Documentation/locking/rt-mutex-design.rst

108            pi_waiters rbtree of a mutex owner task (described below).
301 Mutex owner and flags
304 The mutex structure contains a pointer to the owner of the mutex.  If the
305 mutex is not owned, this owner is set to NULL.  Since all architectures
341 The use of rt_mutex_cmpxchg with the flags in the owner field help optimize
394 (de)boosting (the owner of a mutex that a process is blocking on), a flag to
404 that the state of the owner and lock can change when entered into this function.
425 fails).  Only when the owner field of the mutex is NULL can the lock be
435 tree of the owner.
446 the "Has Waiters" flag of the mutex's owner field. By setting this flag
447 now, the current owner of the mutex being contended for can't release the mutex
450 forces the current owner to synchronize with this code.
454    1) The lock has no owner
459 owner of the lock, and if the lock still has waiters, the top_waiter
466 as the lock's owner's pi_waiters tree. This is described in the next
480 previous top waiter process (if it exists) from the pi_waiters of the owner,
481 and add the current process to that tree.  Since the pi_waiter of the owner
482 has changed, we call rt_mutex_adjust_prio on the owner to see if the owner
485 If the owner is also blocked on a lock, and had its pi_waiters changed
487 and run rt_mutex_adjust_prio_chain on the owner, as described earlier.
496   1) The previous lock owner released the lock, and the task now is top_waiter
519 "Has Waiters" flag of the mutex's owner, we use this to know if we need to
521 waiters, the owner field of the mutex would equal the current process and
522 the mutex can be unlocked by just replacing the owner field with NULL.
524 If the owner field has the "Has Waiters" bit set (or CMPXCHG is not available),
531 do not have CMPXCHG, this is the location that the owner of the mutex will
535 or timeout between the time the owner failed the fast path CMPXCHG check and
537 owner still needs to make this check. If there are no waiters then the mutex
538 owner field is set to NULL, the wait_lock is released and nothing more is
543 On the wake up code, the pi_lock of the current owner is taken.  The top
545 as well as the pi_waiters tree of the current owner. The "Has Waiters" bit is
548 Finally we unlock the pi_lock of the pending owner and wake it up.