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Avoid a LOR by unlocking the vm_page_queue_mtx before calling uma_zalloc,

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and freeing the allocated memory if another thread already did the same.
This commit is contained in:
Olivier Houchard 2006-05-31 15:52:11 +00:00
parent 4cd3385ee3
commit c7f17eb45c
1 changed files with 35 additions and 5 deletions
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40
sys/arm/arm/pmap.c
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@ -915,20 +915,38 @@ pmap_alloc_l2_bucket(pmap_t pm, vm_offset_t va)
l1idx = L1_IDX(va);
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
if ((l2 = pm->pm_l2[L2_IDX(l1idx)]) == NULL) {
/*
* No mapping at this address, as there is
* no entry in the L1 table.
* Need to allocate a new l2_dtable.
*/
again_l2table:
vm_page_unlock_queues();
if ((l2 = pmap_alloc_l2_dtable()) == NULL) {
vm_page_lock_queues();
return (NULL);
}
bzero(l2, sizeof(*l2));
/*
* Link it into the parent pmap
*/
pm->pm_l2[L2_IDX(l1idx)] = l2;
vm_page_lock_queues();
if (pm->pm_l2[L2_IDX(l1idx)] != NULL) {
vm_page_unlock_queues();
uma_zfree(l2table_zone, l2);
vm_page_lock_queues();
l2 = pm->pm_l2[L2_IDX(l1idx)];
if (l2 == NULL)
goto again_l2table;
/*
* Someone already allocated the l2_dtable while
* we were doing the same.
*/
} else {
bzero(l2, sizeof(*l2));
/*
* Link it into the parent pmap
*/
pm->pm_l2[L2_IDX(l1idx)] = l2;
}
}
l2b = &l2->l2_bucket[L2_BUCKET(l1idx)];
@ -943,7 +961,19 @@ pmap_alloc_l2_bucket(pmap_t pm, vm_offset_t va)
* No L2 page table has been allocated. Chances are, this
* is because we just allocated the l2_dtable, above.
*/
again_ptep:
vm_page_unlock_queues();
ptep = (void*)uma_zalloc(l2zone, M_NOWAIT);
vm_page_lock_queues();
if (l2b->l2b_kva != 0) {
/* We lost the race. */
vm_page_unlock_queues();
uma_zfree(l2zone, ptep);
vm_page_lock_queues();
if (l2b->l2b_kva == 0)
goto again_ptep;
return (l2b);
}
l2b->l2b_phys = vtophys(ptep);
if (ptep == NULL) {
/*