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   timerfd_settime    ( 2 )

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Примечание (Note)

Suppose the following scenario for CLOCK_REALTIME or CLOCK_REALTIME_ALARM timer that was created with timerfd_create():

(a) The timer has been started (timerfd_settime()) with the TFD_TIMER_ABSTIME and TFD_TIMER_CANCEL_ON_SET flags;

(b) A discontinuous change (e.g., settimeofday(2)) is subsequently made to the CLOCK_REALTIME clock; and

(c) the caller once more calls timerfd_settime() to rearm the timer (without first doing a read(2) on the file descriptor).

In this case the following occurs:

• The timerfd_settime() returns -1 with errno set to ECANCELED. (This enables the caller to know that the previous timer was affected by a discontinuous change to the clock.)

• The timer is successfully rearmed with the settings provided in the second timerfd_settime() call. (This was probably an implementation accident, but won't be fixed now, in case there are applications that depend on this behaviour.)