126 lines
3.7 KiB
C
126 lines
3.7 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 1.4 2007-11-26 23:43:09 vsc 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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typedef struct {
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volatile unsigned int lock;
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} spinlock_t;
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static inline int
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spin_trylock(spinlock_t *lock)
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{
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char tmp = 1;
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__asm__ __volatile__(
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"xchgb %b0, %1"
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: "=q"(tmp), "=m"(lock->lock)
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: "0"(tmp) : "memory");
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return tmp == 0;
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}
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static inline void
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spin_unlock(spinlock_t *lock)
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{
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/* To unlock we move 0 to the lock.
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* On i386 this needs to be a locked operation
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* to avoid Pentium Pro errata 66 and 92.
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*/
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#if defined(__x86_64__)
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__asm__ __volatile__("" : : : "memory");
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*(unsigned char*)&lock->lock = 0;
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#else
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char tmp = 0;
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__asm__ __volatile__(
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"xchgb %b0, %1"
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: "=q"(tmp), "=m"(lock->lock)
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: "0"(tmp) : "memory");
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#endif
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}
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#define TRY_LOCK(LOCK_VAR) spin_trylock((spinlock_t *)(LOCK_VAR))
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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) spin_unlock((spinlock_t *)&(LOCK_VAR))
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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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