diff options
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/core.c | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 961991e06337..e407c6ac4a26 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3566,14 +3566,47 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) * * The caller holds p::pi_lock if p != current or has preemption * disabled when p == current. + * + * The rules of PREEMPT_RT saved_state: + * + * The related locking code always holds p::pi_lock when updating + * p::saved_state, which means the code is fully serialized in both cases. + * + * The lock wait and lock wakeups happen via TASK_RTLOCK_WAIT. No other + * bits set. This allows to distinguish all wakeup scenarios. */ static __always_inline bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success) { + if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) { + WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) && + state != TASK_RTLOCK_WAIT); + } + if (READ_ONCE(p->__state) & state) { *success = 1; return true; } + +#ifdef CONFIG_PREEMPT_RT + /* + * Saved state preserves the task state across blocking on + * an RT lock. If the state matches, set p::saved_state to + * TASK_RUNNING, but do not wake the task because it waits + * for a lock wakeup. Also indicate success because from + * the regular waker's point of view this has succeeded. + * + * After acquiring the lock the task will restore p::__state + * from p::saved_state which ensures that the regular + * wakeup is not lost. The restore will also set + * p::saved_state to TASK_RUNNING so any further tests will + * not result in false positives vs. @success + */ + if (p->saved_state & state) { + p->saved_state = TASK_RUNNING; + *success = 1; + } +#endif return false; } |