сон высокого разрешения с указанием часов (high-resolution sleep with specifiable clock)
Имя (Name)
clock_nanosleep - high-resolution sleep with specifiable clock
Синопсис (Synopsis)
#include <time.h>
int clock_nanosleep(clockid_t clockid, int flags,
const struct timespec *request,
struct timespec *remain);
Link with -lrt (only for glibc versions before 2.17).
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
clock_nanosleep():
_POSIX_C_SOURCE >= 200112L
Описание (Description)
Like nanosleep(2), clock_nanosleep() allows the calling thread to
sleep for an interval specified with nanosecond precision. It
differs in allowing the caller to select the clock against which
the sleep interval is to be measured, and in allowing the sleep
interval to be specified as either an absolute or a relative
value.
The time values passed to and returned by this call are specified
using timespec structures, defined as follows:
struct timespec {
time_t tv_sec; /* seconds */
long tv_nsec; /* nanoseconds [0 .. 999999999] */
};
The clockid argument specifies the clock against which the sleep
interval is to be measured. This argument can have one of the
following values:
CLOCK_REALTIME
A settable system-wide real-time clock.
CLOCK_TAI (since Linux 3.10)
A system-wide clock derived from wall-clock time but
ignoring leap seconds.
CLOCK_MONOTONIC
A nonsettable, monotonically increasing clock that
measures time since some unspecified point in the past
that does not change after system startup.
CLOCK_BOOTIME (since Linux 2.6.39)
Identical to CLOCK_MONOTONIC, except that it also includes
any time that the system is suspended.
CLOCK_PROCESS_CPUTIME_ID
A settable per-process clock that measures CPU time
consumed by all threads in the process.
See clock_getres(2) for further details on these clocks. In
addition, the CPU clock IDs returned by clock_getcpuclockid(3)
and pthread_getcpuclockid(3) can also be passed in clockid.
If flags is 0, then the value specified in request is interpreted
as an interval relative to the current value of the clock
specified by clockid.
If flags is TIMER_ABSTIME, then request is interpreted as an
absolute time as measured by the clock, clockid. If request is
less than or equal to the current value of the clock, then
clock_nanosleep() returns immediately without suspending the
calling thread.
clock_nanosleep() suspends the execution of the calling thread
until either at least the time specified by request has elapsed,
or a signal is delivered that causes a signal handler to be
called or that terminates the process.
If the call is interrupted by a signal handler, clock_nanosleep()
fails with the error EINTR. In addition, if remain is not NULL,
and flags was not TIMER_ABSTIME, it returns the remaining unslept
time in remain. This value can then be used to call
clock_nanosleep() again and complete a (relative) sleep.
Возвращаемое значение (Return value)
On successfully sleeping for the requested interval,
clock_nanosleep() returns 0. If the call is interrupted by a
signal handler or encounters an error, then it returns one of the
positive error number listed in ERRORS.
Ошибки (Error)
EFAULT request or remain specified an invalid address.
EINTR The sleep was interrupted by a signal handler; see
signal(7).
EINVAL The value in the tv_nsec field was not in the range 0 to
999999999 or tv_sec was negative.
EINVAL clockid was invalid. (CLOCK_THREAD_CPUTIME_ID is not a
permitted value for clockid.)
ENOTSUP
The kernel does not support sleeping against this clockid.
Версии (Versions)
The clock_nanosleep() system call first appeared in Linux 2.6.
Support is available in glibc since version 2.1.
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008.
Примечание (Note)
If the interval specified in request is not an exact multiple of
the granularity underlying clock (see time(7)), then the interval
will be rounded up to the next multiple. Furthermore, after the
sleep completes, there may still be a delay before the CPU
becomes free to once again execute the calling thread.
Using an absolute timer is useful for preventing timer drift
problems of the type described in nanosleep(2). (Such problems
are exacerbated in programs that try to restart a relative sleep
that is repeatedly interrupted by signals.) To perform a
relative sleep that avoids these problems, call clock_gettime(2)
for the desired clock, add the desired interval to the returned
time value, and then call clock_nanosleep() with the
TIMER_ABSTIME flag.
clock_nanosleep() is never restarted after being interrupted by a
signal handler, regardless of the use of the sigaction(2)
SA_RESTART flag.
The remain argument is unused, and unnecessary, when flags is
TIMER_ABSTIME. (An absolute sleep can be restarted using the
same request argument.)
POSIX.1 specifies that clock_nanosleep() has no effect on signals
dispositions or the signal mask.
POSIX.1 specifies that after changing the value of the
CLOCK_REALTIME clock via clock_settime(2), the new clock value
shall be used to determine the time at which a thread blocked on
an absolute clock_nanosleep() will wake up; if the new clock
value falls past the end of the sleep interval, then the
clock_nanosleep() call will return immediately.
POSIX.1 specifies that changing the value of the CLOCK_REALTIME
clock via clock_settime(2) shall have no effect on a thread that
is blocked on a relative clock_nanosleep().
Смотри также (See also)
clock_getres(2), nanosleep(2), restart_syscall(2),
timer_create(2), sleep(3), usleep(3), time(7)
