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- Modify pmap_is_current() to return FALSE when a pmap's page table is in

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use because a kernel thread is borrowing it.  The borrowed page table
   can change spontaneously, making any dependence on its continued use
   subject to a race condition.
 - _pmap_unwire_pte_hold() cannot use pmap_is_current(): If a change is
   made to a page table page mapping for a borrowed page table, the TLB
   must be updated.

In collaboration with:	tegge
This commit is contained in:
Alan Cox 2003-10-13 03:28:31 +00:00
parent 0986ab12e4
commit 50ac3f9939
1 changed files with 12 additions and 4 deletions
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16
sys/i386/i386/pmap.c
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@ -739,13 +739,17 @@ pmap_invalidate_all(pmap_t pmap)
#endif /* !I386_CPU */
/*
* Are we current address space or kernel?
* Are we current address space or kernel? N.B. We return FALSE when
* a pmap's page table is in use because a kernel thread is borrowing
* it. The borrowed page table can change spontaneously, making any
* dependence on its continued use subject to a race condition.
*/
static __inline int
static int
pmap_is_current(pmap_t pmap)
{
return (pmap == kernel_pmap ||
(pmap->pm_pdir[PTDPTDI] & PG_FRAME) == (PTDpde[0] & PG_FRAME));
(pmap == vmspace_pmap(curthread->td_proc->p_vmspace) &&
(pmap->pm_pdir[PTDPTDI] & PG_FRAME) == (PTDpde[0] & PG_FRAME)));
}
/*
@ -958,7 +962,11 @@ _pmap_unwire_pte_hold(pmap_t pmap, vm_page_t m)
*/
pmap->pm_pdir[m->pindex] = 0;
--pmap->pm_stats.resident_count;
if (pmap_is_current(pmap)) {
/*
* We never unwire a kernel page table page, making a
* check for the kernel_pmap unnecessary.
*/
if ((pmap->pm_pdir[PTDPTDI] & PG_FRAME) == (PTDpde[0] & PG_FRAME)) {
/*
* Do an invltlb to make the invalidated mapping
* take effect immediately.