From 2c7f4de3e684d6dc9c10c503d1ca05765809b3c4 Mon Sep 17 00:00:00 2001
From: Francis Tsui <ftsui@google.com>
Date: Wed, 1 Oct 2025 15:23:46 -0700
Subject: [PATCH] Make TimerImpl thread-safe.

PiperOrigin-RevId: 813938502
---
 internal/platform/BUILD         | 17 +----------------
 internal/platform/timer_impl.cc | 18 ++++++++++++------
 internal/platform/timer_impl.h  |  5 ++++-
 3 files changed, 17 insertions(+), 23 deletions(-)

diff --git a/internal/platform/BUILD b/internal/platform/BUILD
index f84cbb0c..67d6a8cd 100644
--- a/internal/platform/BUILD
+++ b/internal/platform/BUILD
@@ -253,26 +253,11 @@ cc_library(
         "timer_impl.h",
     ],
     visibility = [
-        "//connections:__subpackages__",
-        "//internal/account:__subpackages__",
-        "//internal/auth:__subpackages__",
-        "//internal/auth/credential_store:__subpackages__",
-        "//internal/base:__subpackages__",
-        "//internal/crypto:__subpackages__",
-        "//internal/data:__subpackages__",
-        "//internal/interop:__pkg__",
-        "//internal/network:__subpackages__",
-        "//internal/platform:__subpackages__",
-        "//internal/preferences:__subpackages__",
-        "//internal/proto/analytics:__subpackages__",
-        "//internal/test:__subpackages__",
-        "//internal/weave:__subpackages__",
+        "//:__subpackages__",
         "//location/nearby/apps:__subpackages__",
         "//location/nearby/cpp:__subpackages__",
         "//location/nearby/sharing/sdk:__subpackages__",
         "//location/nearby/testing/nearby_native:__subpackages__",
-        "//presence:__subpackages__",
-        "//sharing:__subpackages__",
     ],
     deps = [
         ":base",
diff --git a/internal/platform/timer_impl.cc b/internal/platform/timer_impl.cc
index bd9c8159..20aaf455 100644
--- a/internal/platform/timer_impl.cc
+++ b/internal/platform/timer_impl.cc
@@ -17,6 +17,7 @@
 #include <utility>
 
 #include "absl/functional/any_invocable.h"
+#include "absl/synchronization/mutex.h"
 #include "internal/platform/implementation/platform.h"
 #include "internal/platform/logging.h"
 
@@ -24,17 +25,18 @@ namespace nearby {
 
 bool TimerImpl::Start(int delay, int period,
                       absl::AnyInvocable<void()> callback) {
-  if (internal_timer_ != nullptr) {
-    LOG(INFO) << "The timer is already running.";
-    return false;
-  }
-
   if (delay < 0) {
     delay = 0;
   }
   if (period < 0) {
     period = 0;
   }
+  absl::MutexLock lock(&mutex_);
+  if (internal_timer_ != nullptr) {
+    LOG(INFO) << "The timer is already running.";
+    return false;
+  }
+
   internal_timer_ = api::ImplementationPlatform::CreateTimer();
   if (!internal_timer_->Create(delay, period, std::move(callback))) {
     LOG(INFO) << "Failed to create timer.";
@@ -45,6 +47,7 @@ bool TimerImpl::Start(int delay, int period,
 }
 
 void TimerImpl::Stop() {
+  absl::MutexLock lock(&mutex_);
   if (internal_timer_ == nullptr) {
     return;
   }
@@ -53,6 +56,9 @@ void TimerImpl::Stop() {
   internal_timer_ = nullptr;
 }
 
-bool TimerImpl::IsRunning() { return (internal_timer_ != nullptr); }
+bool TimerImpl::IsRunning() {
+  absl::MutexLock lock(&mutex_);
+  return (internal_timer_ != nullptr);
+}
 
 }  // namespace nearby
diff --git a/internal/platform/timer_impl.h b/internal/platform/timer_impl.h
index a918fcd8..06eb45f9 100644
--- a/internal/platform/timer_impl.h
+++ b/internal/platform/timer_impl.h
@@ -17,7 +17,9 @@
 
 #include <memory>
 
+#include "absl/base/thread_annotations.h"
 #include "absl/functional/any_invocable.h"
+#include "absl/synchronization/mutex.h"
 #include "internal/platform/implementation/timer.h"
 #include "internal/platform/timer.h"
 
@@ -32,7 +34,8 @@ class TimerImpl : public Timer {
   bool IsRunning() override;
 
  private:
-  std::unique_ptr<api::Timer> internal_timer_ = nullptr;
+  absl::Mutex mutex_;
+  std::unique_ptr<api::Timer> internal_timer_ ABSL_GUARDED_BY(mutex_) = nullptr;
 };
 
 }  // namespace nearby