ghc/includes/SMP.h

   1 /* ----------------------------------------------------------------------------
   2  *
   3  * (c) The GHC Team, 1999
   4  *
   5  * Macros for SMP support
   6  *
   7  * -------------------------------------------------------------------------- */
   8
   9 #ifndef SMP_H
  10 #define SMP_H
  11
  12 /* SMP is currently not compatible with the following options:
  13  *
  14  *      INTERPRETER
  15  *      PROFILING
  16  *      TICKY_TICKY
  17  *      and unregisterised builds.
  18  */
  19
  20 #if defined(SMP)
  21
  22 #if  defined(PROFILING)  || defined(TICKY_TICKY)
  23 #error Build options incompatible with SMP.
  24 #endif
  25
  26 /*
  27  * CMPXCHG - this instruction is the standard "test & set".  We use it
  28  * for locking closures in the thunk and blackhole entry code.  If the
  29  * closure is already locked, or has an unexpected info pointer
  30  * (because another thread is altering it in parallel), we just jump
  31  * to the new entry point.
  32  */
  33 #if defined(i386_HOST_ARCH) && defined(TABLES_NEXT_TO_CODE)
  34 #define CMPXCHG(p, cmp, new)                    \
  35   __asm__ __volatile__ (                        \
  36           "lock ; cmpxchg %1, %0\n"             \
  37           "\tje 1f\n"                           \
  38           "\tjmp *%%eax\n"                      \
  39           "\t1:\n"                              \
  40           : /* no outputs */                    \
  41           : "m" (p), "r" (new), "r" (cmp)       \
  42           )
  43
  44 /*
  45  * XCHG - the atomic exchange instruction.  Used for locking closures
  46  * during updates (see LOCK_CLOSURE below) and the MVar primops.
  47  */
  48 #define XCHG(reg, obj)                          \
  49   __asm__ __volatile__ (                        \
  50           "xchgl %1,%0"                         \
  51           :"+r" (reg), "+m" (obj)               \
  52           : /* no input-only operands */        \
  53           )
  54
  55 #else
  56 #error SMP macros not defined for this architecture
  57 #endif
  58
  59 /*
  60  * LOCK_CLOSURE locks the specified closure, busy waiting for any
  61  * existing locks to be cleared.
  62  */
  63 #define LOCK_CLOSURE(c)                                 \
  64   ({                                                    \
  65     const StgInfoTable *__info;                         \
  66     __info = &stg_WHITEHOLE_info;                       \
  67     do {                                                \
  68       XCHG(__info,((StgClosure *)(c))->header.info);    \
  69     } while (__info == &stg_WHITEHOLE_info);            \
  70     __info;                                             \
  71   })
  72
  73 #define LOCK_THUNK(__info)                              \
  74   CMPXCHG(R1.cl->header.info, __info, &stg_WHITEHOLE_info);
  75
  76 #else /* !SMP */
  77
  78 #define LOCK_CLOSURE(c)     /* nothing */
  79 #define LOCK_THUNK(__info)  /* nothing */
  80
  81 #endif /* SMP */
  82
  83 #endif /* SMP_H */