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Eliminate the blocking of INTs while spinning for the safe simplelock.

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This commit is contained in:
Steve Passe 1997-08-25 21:02:59 +00:00
parent 8e30c09987
commit 047307e09d
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=28736
1 changed files with 9 additions and 8 deletions
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17
sys/i386/i386/simplelock.s
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@ -22,7 +22,7 @@
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $Id: simplelock.s,v 1.6 1997/08/23 04:10:11 smp Exp smp $
* $Id: simplelock.s,v 1.3 1997/08/24 00:05:37 fsmp Exp $
*/
/*
@ -168,20 +168,21 @@ ENTRY(test_and_set)
* void ss_lock(struct simplelock *lkp)
*/
ENTRY(ss_lock)
movl lapic_tpr, %eax
movl $TPR_BLOCK_HWI, lapic_tpr
movl %eax, _ss_tpr
movl 4(%esp), %eax /* get the address of the lock */
movl $1, %ecx
movl $1, %ecx /* value for a held lock */
ssetlock:
xchgl %ecx, (%eax)
pushl lapic_tpr /* save current task priority */
movl $TPR_BLOCK_HWI, lapic_tpr /* block hw INTs */
xchgl %ecx, (%eax) /* compete */
testl %ecx, %ecx
jz sgotit /* it was clear, return */
popl lapic_tpr /* previous value while waiting */
swait:
cmpl $0, (%eax) /* wait to empty */
jne swait /* still set... */
jmp ssetlock /* empty again, try once more */
sgotit:
popl _ss_tpr /* save the old task priority */
ret
/*
@ -189,7 +190,7 @@ sgotit:
*/
ENTRY(ss_unlock)
movl 4(%esp), %eax /* get the address of the lock */
movl $0, (%eax)
movl $0, (%eax) /* clear the simple lock */
movl _ss_tpr, %eax
movl %eax, lapic_tpr
movl %eax, lapic_tpr /* restore the old task priority */
ret