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/* $Id: locks.S,v 1.13 1998/07/30 11:29:28 davem Exp $
* locks.S: SMP low-level lock primitives on Sparc.
*
* Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
*/
#include <asm/cprefix.h>
#include <asm/ptrace.h>
#include <asm/psr.h>
#include <asm/smp.h>
#include <asm/spinlock.h>
.text
.align 4
/* This is called when the initial acquisition attempt of a spin
* lock fails. The calling convention is weird, return address
* is in %o7 as usual but we agree with the caller to only touch
* and use %g2 as a temporary. We are passed a ptr to the lock
* itself in %g1, %g4 must be restored into %o7 when we return,
* and the caller wants us to return to him at three instructions
* previous to the call instruction which got us here. See how
* this is used in asm/spinlock.h if what I just said confuses
* you to no end.
*/
.globl ___spinlock_waitfor
___spinlock_waitfor:
1: orcc %g2, 0x0, %g0
bne,a 1b
ldub [%g1], %g2
ldstub [%g1], %g2
jmpl %o7 - 12, %g0
mov %g4, %o7
/* Read/writer locks, as usual this is overly clever to make it
* as fast as possible.
*/
/* caches... */
___rw_read_enter_spin_on_wlock:
orcc %g2, 0x0, %g0
be,a ___rw_read_enter
ldstub [%g1 + 3], %g2
b ___rw_read_enter_spin_on_wlock
ldub [%g1 + 3], %g2
___rw_write_enter_spin_on_wlock:
orcc %g2, 0x0, %g0
be,a ___rw_write_enter
ldstub [%g1 + 3], %g2
b ___rw_write_enter_spin_on_wlock
ldub [%g1 + 3], %g2
.globl ___rw_read_enter
___rw_read_enter:
orcc %g2, 0x0, %g0
bne,a ___rw_read_enter_spin_on_wlock
ldub [%g1 + 3], %g2
1:
ldstub [%g1 + 2], %g7
orcc %g7, 0x0, %g0
bne 1b
ldsh [%g1], %g2
add %g2, 1, %g2
sth %g2, [%g1]
sth %g0, [%g1 + 2]
retl
mov %g4, %o7
/* We must be careful here to not blow away wlock. */
.globl ___rw_read_exit
___rw_read_exit_spin:
ldstub [%g1 + 2], %g2
___rw_read_exit:
orcc %g2, 0x0, %g0
bne ___rw_read_exit_spin
ldsh [%g1], %g7
sub %g7, 1, %g7
sth %g7, [%g1]
stb %g0, [%g1 + 2]
retl
mov %g4, %o7
.globl ___rw_write_enter
___rw_write_enter:
orcc %g2, 0x0, %g0
bne,a ___rw_write_enter_spin_on_wlock
ldub [%g1 + 3], %g2
ld [%g1], %g2
1:
andncc %g2, 0xff, %g0
bne,a 1b
ld [%g1], %g2
retl
mov %g4, %o7
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