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    Subject[patch 17/63] locking/rtmutex: Add wake_state to rt_mutex_waiter
    From: Thomas Gleixner <tglx@linutronix.de>

    Regular sleeping locks like mutexes, rtmutexes and rw_semaphores are always
    entering and leaving a blocking section with task state == TASK_RUNNING.

    On a non-RT kernel spinlocks and rwlocks never affect the task state, but
    on RT kernels these locks are converted to rtmutex based 'sleeping' locks.

    So in case of contention the task goes to block which requires to carefully
    preserve the task state and restore it after acquiring the lock taking
    regular wakeups for the task into account which happened while the task was
    blocked. This state preserving is achieved by having a seperate task state
    for blocking on a RT spin/rwlock and a saved_state field in task_struct
    along with careful handling of these wakeup scenarios in try_to_wake_up().

    To avoid conditionals in the rtmutex code, store the wake state which has
    to be used for waking a lock waiter in rt_mutex_waiter which allows to
    handle the regular and RT spin/rwlocks by handing it to wake_up_state().

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    V2: Use unsigned int for wake_state (Peter Z.)
    ---
    kernel/locking/rtmutex.c | 2 +-
    kernel/locking/rtmutex_common.h | 9 +++++++++
    2 files changed, 10 insertions(+), 1 deletion(-)
    ---
    --- a/kernel/locking/rtmutex.c
    +++ b/kernel/locking/rtmutex.c
    @@ -692,7 +692,7 @@ static int __sched rt_mutex_adjust_prio_
    * to get the lock.
    */
    if (prerequeue_top_waiter != rt_mutex_top_waiter(lock))
    - wake_up_process(rt_mutex_top_waiter(lock)->task);
    + wake_up_state(waiter->task, waiter->wake_state);
    raw_spin_unlock_irq(&lock->wait_lock);
    return 0;
    }
    --- a/kernel/locking/rtmutex_common.h
    +++ b/kernel/locking/rtmutex_common.h
    @@ -25,6 +25,7 @@
    * @pi_tree_entry: pi node to enqueue into the mutex owner waiters tree
    * @task: task reference to the blocked task
    * @lock: Pointer to the rt_mutex on which the waiter blocks
    + * @wake_state: Wakeup state to use (TASK_NORMAL or TASK_RTLOCK_WAIT)
    * @prio: Priority of the waiter
    * @deadline: Deadline of the waiter if applicable
    */
    @@ -33,6 +34,7 @@ struct rt_mutex_waiter {
    struct rb_node pi_tree_entry;
    struct task_struct *task;
    struct rt_mutex_base *lock;
    + unsigned int wake_state;
    int prio;
    u64 deadline;
    };
    @@ -158,9 +160,16 @@ static inline void rt_mutex_init_waiter(
    debug_rt_mutex_init_waiter(waiter);
    RB_CLEAR_NODE(&waiter->pi_tree_entry);
    RB_CLEAR_NODE(&waiter->tree_entry);
    + waiter->wake_state = TASK_NORMAL;
    waiter->task = NULL;
    }

    +static inline void rtlock_init_rtmutex_waiter(struct rt_mutex_waiter *waiter)
    +{
    + rt_mutex_init_waiter(waiter);
    + waiter->wake_state = TASK_RTLOCK_WAIT;
    +}
    +
    #else /* CONFIG_RT_MUTEXES */
    /* Used in rcu/tree_plugin.h */
    static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
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