futex_wait_requeue_pi — Wait on uaddr and take uaddr2
|u32 __user * uaddr,|
|unsigned int flags,|
|ktime_t * abs_time,|
|u32 __user * uaddr2|
the futex we initially wait on (non-pi)
futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be the same type, no requeueing from private to shared, etc.
the expected value of uaddr
32 bit wakeup bitset set by userspace, defaults to all
the pi futex we will take prior to returning to user-space
The caller will wait on uaddr and will be requeued by
uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake
on uaddr2 and complete the acquisition of the rt_mutex prior to returning to
userspace. This ensures the rt_mutex maintains an owner when it has waiters;
without one, the pi logic would not know which task to boost/deboost, if
there was a need to.
We call schedule in
futex_wait_queue_me when we enqueue and return there
via the following--
1) wakeup on uaddr2 after an atomic lock acquisition by
2) wakeup on uaddr2 after a requeue
If 3, cleanup and return -ERESTARTNOINTR.
If 2, we may then block on trying to take the rt_mutex and return via: 5) successful lock 6) signal 7) timeout 8) other lock acquisition failure
If 6, return -EWOULDBLOCK (restarting the syscall would do the same).
If 4 or 7, we cleanup and return with -ETIMEDOUT.