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cc: freebsd-smp@freebsd.org
Subject: Finished locks..
In-reply-to: Your message of Tue, 03 Dec 1996 00:54:40 -0600.
             <199612030654.AAA12221@friley216.res.iastate.edu> 
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Date: Tue, 03 Dec 1996 15:08:32 -0600
From: Chris Csanady <ccsanady@friley216.res.iastate.edu>
Sender: owner-smp@freebsd.org
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Precedence: bulk

For what it's worth, I have completed a simple implementation of spin
locks.  (However, I'm sure someone will tell me different.. :)  Either
way, it was nice to learn a bit of assembly.

If these are not sufficient, how can I improve upon them?  I'd like to
move some of the locking around, and they would help.  In particular, I
am planning to move the global lock out into the syscalls, and perhaps
create a seperate lock for the run queues and such.  Then from there, we
can we can reduce the graininess a bit. :)

Anyway, I'd just like to thank all of you for helping me out.

Chris



        .text

/***********************************************************************
 *  void LOCK()
 *  -----------------
 *  All registers preserved
 */

        .align  2,0x90
        .globl  _LOCK
_LOCK:
        pushl   %eax
        pushl   %ecx
        pushl   %edx
        movl    $_smp_active, %eax
        cmpl    $0, %eax
        je      4f
1:      movl    16(%esp), %edx
        movl    $1, %ecx
        movl    $0, %eax
2:      lock
        cmpxchg %ecx, (%edx)
        jne     3f
        jmp     4f
3:      cmpl    %ecx, (%edx)
        je      3b
        jmp     2b
4:      popl    %edx
        popl    %ecx
        popl    %eax
        ret

/***********************************************************************
 *  int TRY_LOCK()
 *  -----------------
 *  reg %eax == 1 if success
 */

        .align  2,0x90
        .globl  _TRY_LOCK
_TRY_LOCK:
        pushl   %ecx
        pushl   %edx
        movl    $_smp_active, %eax
        cmpl    $0, %eax
        je      1f
        movl    12(%esp), %edx
        movl    $1, %ecx
        movl    $0, %eax
        lock
        cmpxchg %ecx, (%edx)
        jne     1f
        movl    $1, %eax
        jmp     2f
1:      movl    $0, %eax
2:      popl    %edx
        popl    %ecx
        ret

/***********************************************************************
 *  void UNLOCK()
 *  -----------------
 *  All registers preserved
 */

        .align  2,0x90
        .globl  _UNLOCK
_UNLOCK:
        pushl   %ecx
        movl    8(%esp), %ecx
        movl    $0, (%ecx)
        popl    %ecx
        ret