diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/locking/rtmutex.c | 5 | ||||
| -rw-r--r-- | kernel/locking/rtmutex_common.h | 13 |
2 files changed, 16 insertions, 2 deletions
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 8aaa352d0c17..b3c09611ef6a 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1329,8 +1329,9 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock, * for CONFIG_PREEMPT_RCU=y) * - the VCPU on which owner runs is preempted */ - if (!owner->on_cpu || waiter != rt_mutex_top_waiter(lock) || - need_resched() || vcpu_is_preempted(task_cpu(owner))) { + if (!owner->on_cpu || need_resched() || + rt_mutex_waiter_is_top_waiter(lock, waiter) || + vcpu_is_preempted(task_cpu(owner))) { res = false; break; } diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index 61256de5bd66..c47e8361bfb5 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -95,6 +95,19 @@ static inline int rt_mutex_has_waiters(struct rt_mutex_base *lock) return !RB_EMPTY_ROOT(&lock->waiters.rb_root); } +/* + * Lockless speculative check whether @waiter is still the top waiter on + * @lock. This is solely comparing pointers and not derefencing the + * leftmost entry which might be about to vanish. + */ +static inline bool rt_mutex_waiter_is_top_waiter(struct rt_mutex_base *lock, + struct rt_mutex_waiter *waiter) +{ + struct rb_node *leftmost = rb_first_cached(&lock->waiters); + + return rb_entry(leftmost, struct rt_mutex_waiter, tree_entry) == waiter; +} + static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex_base *lock) { struct rb_node *leftmost = rb_first_cached(&lock->waiters); |