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Diffstat (limited to 'arch/x86/xen/spinlock.c')
-rw-r--r--arch/x86/xen/spinlock.c28
1 files changed, 18 insertions, 10 deletions
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 5601506f2dd..36a5141108d 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -187,7 +187,6 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock, bool irq_enabl
struct xen_spinlock *prev;
int irq = __get_cpu_var(lock_kicker_irq);
int ret;
- unsigned long flags;
u64 start;
/* If kicker interrupts not initialized yet, just spin */
@@ -199,16 +198,12 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock, bool irq_enabl
/* announce we're spinning */
prev = spinning_lock(xl);
- flags = __raw_local_save_flags();
- if (irq_enable) {
- ADD_STATS(taken_slow_irqenable, 1);
- raw_local_irq_enable();
- }
-
ADD_STATS(taken_slow, 1);
ADD_STATS(taken_slow_nested, prev != NULL);
do {
+ unsigned long flags;
+
/* clear pending */
xen_clear_irq_pending(irq);
@@ -228,6 +223,12 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock, bool irq_enabl
goto out;
}
+ flags = __raw_local_save_flags();
+ if (irq_enable) {
+ ADD_STATS(taken_slow_irqenable, 1);
+ raw_local_irq_enable();
+ }
+
/*
* Block until irq becomes pending. If we're
* interrupted at this point (after the trylock but
@@ -238,13 +239,15 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock, bool irq_enabl
* pending.
*/
xen_poll_irq(irq);
+
+ raw_local_irq_restore(flags);
+
ADD_STATS(taken_slow_spurious, !xen_test_irq_pending(irq));
} while (!xen_test_irq_pending(irq)); /* check for spurious wakeups */
kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));
out:
- raw_local_irq_restore(flags);
unspinning_lock(xl, prev);
spin_time_accum_blocked(start);
@@ -323,8 +326,13 @@ static void xen_spin_unlock(struct raw_spinlock *lock)
smp_wmb(); /* make sure no writes get moved after unlock */
xl->lock = 0; /* release lock */
- /* make sure unlock happens before kick */
- barrier();
+ /*
+ * Make sure unlock happens before checking for waiting
+ * spinners. We need a strong barrier to enforce the
+ * write-read ordering to different memory locations, as the
+ * CPU makes no implied guarantees about their ordering.
+ */
+ mb();
if (unlikely(xl->spinners))
xen_spin_unlock_slow(xl);