kernel-ark/arch/sparc/lib/locks.S
Al Viro 7a39f52202 [PATCH] sparc32 rwlock fix
read_trylock() is broken on sparc32 (doesn't build and didn't work
right, actually).  Proposed fix:

 - make "writer holds lock" distinguishable from "reader tries to grab
   lock"

 - have __raw_read_trylock() try to acquire the mutex (in LSB of lock),
   terminating spin if we see that there's writer holding it.  Then do
   the rest as we do in read_lock().

Thanks to Ingo for discussion...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-08 12:32:35 -07:00

93 lines
2.0 KiB
ArmAsm

/* $Id: locks.S,v 1.16 2000/02/26 11:02:47 anton Exp $
* locks.S: SMP low-level lock primitives on Sparc.
*
* Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
* Copyright (C) 1998 Anton Blanchard (anton@progsoc.uts.edu.au)
* Copyright (C) 1998 Jakub Jelinek (jj@ultra.linux.cz)
*/
#include <asm/ptrace.h>
#include <asm/psr.h>
#include <asm/smp.h>
#include <asm/spinlock.h>
.text
.align 4
/* 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_read_try_spin_on_wlock:
andcc %g2, 0xff, %g0
be,a ___rw_read_try
ldstub [%g1 + 3], %g2
xnorcc %g2, 0x0, %o0 /* if g2 is ~0, set o0 to 0 and bugger off */
bne,a ___rw_read_enter_spin_on_wlock
ld [%g1], %g2
retl
mov %g4, %o7
___rw_read_exit_spin_on_wlock:
orcc %g2, 0x0, %g0
be,a ___rw_read_exit
ldstub [%g1 + 3], %g2
b ___rw_read_exit_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
ld [%g1], %g2
.globl ___rw_read_enter
___rw_read_enter:
orcc %g2, 0x0, %g0
bne,a ___rw_read_enter_spin_on_wlock
ldub [%g1 + 3], %g2
ld [%g1], %g2
add %g2, 1, %g2
st %g2, [%g1]
retl
mov %g4, %o7
.globl ___rw_read_exit
___rw_read_exit:
orcc %g2, 0x0, %g0
bne,a ___rw_read_exit_spin_on_wlock
ldub [%g1 + 3], %g2
ld [%g1], %g2
sub %g2, 0x1ff, %g2
st %g2, [%g1]
retl
mov %g4, %o7
.globl ___rw_read_try
___rw_read_try:
orcc %g2, 0x0, %g0
bne ___rw_read_try_spin_on_wlock
ld [%g1], %g2
add %g2, 1, %g2
st %g2, [%g1]
set 1, %o1
retl
mov %g4, %o7
.globl ___rw_write_enter
___rw_write_enter:
orcc %g2, 0x0, %g0
bne ___rw_write_enter_spin_on_wlock
ld [%g1], %g2
andncc %g2, 0xff, %g0
bne,a ___rw_write_enter_spin_on_wlock
stb %g0, [%g1 + 3]
retl
mov %g4, %o7