Commit 362a61ad6119 ("fix SMP data race in pagetable setup vs walking")
added the following:
+ smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
+
spin_lock(&mm->page_table_lock);
However, over the years the fence along with the comment got moved
around the file, eventually landing in a spot where it is *NOT* followed
by a lock acquire (or any other operation which might happen to provide
any fence on a given arch), rendering the comment stale.
Signed-off-by: Mateusz Guzik <mjguzik@xxxxxxxxx>
---
./scripts/get_maintainer.pl only showed akpm@ and the lists, adding the
--git switch showed more names, but I only picked some of them. I don't
know who makes the most sense to add here.
I fully concede I could not be arsed to check if the fence is still
needed to begin with, I ran into this while looking at something else.
The comment puzzled me for a minute suggesting pmd_populate has an
immediate lock acquire inside.
mm/memory.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c
index 34f8402d2046..0a6893833fac 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -436,7 +436,7 @@ void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte)
* seen in-order. See the alpha page table accessors for the
* smp_rmb() barriers in page table walking code.
*/
- smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
+ smp_wmb();
pmd_populate(mm, pmd, *pte);
*pte = NULL;
}
--
2.43.0
