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Fixed possible deadlock from recursive INTs on same cpu. Since

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we use lazy masking INTREN()/INTRDIS() might be called with INTs enabled.
This means another higher prio INT to the same cpu could attempt to
re-enter the critical region, but would spin waiting for the lock.  Since
it is the owner, it would deadlock.
This commit is contained in:
Steve Passe 1997-07-23 21:25:31 +00:00
parent f8eb25da54
commit e78205df5b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=27636
1 changed files with 9 additions and 3 deletions
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12
sys/i386/isa/apic_ipl.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: apic_ipl.s,v 1.18 1997/07/23 20:18:14 smp Exp smp $
* $Id: apic_ipl.s,v 1.19 1997/07/23 21:18:30 smp Exp smp $
*/
@ -254,9 +254,11 @@ bad_mask: .asciz "bad mask"
ALIGN_TEXT
.globl _INTREN
_INTREN:
pushfl /* save state of EI flag */
cli /* prevent recursion */
IMASK_LOCK /* enter critical reg */
movl 4(%esp), %eax /* mask into %eax */
movl 8(%esp), %eax /* mask into %eax */
bsfl %eax, %ecx /* get pin index */
btrl %ecx, _apic_imen /* update _apic_imen */
@ -273,6 +275,7 @@ _INTREN:
movl %eax, 16(%edx) /* write the APIC register data */
IMASK_UNLOCK /* exit critical reg */
popfl /* restore old state of EI flag */
ret
/*
@ -285,9 +288,11 @@ _INTREN:
ALIGN_TEXT
.globl _INTRDIS
_INTRDIS:
pushfl /* save state of EI flag */
cli /* prevent recursion */
IMASK_LOCK /* enter critical reg */
movl 4(%esp), %eax /* mask into %eax */
movl 8(%esp), %eax /* mask into %eax */
bsfl %eax, %ecx /* get pin index */
btsl %ecx, _apic_imen /* update _apic_imen */
@ -304,6 +309,7 @@ _INTRDIS:
movl %eax, 16(%edx) /* write the APIC register data */
IMASK_UNLOCK /* exit critical reg */
popfl /* restore old state of EI flag */
ret