other versions
FUTEX_WAIT_REQUEUE_P(9) | Futex API reference | FUTEX_WAIT_REQUEUE_P(9) |
NAME¶
futex_wait_requeue_pi - Wait on uaddr and take uaddr2SYNOPSIS¶
int
futex_wait_requeue_pi(u32 __user * uaddr,
unsigned int flags, u32 val,
ktime_t * abs_time,
u32 bitset,
u32 __user * uaddr2);
ARGUMENTS¶
uaddrthe 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 errorAUTHOR¶
Rusty Russell <rusty@rustcorp.com.au>Author.
COPYRIGHT¶
January 2017 | Kernel Hackers Manual 4.8. |