Copyright (c) 2005 David Xu <davidxu@FreeBSD.org> All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice(s), this list of conditions and the following disclaimer as the first lines of this file unmodified other than the possible addition of one or more copyright notices. 2. Redistributions in binary form...
NAMEtimer_create - create a per-process timer (REALTIME)
SYNOPSISIn time.h In signal.h Ft int Fo timer_create Fa clockid_t clockid struct sigevent *restrict evp Fa timer_t *restrict timerid Fc
DESCRIPTIONThe Fn timer_create system call creates a per-process timer using the specified clock, Fa clock_id , as the timing base. The Fn timer_create system call returns, in the location referenced by Fa timerid , a timer ID of type Vt timer_t used to identify the timer in timer requests. This timer ID is unique within the calling process until the timer is deleted. The particular clock, Fa clock_id , is defined in In time.h . The timer whose ID is returned is in a disarmed state upon return from Fn timer_create .
The Fa evp argument, if non- NULL points to a Vt sigevent structure. This structure, allocated by the application, defines the asynchronous notification to occur when the timer expires.
If Fa evp->sigev_notify is SIGEV_SIGNO or SIGEV_THREAD_ID the signal specified in Fa evp->sigev_signo will be sent to the calling process (SIGEV_SIGNO ) or to the thread whose LWP ID is Fa evp->sigev_notify_thread_id (SIGEV_THREAD_ID ) The information for the queued signal will include:
- Member Ta Value
- si_code Ta SI_TIMER
- si_value Ta the value stored in
- Fa evp->sigev_value
- si_timerid Ta timer ID
- si_overrun Ta timer overrun count
- si_errno Ta If timer overrun is
- Br q Dv DELAYTIMER_MAX , an error code defined in In errno.h
If the Fa evp argument is NULL the effect is as if the Fa evp argument pointed to a Vt sigevent structure with the sigev_notify member having the value SIGEV_SIGNAL the sigev_signo having a default signal number (SIGALRM ) and the sigev_value member having the value of the timer ID.
This implementation supports a Fa clock_id of CLOCK_REALTIME or CLOCK_MONOTONIC
If Fa evp->sigev_notify is SIGEV_THREAD and Fa sev->sigev_notify_attributes is not NULL if the attribute pointed to by Fa sev->sigev_notify_attributes has a thread stack address specified by a call to Fn pthread_attr_setstack or Fn pthread_attr_setstackaddr , the results are unspecified if the signal is generated more than once.
RETURN VALUESIf the call succeeds, Fn timer_create returns zero and updates the location referenced by Fa timerid to a Vt timer_t , which can be passed to the per-process timer calls. If an error occurs, the system call returns a value of -1 and the global variable errno is set to indicate the error. The value of Fa timerid is undefined if an error occurs.
ERRORSThe Fn timer_create system call will fail if:
- Bq Er EAGAIN
- The calling process has already created all of the timers it is allowed by this implementation.
- Bq Er EINVAL
- The specified clock ID is not supported.
- Bq Er EINVAL
- The specified asynchronous notification method is not supported.
- Bq Er EFAULT
- Any arguments point outside the allocated address space or there is a memory protection fault.