Movatterモバイル変換

TIMER_GETOVERRUN(2)        Linux Programmer's ManualTIMER_GETOVERRUN(2)NAME       timer_getoverrun - get overrun count for a POSIX per-process timerSYNOPSIS       #include <time.h>       int timer_getoverrun(timer_t timerid);       Link with -lrt.   Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):       timer_getoverrun(): _POSIX_C_SOURCE >= 199309LDESCRIPTION       timer_getoverrun()  returns  the "overrun count" for the timer referred       to by timerid.  An application can use the overrun count to  accurately       calculate the number of timer expirations that would have occurred over       a given time interval.  Timer overruns can occur  both  when  receiving       expiration  notifications  via  signals (SIGEV_SIGNAL), and via threads       (SIGEV_THREAD).       When expiration notifications are delivered via a signal, overruns  can       occur  as  follows.  Regardless of whether or not a real-time signal is       used for timer notifications, the system queues at most one signal  per       timer.   (This  is the behavior specified by POSIX.1.  The alternative,       queuing one signal for each timer expiration, could  easily  result  in       overflowing  the allowed limits for queued signals on the system.)  Be-       cause of system scheduling delays, or because the signal may be  tempo-       rarily  blocked, there can be a delay between the time when the notifi-       cation signal is generated and the time when  it  is  delivered  (e.g.,       caught  by  a signal handler) or accepted (e.g., usingsigwaitinfo(2)).       In this interval, further timer expirations may occur.  The timer over-       run  count  is the number of additional timer expirations that occurred       between the time when the signal was generated and when it  was  deliv-       ered or accepted.       Timer  overruns can also occur when expiration notifications are deliv-       ered via invocation of a thread, since there may be an arbitrary  delay       between  an expiration of the timer and the invocation of the notifica-       tion thread, and in that delay interval, additional  timer  expirations       may occur.RETURN VALUE       On  success, timer_getoverrun() returns the overrun count of the speci-       fied timer; this count may be 0 if no overruns have occurred.  On fail-       ure, -1 is returned, and errno is set to indicate the error.ERRORS       EINVAL timerid is not a valid timer ID.VERSIONS       This system call is available since Linux 2.6.CONFORMING TO       POSIX.1-2001, POSIX.1-2008.NOTES       When  timer  notifications are delivered via signals (SIGEV_SIGNAL), on       Linux it is also possible to obtain the overrun count via the  si_over-       run  field  of the siginfo_t structure (seesigaction(2)).  This allows       an application to avoid the overhead of making a system call to  obtain       the overrun count, but is a nonportable extension to POSIX.1.       POSIX.1 discusses timer overruns only in the context of timer notifica-       tions using signals.BUGS       POSIX.1 specifies that if the  timer  overrun  count  is  equal  to  or       greater  than  an  implementation-defined maximum, DELAYTIMER_MAX, then       timer_getoverrun() should return DELAYTIMER_MAX.  However,  Linux  does       not implement this feature: instead, if the timer overrun value exceeds       the maximum representable integer, the counter  cycles,  starting  once       more from low values.EXAMPLE       Seetimer_create(2).SEE ALSOclock_gettime(2),sigaction(2),signalfd(2),sigwaitinfo(2), timer_cre-ate(2),timer_delete(2),timer_settime(2),signal(7),time(7)COLOPHON       This page is part of release 5.05 of the Linux  man-pages  project.   A       description  of  the project, information about reporting bugs, and the       latest    version    of    this    page,    can     be     found     at       https://www.kernel.org/doc/man-pages/.Linux                             2017-09-15TIMER_GETOVERRUN(2)