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Pull in r322264 from upstream lld trunk (by me):

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Fix thread race between SectionPiece's OutputOff and Live members

  Summary:
  As reported in bug 35788, rL316280 reintroduces a race between two
  members of SectionPiece, which share the same 64 bit memory location.

  To fix the race, check the hash before checking the Live member, as
  suggested by Rafael.

  Reviewers: ruiu, rafael

  Reviewed By: ruiu

  Subscribers: smeenai, emaste, llvm-commits

  Differential Revision: https://reviews.llvm.org/D41884
This commit is contained in:
dim 2018-01-12 18:16:51 +00:00
parent 33895baa09
commit b701edc6bb
1 changed files with 1 additions and 3 deletions
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4
contrib/llvm/tools/lld/ELF/SyntheticSections.cpp
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@ -2435,10 +2435,8 @@ void MergeNoTailSection::finalizeContents() {
parallelForEachN(0, Concurrency, [&](size_t ThreadId) {
for (MergeInputSection *Sec : Sections) {
for (size_t I = 0, E = Sec->Pieces.size(); I != E; ++I) {
if (!Sec->Pieces[I].Live)
continue;
size_t ShardId = getShardId(Sec->Pieces[I].Hash);
if ((ShardId & (Concurrency - 1)) == ThreadId)
if ((ShardId & (Concurrency - 1)) == ThreadId && Sec->Pieces[I].Live)
Sec->Pieces[I].OutputOff = Shards[ShardId].add(Sec->getData(I));
}
}