b8546491fc
git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1315 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
101 lines
3.2 KiB
C
101 lines
3.2 KiB
C
/**********************************************************************
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The OPTYap Prolog system
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OPTYap extends the Yap Prolog system to support or-parallel tabling
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Copyright: R. Rocha and NCC - University of Porto, Portugal
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File: x86_locks.h
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version: $Id: x86_locks.h,v 1.3 2005-05-31 08:24:24 ricroc Exp $
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**********************************************************************/
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/* ----------------------------- **
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** Atomic lock for X86 **
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** ----------------------------- */
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#define swap(reg,adr) \
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({ \
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char _ret; \
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asm volatile ("xchgb %0,%1" \
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: "=q" (_ret), "=m" (*(adr)) /* Output %0,%1 */ \
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: "m" (*(adr)), "0" (reg)); /* Input (%2),%0 */ \
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_ret; \
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})
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#define TRY_LOCK(LOCK_VAR) (swap(1,(LOCK_VAR))==0)
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#define INIT_LOCK(LOCK_VAR) ((LOCK_VAR) = 0)
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#define LOCK(LOCK_VAR) do { \
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if (TRY_LOCK(&(LOCK_VAR))) break; \
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while (IS_LOCKED(LOCK_VAR)) continue; \
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} while (1)
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#define IS_LOCKED(LOCK_VAR) ((LOCK_VAR) != 0)
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#define IS_UNLOCKED(LOCK_VAR) ((LOCK_VAR) == 0)
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#define UNLOCK(LOCK_VAR) ((LOCK_VAR) = 0)
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/* This code has been copied from the sources of the Linux kernel */
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/*
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* On x86, we implement read-write locks as a 32-bit counter
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* with the high bit (sign) being the "contended" bit.
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*
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* The inline assembly is non-obvious. Think about it.
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*
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* Changed to use the same technique as rw semaphores. See
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* semaphore.h for details. -ben
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*/
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/* the spinlock helpers are in arch/i386/kernel/semaphore.S */
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typedef struct { unsigned long a[100]; } __dummy_lock_t;
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#define __dummy_lock(lock) (*(__dummy_lock_t *)(lock))
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typedef struct { volatile unsigned int lock; } rwlock_t;
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#define RW_LOCK_BIAS 0x01000000
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#define RW_LOCK_BIAS_STR "0x01000000"
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#define RW_LOCK_UNLOCKED RW_LOCK_BIAS
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#define __build_read_lock(rw, helper) \
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asm volatile("lock\n" \
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"subl $1,(%0)\n\t" \
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"js 2f\n" \
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"1:\n" \
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".section .text.lock,\"ax\"\n" \
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"2:\tcall __read_lock_failed\n\t" \
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"jmp 1b\n" \
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".previous" \
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::"a" (rw) : "memory")
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#define __build_write_lock(rw, helper) \
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asm volatile("lock\n"\
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"subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
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"jnz 2f\n" \
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"1:\n" \
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".section .text.lock,\"ax\"\n" \
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"2:\tcall __write_lock_failed\n\t" \
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"jmp 1b\n" \
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".previous" \
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::"a" (rw) : "memory")
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static inline void read_lock(rwlock_t *rw)
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{
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__build_read_lock(rw, "__read_lock_failed");
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}
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static inline void write_lock(rwlock_t *rw)
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{
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__build_write_lock(rw, "__write_lock_failed");
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}
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#define READ_LOCK(X) read_lock(&(X))
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#define WRITE_LOCK(X) write_lock(&(X))
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#define READ_UNLOCK(rw) asm volatile("lock ; incl %0" :"=m" (__dummy_lock(&(rw))))
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#define WRITE_UNLOCK(rw) asm volatile("lock ; addl $" RW_LOCK_BIAS_STR ",%0":"=m" (__dummy_lock(&(rw))))
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#define INIT_RWLOCK(RW) (RW).lock = RW_LOCK_UNLOCKED
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