base/allocator: Convert a SpinLock to base::Lock.

The hooks' spinlock in PartitionAlloc is not performance-sensitive, and
is likely used as PartitionAlloc used not to rely on base/. Removing it
to reduce the use of custom locking (see the attached bug for
motivations).

Bug: 1061437
Change-Id: Id1d74ac9f108bdc462fd0d5586e89b0be056b67a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2102532
Commit-Queue: Benoit L <lizeb@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Chris Palmer <palmer@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750521}

base/allocator/partition_allocator/partition_alloc.cc

@@ -15,6 +15,7 @@
 #include "base/allocator/partition_allocator/spin_lock.h"
 #include "base/logging.h"
 #include "base/no_destructor.h"
+#include "base/synchronization/lock.h"
 
 namespace base {
 
@@ -62,9 +63,13 @@ subtle::SpinLock& GetLock() {
 }
 static bool g_initialized = false;
 
+Lock& GetHooksLock() {
+  static NoDestructor<Lock> lock;
+  return *lock;
+}
+
 OomFunction internal::PartitionRootBase::g_oom_handling_function = nullptr;
 std::atomic<bool> PartitionAllocHooks::hooks_enabled_(false);
-subtle::SpinLock PartitionAllocHooks::set_hooks_lock_;
 std::atomic<PartitionAllocHooks::AllocationObserverHook*>
     PartitionAllocHooks::allocation_observer_hook_(nullptr);
 std::atomic<PartitionAllocHooks::FreeObserverHook*>
@@ -78,7 +83,7 @@ std::atomic<PartitionAllocHooks::ReallocOverrideHook*>
 
 void PartitionAllocHooks::SetObserverHooks(AllocationObserverHook* alloc_hook,
                                            FreeObserverHook* free_hook) {
-  subtle::SpinLock::Guard guard(set_hooks_lock_);
+  AutoLock guard(GetHooksLock());
 
   // Chained hooks are not supported. Registering a non-null hook when a
   // non-null hook is already registered indicates somebody is trying to
@@ -95,7 +100,7 @@ void PartitionAllocHooks::SetObserverHooks(AllocationObserverHook* alloc_hook,
 void PartitionAllocHooks::SetOverrideHooks(AllocationOverrideHook* alloc_hook,
                                            FreeOverrideHook* free_hook,
                                            ReallocOverrideHook realloc_hook) {
-  subtle::SpinLock::Guard guard(set_hooks_lock_);
+  AutoLock guard(GetHooksLock());
 
   CHECK((!allocation_override_hook_ && !free_override_hook_ &&
          !realloc_override_hook_) ||

base/allocator/partition_allocator/partition_alloc.h

@@ -282,8 +282,6 @@ class BASE_EXPORT PartitionAllocHooks {
   static std::atomic<bool> hooks_enabled_;
 
   // Lock used to synchronize Set*Hooks calls.
-  static subtle::SpinLock set_hooks_lock_;
-
   static std::atomic<AllocationObserverHook*> allocation_observer_hook_;
   static std::atomic<FreeObserverHook*> free_observer_hook_;