[compiler-rt] b3e4283 - [scudo] Fix insufficient blocks when pushing BatchClass blocks

[Chia-hung Duan via llvm-commits]

Author: Chia-hung Duan
Date: 2023-06-26T22:37:58Z
New Revision: b3e42830aba036e8ef1a37734872dba73ee750e7

URL: https://github.com/llvm/llvm-project/commit/b3e42830aba036e8ef1a37734872dba73ee750e7
DIFF: https://github.com/llvm/llvm-project/commit/b3e42830aba036e8ef1a37734872dba73ee750e7.diff

LOG: [scudo] Fix insufficient blocks when pushing BatchClass blocks

`populateFreeListAndPopBatch` may return batch with single block. Merge
it with the reported free blocks and enqueue them together.

Reviewed By: cferris, fabio-d

Differential Revision: https://reviews.llvm.org/D153787

Added: 
    

Modified: 
    compiler-rt/lib/scudo/standalone/primary64.h

Removed: 
    


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diff  --git a/compiler-rt/lib/scudo/standalone/primary64.h b/compiler-rt/lib/scudo/standalone/primary64.h
index 43a977b19628f..ab75f19d8a18d 100644
--- a/compiler-rt/lib/scudo/standalone/primary64.h
+++ b/compiler-rt/lib/scudo/standalone/primary64.h
@@ -224,9 +224,24 @@ template <typename Config> class SizeClassAllocator64 {
                                     B == nullptr;
           if (UNLIKELY(!NeedToRefill)) {
             if (UNLIKELY(B)) {
+              // Even though we always populate the blocks with the number which
+              // is multiple of TransferBatch::getMaxCached() , the top
+              // `TransferBatch` from the freelist may still have fewer elements
+              // than the size of TransferBatch::getMaxCached() because we
+              // always fill up the top `TransferBatch` first when it's not
+              // full.
+              // When this happens, simply push the block in `TransferBatch` and
+              // `Array` together.
+              if (UNLIKELY(B->getCount() == 1)) {
+                DCHECK_EQ(Size, 1U);
+                B->appendFromArray(Array, 1U);
+                Size = 0;
+              }
               pushBlocksImpl(C, SizeClassMap::BatchClassId, Region,
                              B->getRawArray(), B->getCount());
               CHECK(!Region->FreeListInfo.BlockList.empty());
+              if (Size == 0)
+                return;
             }
             pushBlocksImpl(C, SizeClassMap::BatchClassId, Region, Array, Size);
             return;