[GHC] #12070: SMP primitives broken on power(pc)

#12070: SMP primitives broken on power(pc) -------------------------------------+------------------------------------- Reporter: hvr | Owner: trommler Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Runtime | Version: 8.0.1-rc4 System | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I originally noticed this when working on the AIX port (32-bit powerpc), and recently saw this also on Linux/powerpc64, which lead to talking to Peter Trommler who already had a suspicion: Here's for example the CAS definition (in ``): {{{#!c StgWord cas(StgVolatilePtr p, StgWord o, StgWord n) { StgWord result; __asm__ __volatile__ ( "1: ldarx %0, 0, %3\n" " cmpd %0, %1\n" " bne 2f\n" " stdcx. %2, 0, %3\n" " bne- 1b\n" "2:" :"=&r" (result) :"r" (o), "r" (n), "r" (p) :"cc", "memory" ); return result; }}} The important detail is the lack any barrier instructions, such as `isync` at the end. This results in infrequent heap-corruptions which in turn result in all sorts of infrequent and hard to track down runtime-crashes (including in `ghc -j`). Peter has already a patch in the works which simply replaces the atomic powerpc primitives with `__sync_*` intrinsics which turn out to be more portable than inline-asm. I've been testing the patch already and it seems to have made all issues I experienced so far disappear, as well as fixing the `concprog01` test which was also failing infrequently. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12070 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler