t, num_cpu_profilers, 0)                                              \
   /* true if a trace is being formatted through Error.prepareStackTrace. */    \
@@ -1073,7 +1072,16 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
 
   Debug* debug() { return debug_; }
 
-  bool* is_profiling_address() { return &is_profiling_; }
+  void* is_profiling_address() { return &is_profiling_; }
+
+  bool is_profiling() const {
+    return is_profiling_.load(std::memory_order_relaxed);
+  }
+
+  void set_is_profiling(bool enabled) {
+    is_profiling_.store(enabled, std::memory_order_relaxed);
+  }
+
   CodeEventDispatcher* code_event_dispatcher() const {
     return code_event_dispatcher_.get();
   }
@@ -1732,6 +1740,9 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
 
 #endif  // V8_INTL_SUPPORT
 
+  // true if being profiled. Causes collection of extra compile info.
+  std::atomic<bool> is_profiling_{false};
+
   // Whether the isolate has been created for snapshotting.
   bool serializer_enabled_ = false;