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authorLinus Torvalds <torvalds@linux-foundation.org>2014-12-20 16:48:59 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-20 16:48:59 -0800
commit60815cf2e05057db5b78e398d9734c493560b11e (patch)
tree23d7f55df13cc5a0c072cc8a6f361f8e7050b825 /mm
parentbfc7249cc293deac8f2678b7ec3d2407b68c0a33 (diff)
parent5de72a2247ac05bde7c89039631b3d0c6186fafb (diff)
downloadop-kernel-dev-60815cf2e05057db5b78e398d9734c493560b11e.zip
op-kernel-dev-60815cf2e05057db5b78e398d9734c493560b11e.tar.gz
Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux
Pull ACCESS_ONCE cleanup preparation from Christian Borntraeger: "kernel: Provide READ_ONCE and ASSIGN_ONCE As discussed on LKML http://marc.info/?i=54611D86.4040306%40de.ibm.com ACCESS_ONCE might fail with specific compilers for non-scalar accesses. Here is a set of patches to tackle that problem. The first patch introduce READ_ONCE and ASSIGN_ONCE. If the data structure is larger than the machine word size memcpy is used and a warning is emitted. The next patches fix up several in-tree users of ACCESS_ONCE on non-scalar types. This does not yet contain a patch that forces ACCESS_ONCE to work only on scalar types. This is targetted for the next merge window as Linux next already contains new offenders regarding ACCESS_ONCE vs. non-scalar types" * tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux: s390/kvm: REPLACE barrier fixup with READ_ONCE arm/spinlock: Replace ACCESS_ONCE with READ_ONCE arm64/spinlock: Replace ACCESS_ONCE READ_ONCE mips/gup: Replace ACCESS_ONCE with READ_ONCE x86/gup: Replace ACCESS_ONCE with READ_ONCE x86/spinlock: Replace ACCESS_ONCE with READ_ONCE mm: replace ACCESS_ONCE with READ_ONCE or barriers kernel: Provide READ_ONCE and ASSIGN_ONCE
Diffstat (limited to 'mm')
-rw-r--r--mm/gup.c2
-rw-r--r--mm/memory.c11
-rw-r--r--mm/rmap.c3
3 files changed, 13 insertions, 3 deletions
diff --git a/mm/gup.c b/mm/gup.c
index 0ca1df9..a900759 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -968,7 +968,7 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
pudp = pud_offset(&pgd, addr);
do {
- pud_t pud = ACCESS_ONCE(*pudp);
+ pud_t pud = READ_ONCE(*pudp);
next = pud_addr_end(addr, end);
if (pud_none(pud))
diff --git a/mm/memory.c b/mm/memory.c
index d8aebc5..649e7d44 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3195,7 +3195,16 @@ static int handle_pte_fault(struct mm_struct *mm,
pte_t entry;
spinlock_t *ptl;
- entry = ACCESS_ONCE(*pte);
+ /*
+ * some architectures can have larger ptes than wordsize,
+ * e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and CONFIG_32BIT=y,
+ * so READ_ONCE or ACCESS_ONCE cannot guarantee atomic accesses.
+ * The code below just needs a consistent view for the ifs and
+ * we later double check anyway with the ptl lock held. So here
+ * a barrier will do.
+ */
+ entry = *pte;
+ barrier();
if (!pte_present(entry)) {
if (pte_none(entry)) {
if (vma->vm_ops) {
diff --git a/mm/rmap.c b/mm/rmap.c
index 45ba250..c5bc241 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -583,7 +583,8 @@ pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
* without holding anon_vma lock for write. So when looking for a
* genuine pmde (in which to find pte), test present and !THP together.
*/
- pmde = ACCESS_ONCE(*pmd);
+ pmde = *pmd;
+ barrier();
if (!pmd_present(pmde) || pmd_trans_huge(pmde))
pmd = NULL;
out:
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