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pushed down "volatility" of simplelock to actual int inside the struct.

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Submitted by:    bde@zeta.org.a
This commit is contained in:
Steve Passe 1997-08-04 19:14:56 +00:00
parent 9d37772f68
commit 28f53d312c
2 changed files with 14 additions and 12 deletions
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16
sys/i386/i386/simplelock.s
View File

@ -22,7 +22,7 @@
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $Id$
* $Id: simplelock.s,v 1.1 1997/07/24 23:51:33 fsmp Exp $
*/
/*
@ -35,6 +35,8 @@
/*
* The following impliments the primitives described in i386/i386/param.h
* necessary for the Lite2 lock manager system.
* The major difference is that the "volatility" of the lock datum has been
* pushed down from the various functions to lock_data itself.
*/
/*
@ -46,7 +48,7 @@
* only be used for exclusive locks.
*
* struct simplelock {
* int lock_data;
* volatile int lock_data;
* };
*/
@ -65,7 +67,7 @@ ENTRY(s_lock_init)
/*
* void
* s_lock(__volatile struct simplelock *lkp)
* s_lock(struct simplelock *lkp)
* {
* while (test_and_set(&lkp->lock_data))
* continue;
@ -73,7 +75,7 @@ ENTRY(s_lock_init)
*
* Note:
* If the acquire fails we do a loop of reads waiting for the lock to
* become free instead of continually beating on the lock with btsl.
* become free instead of continually beating on the lock with xchgl.
* The theory here is that the CPU will stay within its cache until
* a write by the other CPU updates it, instead of continually updating
* the local cache (and thus causing external bus writes) with repeated
@ -96,7 +98,7 @@ gotit:
/*
* int
* s_lock_try(__volatile struct simplelock *lkp)
* s_lock_try(struct simplelock *lkp)
* {
* return (!test_and_set(&lkp->lock_data));
* }
@ -115,7 +117,7 @@ ENTRY(s_lock_try)
/*
* void
* s_unlock(__volatile struct simplelock *lkp)
* s_unlock(struct simplelock *lkp)
* {
* lkp->lock_data = 0;
* }
@ -129,7 +131,7 @@ ENTRY(s_unlock)
#ifdef needed
/*
* test_and_set(struct simplelock *lkp);
* int test_and_set(struct simplelock *lkp);
*/
ENTRY(test_and_set)
movl 4(%esp), %eax /* get the address of the lock */

10
sys/i386/include/param.h
View File

@ -34,7 +34,7 @@
* SUCH DAMAGE.
*
* from: @(#)param.h 5.8 (Berkeley) 6/28/91
* $Id: param.h,v 1.4 1997/07/24 03:06:19 smp Exp smp $
* $Id: param.h,v 1.30 1997/07/24 23:48:51 fsmp Exp $
*/
#ifndef _MACHINE_PARAM_H_
@ -140,7 +140,7 @@
* of these locks while a process is sleeping.
*/
struct simplelock {
int lock_data __attribute__ ((aligned (4)));
volatile int lock_data;
};
#if !defined(SIMPLELOCK_DEBUG) && NCPUS > 1
@ -163,7 +163,7 @@ simple_lock_init(struct simplelock *lkp)
}
static __inline void
simple_lock(__volatile struct simplelock *lkp)
simple_lock(struct simplelock *lkp)
{
while (test_and_set(&lkp->lock_data))
@ -171,14 +171,14 @@ simple_lock(__volatile struct simplelock *lkp)
}
static __inline int
simple_lock_try(__volatile struct simplelock *lkp)
simple_lock_try(struct simplelock *lkp)
{
return (!test_and_set(&lkp->lock_data));
}
static __inline void
simple_unlock(__volatile struct simplelock *lkp)
simple_unlock(struct simplelock *lkp)
{
lkp->lock_data = 0;