[heap] Avoid ParkedMutexGuard during allocation

Since main thread allocation does not start incremental marking anymore
while holding allocation_mutex_, background allocation does not need
ParkedMutexGuard anymore to avoid deadlocks.

This also means background thread allocation isn't paused anymore to
perform a GC, which already resulted in subtle bugs (e.g. in
ExpandBackground with incremental marking). We also do not
stop-the-world anymore while holding allocation_mutex_.

Bug: v8:10315
Change-Id: Iadf00bc26434c765722b82a10497ab06151f15cc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2289771Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68754}

src/heap/paged-spaces.cc

@@ -347,7 +347,7 @@ Page* PagedSpace::Expand() {
 Page* PagedSpace::ExpandBackground(LocalHeap* local_heap) {
   Page* page = AllocatePage();
   if (page == nullptr) return nullptr;
-  ParkedMutexGuard lock(local_heap, &allocation_mutex_);
+  base::MutexGuard lock(&allocation_mutex_);
   AddPage(page);
   Free(page->area_start(), page->area_size(),
        SpaceAccountingMode::kSpaceAccounted);
@@ -580,7 +580,7 @@ PagedSpace::SlowGetLinearAllocationAreaBackground(LocalHeap* local_heap,
     // First try to refill the free-list, concurrent sweeper threads
     // may have freed some objects in the meantime.
     {
-      ParkedMutexGuard lock(local_heap, &allocation_mutex_);
+      base::MutexGuard lock(&allocation_mutex_);
       RefillFreeList();
     }
 
@@ -599,7 +599,7 @@ PagedSpace::SlowGetLinearAllocationAreaBackground(LocalHeap* local_heap,
         invalidated_slots_in_free_space);
 
     {
-      ParkedMutexGuard lock(local_heap, &allocation_mutex_);
+      base::MutexGuard lock(&allocation_mutex_);
       RefillFreeList();
     }
 
@@ -631,7 +631,7 @@ PagedSpace::TryAllocationFromFreeListBackground(LocalHeap* local_heap,
                                                 size_t max_size_in_bytes,
                                                 AllocationAlignment alignment,
                                                 AllocationOrigin origin) {
-  ParkedMutexGuard lock(local_heap, &allocation_mutex_);
+  base::MutexGuard lock(&allocation_mutex_);
   DCHECK_LE(min_size_in_bytes, max_size_in_bytes);
   DCHECK_EQ(identity(), OLD_SPACE);