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Use the generation count of the pv list to work around LOR between

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pmap lock and pv list lock, and use the shared locking on
pvh_global_lock in pmap_remove_write(), same as it was done for
pmap_ts_referenced().

Noted and reviewed by:	alc (previous version)
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Konstantin Belousov 2013-08-22 18:05:31 +00:00
parent c01bf4edad
commit b544368a22
1 changed files with 37 additions and 6 deletions
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43
sys/amd64/amd64/pmap.c
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@ -4765,10 +4765,12 @@ pmap_remove_write(vm_page_t m)
{
struct md_page *pvh;
pmap_t pmap;
struct rwlock *lock;
pv_entry_t next_pv, pv;
pd_entry_t *pde;
pt_entry_t oldpte, *pte;
vm_offset_t va;
int pvh_gen, md_gen;
KASSERT((m->oflags & VPO_UNMANAGED) == 0,
("pmap_remove_write: page %p is not managed", m));
@ -4781,23 +4783,51 @@ pmap_remove_write(vm_page_t m)
VM_OBJECT_ASSERT_WLOCKED(m->object);
if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
return;
rw_wlock(&pvh_global_lock);
rw_rlock(&pvh_global_lock);
lock = VM_PAGE_TO_PV_LIST_LOCK(m);
pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
retry_pv_loop:
rw_wlock(lock);
if ((m->flags & PG_FICTITIOUS) != 0)
goto small_mappings;
pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
TAILQ_FOREACH_SAFE(pv, &pvh->pv_list, pv_next, next_pv) {
pmap = PV_PMAP(pv);
PMAP_LOCK(pmap);
if (!PMAP_TRYLOCK(pmap)) {
pvh_gen = pvh->pv_gen;
rw_wunlock(lock);
PMAP_LOCK(pmap);
rw_wlock(lock);
if (pvh_gen != pvh->pv_gen) {
PMAP_UNLOCK(pmap);
rw_wunlock(lock);
goto retry_pv_loop;
}
}
va = pv->pv_va;
pde = pmap_pde(pmap, va);
if ((*pde & PG_RW) != 0)
(void)pmap_demote_pde(pmap, pde, va);
(void)pmap_demote_pde_locked(pmap, pde, va, &lock);
KASSERT(lock == VM_PAGE_TO_PV_LIST_LOCK(m),
("inconsistent pv lock %p %p for page %p",
lock, VM_PAGE_TO_PV_LIST_LOCK(m), m));
PMAP_UNLOCK(pmap);
}
small_mappings:
TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
pmap = PV_PMAP(pv);
PMAP_LOCK(pmap);
if (!PMAP_TRYLOCK(pmap)) {
pvh_gen = pvh->pv_gen;
md_gen = m->md.pv_gen;
rw_wunlock(lock);
PMAP_LOCK(pmap);
rw_wlock(lock);
if (pvh_gen != pvh->pv_gen ||
md_gen != m->md.pv_gen) {
PMAP_UNLOCK(pmap);
rw_wunlock(lock);
goto retry_pv_loop;
}
}
pde = pmap_pde(pmap, pv->pv_va);
KASSERT((*pde & PG_PS) == 0,
("pmap_remove_write: found a 2mpage in page %p's pv list",
@ -4815,8 +4845,9 @@ pmap_remove_write(vm_page_t m)
}
PMAP_UNLOCK(pmap);
}
rw_wunlock(lock);
vm_page_aflag_clear(m, PGA_WRITEABLE);
rw_wunlock(&pvh_global_lock);
rw_runlock(&pvh_global_lock);
}
/*