![]() The second signal in such an event will be lost. ITIMER_REAL timer may expire before the signal from a previous expiration has beenĭelivered. Signals listed above may be pending for a process. The generation and delivery of a signal are distinct, and only one instance of each of the Don't use this Linux misfeature: it is nonportable In Linux, this is treated as being equivalent to a call in which the new_value fields are Many systems (Solaris, the BSDs, and perhaps others) treat this as equivalent to: The standards are silent on the meaning of the call: POSIX.1 leaves the interaction between setitimer() and the three interfaces alarm(2), Timers are preserved across an execve(2). ( timer_gettime(2), timer_settime(2), etc.) instead.Ī child created via fork(2) does not inherit its parent's interval timers. Getitimer() and setitimer() obsolete, recommending the use of the POSIX timers API POSIX.1-2001, SVr4, 4.4BSD (this call first appeared in 4.2BSD). On error, -1 is returned, and errno is set appropriately.ĮRRORS EFAULT new_value, old_value, or curr_value is not valid a pointer.ĮINVAL which is not one of ITIMER_REAL, ITIMER_VIRTUAL, or ITIMER_PROF or (since LinuxĢ.6.22) one of the tv_usec fields in the structure pointed to by new_value contains Offset by a small time dependent on the system loading. The signal will be delivered immediately when generated. If the timer expires while the process is active (always true for ITIMER_VIRTUAL), (But see BUGS below.) Upon expiration, a signal will be generated and the timer Timers will never expire before the requested time, but may expire some (short) timeĪfterward, which depends on the system timer resolution and on the system load see Timer which is set to zero ( it_value is zero or the timer expires and it_interval is zero)īoth tv_sec and tv_usec are significant in determining the duration of a timer. Timers decrement from it_value to zero, generate a signal, and reset to it_interval. Is non-NULL, the old value of the timer (i.e., the same information as returned by The function setitimer() sets the specified timer to the value in new_value. Of zero returned in (both subfields of) this field indicates that this is a single-shot ![]() The it_interval field is set to the timer interval (period) a value The field it_value are set to the amount of time remaining on the timer, or zero if the Specified by which (one of ITIMER_REAL, ITIMER_VIRTUAL, or ITIMER_PROF). Value (i.e., the amount of time remaining until the next expiration) of the timer The function getitimer() fills the structure pointed to by curr_value with the current Struct timeval it_value /* Time until next expiration */ ![]() Struct timeval it_interval /* Interval for periodic timer */ Timer values are defined by the following structures: Usually used to profile the time spent by the application in user and Coupled with ITIMER_VIRTUAL, this timer is ITIMER_PROF decrements both when the process executes and when the system is executing ITIMER_VIRTUAL decrements only when the process is executing, and delivers SIGVTALRM upon ITIMER_REAL decrements in real time, and delivers SIGALRM upon expiration. Timer is reset to the specified interval (if nonzero). When a timer expires, a signal is sent to the process, and the The system provides each process with three interval timers, each decrementing in aĭistinct time domain. SYNOPSIS #include int getitimer(int which, struct itimerval * curr_value ) int setitimer(int which, const struct itimerval * new_value, struct itimerval * old_value ) DESCRIPTION SPDX-License-Identifier: GPL-2.0 /* * linux/kernel/itimer.Getitimer, setitimer - get or set value of an interval timer
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