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SubjectRe: [patch 2.4.11-pre5] atomic_dec_and_lock() for alpha
On Tue, Oct 09, 2001 at 02:30:13PM +0400, Ivan Kokshaysky wrote:
> OK. I prefer the latter - rewriting in assembly won't allow DEBUG_SPINLOCK
> stuff in this function. OTOH, moving the return outside an asm statement
> adds only one instruction - conditional branch that falls through in the
> fast path.

Hmm. What about a mixture:


asm (".text \n\
.global atomic_dec_and_lock \n\
.ent atomic_dec_and_lock \n\
atomic_dec_and_lock: \n\
.prologue 0 \n\
1: ldl_l $1, 0($16) \n\
subl $1, 1, $1 \n\
beq 2f \n\
stl_c $1, 0($16) \n\
beq $1, 3f \n\
mb \n\
ret \n\
.align 4 \n\
3: br 1b \n\
2: lda $27, atomic_dec_and_lock_1");

/* FALLTHRU */

static int
atomic_dec_and_lock_1(atomic_t *atomic, spinlock_t *lock)
{
/* Slow path */
spin_lock(lock);
if (atomic_dec_and_test(atomic))
return 1;
spin_unlock(lock);
return 0;
}


r~
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