On 9/13/24 15:57, Ryan Roberts wrote:
On 13/09/2024 09:44, Anshuman Khandual wrote:
Convert PTE accesses via ptep_get() helper that defaults as READ_ONCE() but
also provides the platform an opportunity to override when required.
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: "Mike Rapoport (IBM)" <rppt@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
include/linux/pgtable.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 2a6a3cccfc36..05e6995c1b93 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1060,7 +1060,7 @@ static inline int pgd_same(pgd_t pgd_a, pgd_t pgd_b)
*/
#define set_pte_safe(ptep, pte) \
({ \
- WARN_ON_ONCE(pte_present(*ptep) && !pte_same(*ptep, pte)); \
+ WARN_ON_ONCE(pte_present(ptep_get(ptep)) && !pte_same(ptep_get(ptep), pte)); \
Suggest reading once into a temporary so that the pte can't change between the 2
gets. In practice, it's not likely to be a huge problem for this instance since
its under the PTL so can only be racing with HW update of access and dirty. But
good practice IMHO:
pte_t __old = ptep_get(ptep); \
WARN_ON_ONCE(pte_present(__old) && !pte_same(__old, pte)); \
Sure, will change as suggested.
Thanks,
Ryan
set_pte(ptep, pte); \
})
