[llvm-branch-commits] [lld] r322648 - Merging r322264:

[Hans Wennborg via llvm-branch-commits]

Author: hans
Date: Wed Jan 17 05:14:51 2018
New Revision: 322648

URL: http://llvm.org/viewvc/llvm-project?rev=322648&view=rev
Log:
Merging r322264:
------------------------------------------------------------------------
r322264 | dim | 2018-01-11 00:03:22 -0800 (Thu, 11 Jan 2018) | 17 lines

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

------------------------------------------------------------------------

Modified:
    lld/branches/release_60/   (props changed)
    lld/branches/release_60/ELF/SyntheticSections.cpp

Propchange: lld/branches/release_60/
------------------------------------------------------------------------------
--- svn:mergeinfo (original)
+++ svn:mergeinfo Wed Jan 17 05:14:51 2018
@@ -1 +1 @@
-/lld/trunk:321983,321986,322041,322259
+/lld/trunk:321983,321986,322041,322259,322264

Modified: lld/branches/release_60/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/branches/release_60/ELF/SyntheticSections.cpp?rev=322648&r1=322647&r2=322648&view=diff
==============================================================================
--- lld/branches/release_60/ELF/SyntheticSections.cpp (original)
+++ lld/branches/release_60/ELF/SyntheticSections.cpp Wed Jan 17 05:14:51 2018
@@ -2438,10 +2438,8 @@ void MergeNoTailSection::finalizeContent
   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));
       }
     }