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/* ----------------------------------------------------------------------------
* $Id: SMP.h,v 1.5 2005/01/28 12:55:52 simonmar Exp $
*
* (c) The GHC Team, 1999
*
* Macros for SMP support
*
* -------------------------------------------------------------------------- */
#ifndef SMP_H
#define SMP_H
/* SMP is currently not compatible with the following options:
*
* INTERPRETER
* PROFILING
* TICKY_TICKY
* and unregisterised builds.
*/
#if defined(SMP)
#if defined(PROFILING) || defined(TICKY_TICKY)
#error Build options incompatible with SMP.
#endif
/*
* CMPXCHG - this instruction is the standard "test & set". We use it
* for locking closures in the thunk and blackhole entry code. If the
* closure is already locked, or has an unexpected info pointer
* (because another thread is altering it in parallel), we just jump
* to the new entry point.
*/
#if defined(i386_HOST_ARCH) && defined(TABLES_NEXT_TO_CODE)
#define CMPXCHG(p, cmp, new) \
__asm__ __volatile__ ( \
"lock ; cmpxchg %1, %0\n" \
"\tje 1f\n" \
"\tjmp *%%eax\n" \
"\t1:\n" \
: /* no outputs */ \
: "m" (p), "r" (new), "r" (cmp) \
)
/*
* XCHG - the atomic exchange instruction. Used for locking closures
* during updates (see LOCK_CLOSURE below) and the MVar primops.
*/
#define XCHG(reg, obj) \
__asm__ __volatile__ ( \
"xchgl %1,%0" \
:"+r" (reg), "+m" (obj) \
: /* no input-only operands */ \
)
#else
#error SMP macros not defined for this architecture
#endif
/*
* LOCK_CLOSURE locks the specified closure, busy waiting for any
* existing locks to be cleared.
*/
#define LOCK_CLOSURE(c) \
({ \
const StgInfoTable *__info; \
__info = &stg_WHITEHOLE_info; \
do { \
XCHG(__info,((StgClosure *)(c))->header.info); \
} while (__info == &stg_WHITEHOLE_info); \
__info; \
})
#define LOCK_THUNK(__info) \
CMPXCHG(R1.cl->header.info, __info, &stg_WHITEHOLE_info);
#else /* !SMP */
#define LOCK_CLOSURE(c) /* nothing */
#define LOCK_THUNK(__info) /* nothing */
#endif /* SMP */
#endif /* SMP_H */
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