futex_wait_requeue_pi9
Wait on uaddr and take uaddr2
Usage
int futex_wait_requeue_pi(u32 __user * uaddr, unsigned int flags, u32 val, ktime_t * abs_time, u32 bitset, u32 __user * uaddr2);
Arguments
uaddr
the futex we initially wait on (non-pi)
flags
futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be the same type, no requeueing from private to shared, etc.
val
the expected value of uaddr
abs_time
absolute timeout
bitset
32 bit wakeup bitset set by userspace, defaults to all
uaddr2
the pi futex we will take prior to returning to user-space
Overview
The caller will wait on uaddr and will be requeued by futex_requeue to 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 futex_requeue 2) wakeup on uaddr2 after a requeue 3) signal 4) timeout
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.
Return
0 - On success; <0 - On error
Releases
2 releases since Debian 8 (Jessie); the text changed 1 time.