From d15de921581ff500a48d1a463d33902bd499fad7 Mon Sep 17 00:00:00 2001
From: mwilsnd <53413200+mwilsnd@users.noreply.github.com>
Date: Fri, 19 Jul 2024 16:11:13 -0400
Subject: [PATCH] Take locks before signaling thread condition variables
 (#2636)

---
 src/mbgl/tile/tile_cache.cpp  | 2 ++
 src/mbgl/tile/tile_cache.hpp  | 3 +--
 src/mbgl/util/thread_pool.cpp | 2 ++
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/mbgl/tile/tile_cache.cpp b/src/mbgl/tile/tile_cache.cpp
index 8dc0bac35..2bbde03a8 100644
--- a/src/mbgl/tile/tile_cache.cpp
+++ b/src/mbgl/tile/tile_cache.cpp
@@ -53,6 +53,8 @@ void TileCache::deferredRelease(std::unique_ptr<Tile>&& tile) {
     // last one and the destruction actually occurs here on this thread.
     std::function<void()> func{[tile_{CaptureWrapper<Tile>{std::move(tile)}}, this]() mutable {
         tile_.item = {};
+
+        std::lock_guard<std::mutex> counterLock(deferredSignalLock);
         deferredDeletionsPending--;
         deferredSignal.notify_all();
     }};
diff --git a/src/mbgl/tile/tile_cache.hpp b/src/mbgl/tile/tile_cache.hpp
index 72d430db3..db9f8658c 100644
--- a/src/mbgl/tile/tile_cache.hpp
+++ b/src/mbgl/tile/tile_cache.hpp
@@ -50,10 +50,9 @@ private:
     std::map<OverscaledTileID, std::unique_ptr<Tile>> tiles;
     std::list<OverscaledTileID> orderedKeys;
     TaggedScheduler threadPool;
-    std::atomic<size_t> deferredDeletionsPending{0};
+    size_t deferredDeletionsPending{0};
     std::mutex deferredSignalLock;
     std::condition_variable deferredSignal;
-
     size_t size;
 };
 
diff --git a/src/mbgl/util/thread_pool.cpp b/src/mbgl/util/thread_pool.cpp
index af3f2e6a3..a2e4cc09d 100644
--- a/src/mbgl/util/thread_pool.cpp
+++ b/src/mbgl/util/thread_pool.cpp
@@ -130,6 +130,8 @@ void ThreadedSchedulerBase::schedule(const util::SimpleIdentity tag, std::functi
         taskCount++;
     }
 
+    // Take the worker lock before notifying to prevent threads from waiting while we try to wake them
+    std::lock_guard<std::mutex> workerLock(workerMutex);
     cvAvailable.notify_one();
 }