includes/SMPClosureOps.h

   1 /* ----------------------------------------------------------------------------
   2  *
   3  * (c) The GHC Team, 2005
   4  *
   5  * Macros for THREADED_RTS support
   6  *
   7  * -------------------------------------------------------------------------- */
   8
   9 #ifndef SMPCLOSUREOPS_H
  10 #define SMPCLOSUREOPS_H
  11
  12 #if defined(THREADED_RTS)
  13
  14 /* -----------------------------------------------------------------------------
  15  * Locking/unlocking closures
  16  *
  17  * This is used primarily in the implementation of MVars.
  18  * -------------------------------------------------------------------------- */
  19
  20 #define SPIN_COUNT 4000
  21
  22 #ifdef KEEP_LOCKCLOSURE
  23 // We want a callable copy of lockClosure() so that we can refer to it
  24 // from .cmm files compiled using the native codegen.
  25 extern StgInfoTable *lockClosure(StgClosure *p);
  26 INLINE_ME
  27 #else
  28 INLINE_HEADER
  29 #endif
  30 StgInfoTable *
  31 lockClosure(StgClosure *p)
  32 {
  33     StgWord info;
  34     do {
  35         nat i = 0;
  36         do {
  37             info = xchg((P_)(void *)&p->header.info, (W_)&stg_WHITEHOLE_info);
  38             if (info != (W_)&stg_WHITEHOLE_info) return (StgInfoTable *)info;
  39         } while (++i < SPIN_COUNT);
  40         yieldThread();
  41     } while (1);
  42 }
  43
  44 INLINE_HEADER void
  45 unlockClosure(StgClosure *p, const StgInfoTable *info)
  46 {
  47     // This is a strictly ordered write, so we need a write_barrier():
  48     write_barrier();
  49     p->header.info = info;
  50 }
  51
  52 #else /* !THREADED_RTS */
  53
  54 INLINE_HEADER StgInfoTable *
  55 lockClosure(StgClosure *p)
  56 { return (StgInfoTable *)p->header.info; }
  57
  58 INLINE_HEADER void
  59 unlockClosure(StgClosure *p STG_UNUSED, const StgInfoTable *info STG_UNUSED)
  60 { /* nothing */ }
  61
  62 #endif /* THREADED_RTS */
  63
  64 // Handy specialised versions of lockClosure()/unlockClosure()
  65 INLINE_HEADER void lockTSO(StgTSO *tso)
  66 { lockClosure((StgClosure *)tso); }
  67
  68 INLINE_HEADER void unlockTSO(StgTSO *tso)
  69 { unlockClosure((StgClosure*)tso, (const StgInfoTable *)&stg_TSO_info); }
  70
  71 #endif /* SMPCLOSUREOPS_H */