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Commit 60815cf2 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents bfc7249c 5de72a22

arch/arm/include/asm/spinlock.h

+2 −2
Original line number Original line Diff line number Diff line
@@ -120,12 +120,12 @@ static inline int arch_spin_value_unlocked(arch_spinlock_t lock) 




static inline int arch_spin_is_locked(arch_spinlock_t *lock)

static inline int arch_spin_is_locked(arch_spinlock_t *lock)

{

{

	return !arch_spin_value_unlocked(ACCESS_ONCE(*lock));

	return !arch_spin_value_unlocked(READ_ONCE(*lock));

}

}





static inline int arch_spin_is_contended(arch_spinlock_t *lock)

static inline int arch_spin_is_contended(arch_spinlock_t *lock)

{

{

	struct __raw_tickets tickets = ACCESS_ONCE(lock->tickets);

	struct __raw_tickets tickets = READ_ONCE(lock->tickets);

	return (tickets.next - tickets.owner) > 1;

	return (tickets.next - tickets.owner) > 1;

}

}

#define arch_spin_is_contended	arch_spin_is_contended

#define arch_spin_is_contended	arch_spin_is_contended

arch/arm64/include/asm/spinlock.h

+2 −2
Original line number Original line Diff line number Diff line
@@ -99,12 +99,12 @@ static inline int arch_spin_value_unlocked(arch_spinlock_t lock) 




static inline int arch_spin_is_locked(arch_spinlock_t *lock)

static inline int arch_spin_is_locked(arch_spinlock_t *lock)

{

{

	return !arch_spin_value_unlocked(ACCESS_ONCE(*lock));

	return !arch_spin_value_unlocked(READ_ONCE(*lock));

}

}





static inline int arch_spin_is_contended(arch_spinlock_t *lock)

static inline int arch_spin_is_contended(arch_spinlock_t *lock)

{

{

	arch_spinlock_t lockval = ACCESS_ONCE(*lock);

	arch_spinlock_t lockval = READ_ONCE(*lock);

	return (lockval.next - lockval.owner) > 1;

	return (lockval.next - lockval.owner) > 1;

}

}

#define arch_spin_is_contended	arch_spin_is_contended

#define arch_spin_is_contended	arch_spin_is_contended

arch/mips/mm/gup.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -30,7 +30,7 @@ static inline pte_t gup_get_pte(pte_t *ptep) 




	return pte;

	return pte;

#else

#else

	return ACCESS_ONCE(*ptep);

	return READ_ONCE(*ptep);

#endif

#endif

}

}

arch/s390/kvm/gaccess.c

+6 −12
Original line number Original line Diff line number Diff line
@@ -227,12 +227,10 @@ static void ipte_lock_simple(struct kvm_vcpu *vcpu) 
		goto out;

		goto out;

	ic = &vcpu->kvm->arch.sca->ipte_control;

	ic = &vcpu->kvm->arch.sca->ipte_control;

	do {

	do {

		old = *ic;

		old = READ_ONCE(*ic);

		barrier();

		while (old.k) {

		while (old.k) {

			cond_resched();

			cond_resched();

			old = *ic;

			old = READ_ONCE(*ic);

			barrier();

		}

		}

		new = old;

		new = old;

		new.k = 1;

		new.k = 1;
@@ -251,8 +249,7 @@ static void ipte_unlock_simple(struct kvm_vcpu *vcpu) 
		goto out;

		goto out;

	ic = &vcpu->kvm->arch.sca->ipte_control;

	ic = &vcpu->kvm->arch.sca->ipte_control;

	do {

	do {

		old = *ic;

		old = READ_ONCE(*ic);

		barrier();

		new = old;

		new = old;

		new.k = 0;

		new.k = 0;

	} while (cmpxchg(&ic->val, old.val, new.val) != old.val);

	} 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;

	ic = &vcpu->kvm->arch.sca->ipte_control;

	do {

	do {

		old = *ic;

		old = READ_ONCE(*ic);

		barrier();

		while (old.kg) {

		while (old.kg) {

			cond_resched();

			cond_resched();

			old = *ic;

			old = READ_ONCE(*ic);

			barrier();

		}

		}

		new = old;

		new = old;

		new.k = 1;

		new.k = 1;
@@ -286,8 +281,7 @@ static void ipte_unlock_siif(struct kvm_vcpu *vcpu) 




	ic = &vcpu->kvm->arch.sca->ipte_control;

	ic = &vcpu->kvm->arch.sca->ipte_control;

	do {

	do {

		old = *ic;

		old = READ_ONCE(*ic);

		barrier();

		new = old;

		new = old;

		new.kh--;

		new.kh--;

		if (!new.kh)

		if (!new.kh)

arch/x86/include/asm/spinlock.h

+4 −4
Original line number Original line Diff line number Diff line
@@ -92,7 +92,7 @@ static __always_inline void arch_spin_lock(arch_spinlock_t *lock) 
		unsigned count = SPIN_THRESHOLD;

		unsigned count = SPIN_THRESHOLD;





		do {

		do {

			if (ACCESS_ONCE(lock->tickets.head) == inc.tail)

			if (READ_ONCE(lock->tickets.head) == inc.tail)

				goto out;

				goto out;

			cpu_relax();

			cpu_relax();

		} while (--count);

		} while (--count);
@@ -105,7 +105,7 @@ static __always_inline int arch_spin_trylock(arch_spinlock_t *lock) 
{

{

	arch_spinlock_t old, new;

	arch_spinlock_t old, new;





	old.tickets = ACCESS_ONCE(lock->tickets);

	old.tickets = READ_ONCE(lock->tickets);

	if (old.tickets.head != (old.tickets.tail & ~TICKET_SLOWPATH_FLAG))

	if (old.tickets.head != (old.tickets.tail & ~TICKET_SLOWPATH_FLAG))

		return 0;

		return 0;
@@ -162,14 +162,14 @@ static __always_inline void arch_spin_unlock(arch_spinlock_t *lock) 




static inline int arch_spin_is_locked(arch_spinlock_t *lock)

static inline int arch_spin_is_locked(arch_spinlock_t *lock)

{

{

	struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets);

	struct __raw_tickets tmp = READ_ONCE(lock->tickets);





	return tmp.tail != tmp.head;

	return tmp.tail != tmp.head;

}

}





static inline int arch_spin_is_contended(arch_spinlock_t *lock)

static inline int arch_spin_is_contended(arch_spinlock_t *lock)

{

{

	struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets);

	struct __raw_tickets tmp = READ_ONCE(lock->tickets);





	return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC;

	return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC;

}

}