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Full Discussion: signal handling question
Top Forums Programming signal handling question Post 302199631 by jim mcnamara on Tuesday 27th of May 2008 10:17:03 AM
Old 05-27-2008
andryk is right - alarm timer expiry (SIGALRM) will be delivered to the process, but only when the process has enough priority to be awakened. In other words, if you ask for 10ms sleep time on a busy system, your alarm will be instantiated after 10ms, guaranteed, but the time when your process gets a turn at the CPU is NOT guaranteed, unless your process has elevated (realtime) priority. You have to wait for other processes to give up the CPU before you get it back, and process the signal. This becomes a problem on a busy system, or when the duration of the wait is less than a quantum slice and there is a least one other process that needs the cpu.

I really don't recommend it, but on a busy system you may have to nice your program up to a very high prioity to get the results you asked for.
 

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LEARN ABOUT CENTOS

alarm

ALARM(2)						     Linux Programmer's Manual							  ALARM(2)

NAME

       alarm - set an alarm clock for delivery of a signal

SYNOPSIS

       #include <unistd.h>

       unsigned int alarm(unsigned int seconds);

DESCRIPTION

       alarm() arranges for a SIGALRM signal to be delivered to the calling process in seconds seconds.

       If seconds is zero, any pending alarm is canceled.

       In any event any previously set alarm() is canceled.

RETURN VALUE

       alarm()	returns the number of seconds remaining until any previously scheduled alarm was due to be delivered, or zero if there was no pre-
       viously scheduled alarm.

CONFORMING TO

       SVr4, POSIX.1-2001, 4.3BSD.

NOTES

       alarm() and setitimer(2) share the same timer; calls to one will interfere with use of the other.

       sleep(3) may be implemented using SIGALRM; mixing calls to alarm() and sleep(3) is a bad idea.

       Scheduling delays can, as ever, cause the execution of the process to be delayed by an arbitrary amount of time.

SEE ALSO

       gettimeofday(2), pause(2), select(2), setitimer(2), sigaction(2), signal(2), sleep(3), time(7)

COLOPHON

       This page is part of release 3.53 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2013-04-18								  ALARM(2)
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