diff --git a/services/surfaceflinger/Scheduler/OneShotTimer.cpp b/services/surfaceflinger/Scheduler/OneShotTimer.cpp
index a90d05e..2783800 100644
--- a/services/surfaceflinger/Scheduler/OneShotTimer.cpp
+++ b/services/surfaceflinger/Scheduler/OneShotTimer.cpp
@@ -20,6 +20,21 @@
 #include <sstream>
 #include <thread>
 
+namespace {
+using namespace std::chrono_literals;
+
+constexpr int64_t kNsToSeconds = std::chrono::duration_cast<std::chrono::nanoseconds>(1s).count();
+
+// The syscall interface uses a pair of integers for the timestamp. The first
+// (tv_sec) is the whole count of seconds. The second (tv_nsec) is the
+// nanosecond part of the count. This function takes care of translation.
+void calculateTimeoutTime(std::chrono::nanoseconds timestamp, timespec* spec) {
+    clock_gettime(CLOCK_MONOTONIC, spec);
+    spec->tv_sec += static_cast<__kernel_time_t>(timestamp.count() / kNsToSeconds);
+    spec->tv_nsec += timestamp.count() % kNsToSeconds;
+}
+} // namespace
+
 namespace android {
 namespace scheduler {
 
@@ -32,81 +47,95 @@
 }
 
 void OneShotTimer::start() {
-    {
-        std::lock_guard<std::mutex> lock(mMutex);
-        mState = TimerState::RESET;
+    sem_init(&mSemaphore, 0, 0);
+
+    if (!mThread.joinable()) {
+        // Only create thread if it has not been created.
+        mThread = std::thread(&OneShotTimer::loop, this);
     }
-    mThread = std::thread(&OneShotTimer::loop, this);
 }
 
 void OneShotTimer::stop() {
-    {
-        std::lock_guard<std::mutex> lock(mMutex);
-        mState = TimerState::STOPPED;
-    }
-    mCondition.notify_all();
+    mStopTriggered = true;
+    sem_post(&mSemaphore);
+
     if (mThread.joinable()) {
         mThread.join();
+        sem_destroy(&mSemaphore);
     }
 }
 
 void OneShotTimer::loop() {
+    TimerState state = TimerState::RESET;
     while (true) {
         bool triggerReset = false;
         bool triggerTimeout = false;
-        {
-            std::lock_guard<std::mutex> lock(mMutex);
-            if (mState == TimerState::STOPPED) {
-                break;
-            }
 
-            if (mState == TimerState::IDLE) {
-                mCondition.wait(mMutex);
-                continue;
-            }
-
-            if (mState == TimerState::RESET) {
-                triggerReset = true;
-            }
+        state = checkForResetAndStop(state);
+        if (state == TimerState::STOPPED) {
+            break;
         }
+
+        if (state == TimerState::IDLE) {
+            sem_wait(&mSemaphore);
+            continue;
+        }
+
+        if (state == TimerState::RESET) {
+            triggerReset = true;
+        }
+
         if (triggerReset && mResetCallback) {
             mResetCallback();
         }
 
-        { // lock the mutex again. someone might have called stop meanwhile
-            std::lock_guard<std::mutex> lock(mMutex);
-            if (mState == TimerState::STOPPED) {
-                break;
-            }
+        state = checkForResetAndStop(state);
+        if (state == TimerState::STOPPED) {
+            break;
+        }
 
-            auto triggerTime = std::chrono::steady_clock::now() + mInterval;
-            mState = TimerState::WAITING;
-            while (mState == TimerState::WAITING) {
-                constexpr auto zero = std::chrono::steady_clock::duration::zero();
-                auto waitTime = triggerTime - std::chrono::steady_clock::now();
-                if (waitTime > zero) mCondition.wait_for(mMutex, waitTime);
-                if (mState == TimerState::RESET) {
-                    triggerTime = std::chrono::steady_clock::now() + mInterval;
-                    mState = TimerState::WAITING;
-                } else if (mState == TimerState::WAITING &&
-                           (triggerTime - std::chrono::steady_clock::now()) <= zero) {
-                    triggerTimeout = true;
-                    mState = TimerState::IDLE;
-                }
+        auto triggerTime = std::chrono::steady_clock::now() + mInterval;
+        state = TimerState::WAITING;
+        while (state == TimerState::WAITING) {
+            constexpr auto zero = std::chrono::steady_clock::duration::zero();
+            // Wait for mInterval time for semaphore signal.
+            struct timespec ts;
+            calculateTimeoutTime(std::chrono::nanoseconds(mInterval), &ts);
+            sem_clockwait(&mSemaphore, CLOCK_MONOTONIC, &ts);
+
+            state = checkForResetAndStop(state);
+            if (state == TimerState::RESET) {
+                triggerTime = std::chrono::steady_clock::now() + mInterval;
+                state = TimerState::WAITING;
+            } else if (state == TimerState::WAITING &&
+                       (triggerTime - std::chrono::steady_clock::now()) <= zero) {
+                triggerTimeout = true;
+                state = TimerState::IDLE;
             }
         }
+
         if (triggerTimeout && mTimeoutCallback) {
             mTimeoutCallback();
         }
     }
 }
 
-void OneShotTimer::reset() {
-    {
-        std::lock_guard<std::mutex> lock(mMutex);
-        mState = TimerState::RESET;
+OneShotTimer::TimerState OneShotTimer::checkForResetAndStop(TimerState state) {
+    // Stop takes precedence of the reset.
+    if (mStopTriggered.exchange(false)) {
+        return TimerState::STOPPED;
     }
-    mCondition.notify_all();
+    // If the state was stopped, the thread was joined, and we cannot reset
+    // the timer anymore.
+    if (state != TimerState::STOPPED && mResetTriggered.exchange(false)) {
+        return TimerState::RESET;
+    }
+    return state;
+}
+
+void OneShotTimer::reset() {
+    mResetTriggered = true;
+    sem_post(&mSemaphore);
 }
 
 std::string OneShotTimer::dump() const {
diff --git a/services/surfaceflinger/Scheduler/OneShotTimer.h b/services/surfaceflinger/Scheduler/OneShotTimer.h
index b005754..8bbd4f5 100644
--- a/services/surfaceflinger/Scheduler/OneShotTimer.h
+++ b/services/surfaceflinger/Scheduler/OneShotTimer.h
@@ -16,6 +16,7 @@
 
 #pragma once
 
+#include <semaphore.h>
 #include <chrono>
 #include <condition_variable>
 #include <thread>
@@ -70,17 +71,15 @@
     // Function that loops until the condition for stopping is met.
     void loop();
 
+    // Checks whether mResetTriggered and mStopTriggered were set and updates
+    // mState if so.
+    TimerState checkForResetAndStop(TimerState state);
+
     // Thread waiting for timer to expire.
     std::thread mThread;
 
-    // Condition used to notify mThread.
-    std::condition_variable_any mCondition;
-
-    // Lock used for synchronizing the waiting thread with the application thread.
-    std::mutex mMutex;
-
-    // Current timer state
-    TimerState mState GUARDED_BY(mMutex) = TimerState::RESET;
+    // Semaphore to keep mThread synchronized.
+    sem_t mSemaphore;
 
     // Interval after which timer expires.
     const Interval mInterval;
@@ -90,6 +89,12 @@
 
     // Callback that happens when timer expires.
     const TimeoutCallback mTimeoutCallback;
+
+    // After removing lock guarding mState, the state can be now accessed at
+    // any time. Keep a bool if the reset or stop were requested, and occasionally
+    // check in the main loop if they were.
+    std::atomic<bool> mResetTriggered = false;
+    std::atomic<bool> mStopTriggered = false;
 };
 
 } // namespace scheduler