FUTEX_WAIT_REQUEUE_P(9) Futex API reference FUTEX_WAIT_REQUEUE_P(9)NAMEfutex_wait_requeue_pi - Wait on uaddr and take uaddr2
SYNOPSIS
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
DESCRIPTION
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
AUTHOR
Rusty Russell <rusty@rustcorp.com.au>
Author.
COPYRIGHTKernel Hackers Manual 3.11 November 2013 FUTEX_WAIT_REQUEUE_P(9)
