ghc/includes/SMP.h

   1 /* ----------------------------------------------------------------------------
   2  * $Id: SMP.h,v 1.4 2002/02/04 20:10:47 sof Exp $
   3  *
   4  * (c) The GHC Team, 1999
   5  *
   6  * Macros for SMP support
   7  *
   8  * -------------------------------------------------------------------------- */
   9
  10 #ifndef SMP_H
  11 #define SMP_H
  12
  13 /* SMP is currently not compatible with the following options:
  14  *
  15  *      INTERPRETER
  16  *      PROFILING
  17  *      TICKY_TICKY
  18  *      and unregisterised builds.
  19  */
  20
  21 #if defined(SMP)
  22
  23 #if  defined(PROFILING)  || defined(TICKY_TICKY)
  24 #error Build options incompatible with SMP.
  25 #endif
  26
  27 /*
  28  * CMPXCHG - this instruction is the standard "test & set".  We use it
  29  * for locking closures in the thunk and blackhole entry code.  If the
  30  * closure is already locked, or has an unexpected info pointer
  31  * (because another thread is altering it in parallel), we just jump
  32  * to the new entry point.
  33  */
  34 #if defined(i386_TARGET_ARCH) && defined(TABLES_NEXT_TO_CODE)
  35 #define CMPXCHG(p, cmp, new)                    \
  36   __asm__ __volatile__ (                        \
  37           "lock ; cmpxchg %1, %0\n"             \
  38           "\tje 1f\n"                           \
  39           "\tjmp *%%eax\n"                      \
  40           "\t1:\n"                              \
  41           : /* no outputs */                    \
  42           : "m" (p), "r" (new), "r" (cmp)       \
  43           )
  44
  45 /*
  46  * XCHG - the atomic exchange instruction.  Used for locking closures
  47  * during updates (see LOCK_CLOSURE below) and the MVar primops.
  48  */
  49 #define XCHG(reg, obj)                          \
  50   __asm__ __volatile__ (                        \
  51           "xchgl %1,%0"                         \
  52           :"+r" (reg), "+m" (obj)               \
  53           : /* no input-only operands */        \
  54           )
  55
  56 #else
  57 #error SMP macros not defined for this architecture
  58 #endif
  59
  60 /*
  61  * LOCK_CLOSURE locks the specified closure, busy waiting for any
  62  * existing locks to be cleared.
  63  */
  64 #define LOCK_CLOSURE(c)                                 \
  65   ({                                                    \
  66     const StgInfoTable *__info;                         \
  67     __info = &stg_WHITEHOLE_info;                       \
  68     do {                                                \
  69       XCHG(__info,((StgClosure *)(c))->header.info);    \
  70     } while (__info == &stg_WHITEHOLE_info);            \
  71     __info;                                             \
  72   })
  73
  74 #define LOCK_THUNK(__info)                              \
  75   CMPXCHG(R1.cl->header.info, __info, &stg_WHITEHOLE_info);
  76
  77 #else /* !SMP */
  78
  79 #define LOCK_CLOSURE(c)     /* nothing */
  80 #define LOCK_THUNK(__info)  /* nothing */
  81
  82 #endif /* SMP */
  83
  84 #endif /* SMP_H */