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Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull locking fixes from Ingo Molnar:
 "Two fixes: the paravirt spin_unlock() corruption/crash fix, and an
  rtmutex NULL dereference crash fix"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/spinlocks/paravirt: Fix memory corruption on unlock
  locking/rtmutex: Avoid a NULL pointer dereference on deadlock
This commit is contained in:
Linus Torvalds
2015-02-21 10:45:03 -08:00
parent 5fbe4c224c d6abfdb202
commit 10436cf881
4 changed files with 64 additions and 55 deletions
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13
arch/x86/kernel/kvm.c
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@@ -609,7 +609,7 @@ static inline void check_zero(void)
u8 ret;
u8 old;
old = ACCESS_ONCE(zero_stats);
old = READ_ONCE(zero_stats);
if (unlikely(old)) {
ret = cmpxchg(&zero_stats, old, 0);
/* This ensures only one fellow resets the stat */
@@ -727,6 +727,7 @@ __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
int cpu;
u64 start;
unsigned long flags;
__ticket_t head;
if (in_nmi())
return;
@@ -768,11 +769,15 @@ __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
*/
__ticket_enter_slowpath(lock);
/* make sure enter_slowpath, which is atomic does not cross the read */
smp_mb__after_atomic();
/*
* check again make sure it didn't become free while
* we weren't looking.
*/
if (ACCESS_ONCE(lock->tickets.head) == want) {
head = READ_ONCE(lock->tickets.head);
if (__tickets_equal(head, want)) {
add_stats(TAKEN_SLOW_PICKUP, 1);
goto out;
}
@@ -803,8 +808,8 @@ static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
add_stats(RELEASED_SLOW, 1);
for_each_cpu(cpu, &waiting_cpus) {
const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu);
if (ACCESS_ONCE(w->lock) == lock &&
ACCESS_ONCE(w->want) == ticket) {
if (READ_ONCE(w->lock) == lock &&
READ_ONCE(w->want) == ticket) {
add_stats(RELEASED_SLOW_KICKED, 1);
kvm_kick_cpu(cpu);
break;