Spinlocks and rwlocks behave differently in the try variants regarding
preemption: rwlocks are switching preemption off before testing the
lock, while spinlocks do so only after the first check.
Modify _spin_trylock() to disable preemption before testing the lock
to be held in order to be preemption-ready.
Signed-off-by: Juergen Gross <jgr...@suse.com>
---
V3:
- new patch
---
xen/common/spinlock.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/xen/common/spinlock.c b/xen/common/spinlock.c
index b4aaf6bce6..f4eb50f030 100644
--- a/xen/common/spinlock.c
+++ b/xen/common/spinlock.c
@@ -240,13 +240,16 @@ int _spin_trylock(spinlock_t *lock)
{
spinlock_tickets_t old, new;
+ preempt_disable();
check_lock(&lock->debug, true);
old = observe_lock(&lock->tickets);
if ( old.head != old.tail )
+ {
+ preempt_enable();
return 0;
+ }
new = old;
new.tail++;
- preempt_disable();
if ( cmpxchg(&lock->tickets.head_tail,
old.head_tail, new.head_tail) != old.head_tail )
{
--
2.26.2
