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/* $Id: rwlock.S,v 1.1.1.1 2004-04-15 01:33:47 phoenix Exp $
 * rwlocks.S: These things are too big to do inline.
 *
 * Copyright (C) 1999 David S. Miller (davem@redhat.com)
 */

        .text
        .align  64

        .globl  rwlock_impl_begin, rwlock_impl_end

        /* The non-contention read lock usage is 2 cache lines. */

        .globl  __read_lock, __read_unlock
rwlock_impl_begin:
__read_lock: /* %o0 = lock_ptr */
        ldsw            [%o0], %g5
        brlz,pn         %g5, __read_wait_for_writer
4:       add            %g5, 1, %g7
        cas             [%o0], %g5, %g7
        cmp             %g5, %g7
        bne,pn          %icc, __read_lock
         membar         #StoreLoad | #StoreStore
99:     retl
         nop
__read_unlock: /* %o0 = lock_ptr */
        lduw            [%o0], %g5
        sub             %g5, 1, %g7
        cas             [%o0], %g5, %g7
        cmp             %g5, %g7
        be,pt           %xcc, 99b
         membar         #StoreLoad | #StoreStore
        ba,a,pt         %xcc, __read_unlock

__read_wait_for_writer:
        ldsw            [%o0], %g5
        brlz,pt         %g5, __read_wait_for_writer
         membar         #LoadLoad
        ba,a,pt         %xcc, 4b
__write_wait_for_any:
        lduw            [%o0], %g5
        brnz,pt         %g5, __write_wait_for_any
         membar         #LoadLoad
        ba,a,pt         %xcc, 4f

        .align          64
        .globl          __write_unlock
__write_unlock: /* %o0 = lock_ptr */
        membar          #LoadStore | #StoreStore
        retl
         stw            %g0, [%o0]

        .globl          __write_lock
__write_lock: /* %o0 = lock_ptr */
        sethi           %hi(0x80000000), %g2

1:      lduw            [%o0], %g5
        brnz,pn         %g5, __write_wait_for_any
4:       or             %g5, %g2, %g7
        cas             [%o0], %g5, %g7

        cmp             %g5, %g7
        be,pt           %icc, 99b
         membar         #StoreLoad | #StoreStore
        ba,a,pt         %xcc, 1b
rwlock_impl_end: