From 3bb4e2424dc4424edc30cddb384817bcab078438 Mon Sep 17 00:00:00 2001
From: Geoff Lang <geofflang@chromium.org>
Date: Wed, 01 Apr 2026 15:54:06 -0400
Subject: [PATCH] Metal: Store LibraryCacheEntry in a shared_ptr

This ensures that if an entry is removed from the cache while it is
compiling, it is not deleted until it is fully unreferenced.

If there were > kMaxCachedLibraries simultaneous compile requests, it
was possible that the cache gets trimmed while threads are compiling and
we can end up writing to removed cache entries.

Bug: chromium:497724490
Change-Id: Iba4281d5d12c6882de51fc1bf88d60157ffc7fb6
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/7722080
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: dan sinclair <dsinclair@chromium.org>
---

diff --git a/src/libANGLE/renderer/metal/mtl_library_cache.h b/src/libANGLE/renderer/metal/mtl_library_cache.h
index d936e6a..93dfc15 100644
--- a/src/libANGLE/renderer/metal/mtl_library_cache.h
+++ b/src/libANGLE/renderer/metal/mtl_library_cache.h
@@ -77,7 +77,7 @@
         std::mutex lock;
     };
 
-    LibraryCacheEntry &getCacheEntry(LibraryKey &&key);
+    std::shared_ptr<LibraryCacheEntry> getCacheEntry(LibraryKey &&key);
 
     static constexpr unsigned int kMaxCachedLibraries = 128;
 
@@ -87,7 +87,8 @@
     // Lock for searching and adding new entries to the cache
     std::mutex mCacheLock;
 
-    using CacheMap = angle::base::HashingMRUCache<LibraryKey, LibraryCacheEntry, LibraryKeyHasher>;
+    using CacheMap = angle::base::
+        HashingMRUCache<LibraryKey, std::shared_ptr<LibraryCacheEntry>, LibraryKeyHasher>;
     CacheMap mCache;
 };
 
diff --git a/src/libANGLE/renderer/metal/mtl_library_cache.mm b/src/libANGLE/renderer/metal/mtl_library_cache.mm
index 5fb63ea..27512a1 100644
--- a/src/libANGLE/renderer/metal/mtl_library_cache.mm
+++ b/src/libANGLE/renderer/metal/mtl_library_cache.mm
@@ -36,15 +36,15 @@
                                                  bool usesInvariance)
 {
     ASSERT(source != nullptr);
-    LibraryCache::LibraryCacheEntry &entry =
+    std::shared_ptr<LibraryCache::LibraryCacheEntry> entry =
         getCacheEntry(LibraryKey(source, macros, disableFastMath, usesInvariance));
 
     // Try to lock the entry and return the library if it exists. If we can't lock then it means
     // another thread is currently compiling.
-    std::unique_lock<std::mutex> entryLockGuard(entry.lock, std::try_to_lock);
+    std::unique_lock<std::mutex> entryLockGuard(entry->lock, std::try_to_lock);
     if (entryLockGuard)
     {
-        return entry.library;
+        return entry->library;
     }
     else
     {
@@ -69,23 +69,23 @@
     }
 
     ASSERT(source != nullptr);
-    LibraryCache::LibraryCacheEntry &entry =
+    std::shared_ptr<LibraryCache::LibraryCacheEntry> entry =
         getCacheEntry(LibraryKey(source, macros, disableFastMath, usesInvariance));
 
     // Lock this cache entry while compiling the shader. This causes other threads calling this
     // function to wait and not duplicate the compilation.
-    std::lock_guard<std::mutex> entryLockGuard(entry.lock);
-    if (entry.library)
+    std::lock_guard<std::mutex> entryLockGuard(entry->lock);
+    if (entry->library)
     {
-        return entry.library;
+        return entry->library;
     }
 
-    entry.library = CreateShaderLibrary(metalDevice, *source, macros, disableFastMath,
-                                        usesInvariance, errorOut);
-    return entry.library;
+    entry->library = CreateShaderLibrary(metalDevice, *source, macros, disableFastMath,
+                                         usesInvariance, errorOut);
+    return entry->library;
 }
 
-LibraryCache::LibraryCacheEntry &LibraryCache::getCacheEntry(LibraryKey &&key)
+std::shared_ptr<LibraryCache::LibraryCacheEntry> LibraryCache::getCacheEntry(LibraryKey &&key)
 {
     // Lock while searching or adding new items to the cache.
     std::lock_guard<std::mutex> cacheLockGuard(mCacheLock);
@@ -98,7 +98,7 @@
 
     angle::TrimCache(kMaxCachedLibraries, kGCLimit, "metal library", &mCache);
 
-    iter = mCache.Put(std::move(key), LibraryCacheEntry());
+    iter = mCache.Put(std::move(key), std::make_shared<LibraryCacheEntry>());
     return iter->second;
 }