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Full Discussion: signal handling question
Top Forums Programming signal handling question Post 302199772 by fox_hound_33 on Tuesday 27th of May 2008 10:43:15 PM
Old 05-27-2008
I get what you guys mean.

I ran some test code using usleep and found some interesting results.
When i put usleep to 0.1secs, the actual sleeping time varies from the set point (0.1secs) with an error of about +5%. The same error percentage jumps to about +40% when i put usleep to 0.01sec and the same error jumps to about +300%(!!!!) when i put usleep to 0.001sec.

Looks like as the timer resolution is brought down the error keeps increasing. Could be due to system timer resolution as mentioned as well as the priority based scheduling employed by linux.

Anyway thanks a lot guys.
 

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LEARN ABOUT OPENSOLARIS

alarm

alarm(2)							   System Calls 							  alarm(2)

NAME

       alarm - schedule an alarm signal

SYNOPSIS

       #include <unistd.h>

       unsigned int alarm(unsigned int seconds);

DESCRIPTION

       The alarm() function causes the system to generate a SIGALRM signal for the process after the number of real-time seconds specified by sec-
       onds  have  elapsed (see  signal.h(3HEAD)). Processor scheduling delays may prevent the process from handling the signal as soon as  it	is
       generated.

       If  seconds  is	0,  a  pending	alarm  request,  if  any, is cancelled. If seconds is greater than LONG_MAX/hz, seconds is rounded down to
       LONG_MAX/hz. The value of hz is normally 100.

       Alarm requests are not stacked; only one SIGALRM  generation can  be  scheduled in this manner; if the SIGALRM signal has not yet been gen-
       erated, the call will result in rescheduling the time at which the SIGALRM signal will be generated.

       The  fork(2)  function clears pending alarms in the child process. A new process image created by one of the exec(2) functions inherits the
       time left to an alarm signal in the old process's image.

RETURN VALUES

       If there is a previous alarm request with time  remaining, alarm() returns  a  non-zero	value  that  is the number of  seconds	until  the
       previous request would  have  generated	a SIGALRM signal.  Otherwise, alarm() returns 0.

ERRORS

       The alarm() function is always successful; no return value is reserved to indicate an error.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       exec(2), fork(2), signal.h(3HEAD), attributes(5), standards(5)

SunOS 5.11							    6 Jun 2007								  alarm(2)
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