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

1 files changed, 6 insertions, 12 deletions

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 8b9ccf02a2c5..8a1be9017730 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -227,12 +227,10 @@ static void ipte_lock_simple(struct kvm_vcpu *vcpu)
                 goto out;
         ic = &vcpu->kvm->arch.sca->ipte_control;
         do {
-                old = *ic;
-                barrier();
+                old = READ_ONCE(*ic);
                 while (old.k) {
                         cond_resched();
-                        old = *ic;
-                        barrier();
+                        old = READ_ONCE(*ic);
                 }
                 new = old;
                 new.k = 1;
@@ -251,8 +249,7 @@ static void ipte_unlock_simple(struct kvm_vcpu *vcpu)
                 goto out;
         ic = &vcpu->kvm->arch.sca->ipte_control;
         do {
-                old = *ic;
-                barrier();
+                old = READ_ONCE(*ic);
                 new = old;
                 new.k = 0;
         } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
@@ -267,12 +264,10 @@ static void ipte_lock_siif(struct kvm_vcpu *vcpu)
 
         ic = &vcpu->kvm->arch.sca->ipte_control;
         do {
-                old = *ic;
-                barrier();
+                old = READ_ONCE(*ic);
                 while (old.kg) {
                         cond_resched();
-                        old = *ic;
-                        barrier();
+                        old = READ_ONCE(*ic);
                 }
                 new = old;
                 new.k = 1;
@@ -286,8 +281,7 @@ static void ipte_unlock_siif(struct kvm_vcpu *vcpu)
 
         ic = &vcpu->kvm->arch.sca->ipte_control;
         do {
-                old = *ic;
-                barrier();
+                old = READ_ONCE(*ic);
                 new = old;
                 new.kh--;
                 if (!new.kh)