illumos: manual page: pthread_rwlock

PTHREAD_RWLOCK_TIMEDRDLOCK(3C) Standard C Library Functions

NAME

pthread_rwlock_timedrdlock, pthread_rwlock_reltimedrdlock_np - lock a
read-write lock for reading

SYNOPSIS

cc -mt [ flag... ] file... [ library... ]
#include <pthread.h>
#include <time.h>

int pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict rwlock,
const struct timespec *restrict abs_timeout);

int pthread_rwlock_reltimedrdlock_np(pthread_rwlock_t *restrict rwlock,
const struct timespec *restrict rel_timeout);

DESCRIPTION

The pthread_rwlock_timedrdlock() function applies a read lock to the
read-write lock referenced by rwlock as in the pthread_rwlock_rdlock(3C)
function. If the lock cannot be acquired without waiting for other
threads to unlock the lock, this wait will be terminated when the
specified timeout expires. The timeout expires when the absolute time
specified by abs_timeout passes, as measured by the CLOCK_REALTIME clock
(that is, when the value of that clock equals or exceeds abs_timeout), or
if the absolute time specified by abs_timeout has already been passed at
the time of the call.

The pthread_rwlock_reltimedrdlock_np() function is identical to the
pthread_rwlock_timedrdlock() function, except that the timeout is
specified as a relative time interval. The timeout expires when the time
interval specified by rel_timeout passes, as measured by the
CLOCK_REALTIME clock, or if the time interval specified by rel_timeout is
negative at the time of the call.

The resolution of the timeout is the resolution of the CLOCK_REALTIME
clock. The timespec data type is defined in the <time.h> header. Under
no circumstances does either function fail with a timeout if the lock can
be acquired immediately. The validity of the timeout parameter need not
be checked if the lock can be immediately acquired.

If a signal that causes a signal handler to be executed is delivered to a
thread blocked on a read-write lock with a call to
pthread_rwlock_timedrdlock() or pthread_rwlock_reltimedrdlock_np(), upon
return from the signal handler the thread resumes waiting for the lock as
if it was not interrupted.

The calling thread might deadlock if at the time the call is made it
holds a write lock on rwlock.

The results are undefined if this function is called with an
uninitialized read-write lock.

RETURN VALUES

The pthread_rwlock_timedrdlock() and pthread_rwlock_reltimedrdlock_np()
functions return 0 if the lock for reading on the read-write lock object
referenced by rwlock is acquired. Otherwise, an error number is returned
to indicate the error.

ERRORS

The pthread_rwlock_timedrdlock() and pthread_rwlock_reltimedrdlock_np()
functions will fail if:

ETIMEDOUT
The lock could not be acquired before the specified timeout
expired.

The pthread_rwlock_timedrdlock() and pthread_rwlock_reltimedrdlock_np()
functions may fail if:

EAGAIN
The read lock could not be acquired because the maximum number
of read locks for lock would be exceeded.

EDEADLK
The calling thread already holds a write lock on rwlock.

EINVAL
The value specified by rwlock does not refer to an initialized
read-write lock object, or the timeout nanosecond value is
less than zero or greater than or equal to 1 000 million.

ATTRIBUTES