#15449: Nondeterministic Failure on aarch64 with -jn, n > 1 -------------------------------------+------------------------------------- Reporter: tmobile | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: Operating System: Linux | Architecture: aarch64 Type of failure: Compile-time | Test Case: crash or panic | Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by trommler): At some point Aarch64 was switched over from the C backend to the LLVM backend. A quick glance at the LLVM backend showed the following suspicious code in `compiler/llvmGen/LlvmCodeGen`: {{{ genCall (PrimTarget (MO_AtomicRead _)) [dst] [addr] = runStmtsDecls $ do dstV <- getCmmRegW (CmmLocal dst) v1 <- genLoadW True addr (localRegType dst) statement $ Store v1 dstV }}} A full barrier is required here but no barrier at all is present. Remark: I have similar issues on PowerPC and putting the appropriate barrier into atomic reads improved the situation (fewer crashes of the sort described above) but did not solve the issue completely. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15449#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler