Interval timers on Fedora

[Douglas Phillipson]

John Wendel wrote:
> Douglas Phillipson wrote:
>> This probably isn't a Fedora specific question so I apologize if this 
>> is the wrong forum.
>>
>> Anybody know if you can set more than one interval timer in a single 
>> process?
>>
>> (setitimer())
>>
>> Would starting more than one interval timer in a single process 
>> confuse the signal system when delivering the SIGALRM to the receiving 
>> process?
>>
>> In other words, can I have a 10 second interval timer which when times 
>> out delivers a sigalrm to one function, and in the same process have a 
>> 1 second interval timer set to give a sigalrm to another function?
>>
>> I'm having trouble with a second interval timer, it doesn't seem to 
>> work, or deliver the signal to the desired function.  I'm using a 
>> separate instance of struct itimerval and struct sigaction when 
>> setting up the timers.  I have several books on the subject of 
>> interval timers but none say you shouldn't do this, just "Every 
>> process has its own set of timers".  But they might be referring to 
>> REAL, VIRTUAL, and PROF timers, a single set of these for each process.
>>
>> Opinions requested...
>>
>> Thanks
>>
>> Doug P
>>
> 
> I'm not an expert on this stuff, but my understanding is that setitimer 
> gives your process access to one of three predefined timers (REAL, 
> VIRTUAL, and PROF) and only the REAL timer is actually useful.
> So your second call to setitimer is mucking up the settings from the 
> first call.
> 
> See "man timer_create" for the POSIX timer stuff that lets you have lots 
> of timers.
> 
> I recommend the O'REILLY book POSIX 4 by Bill Gallmeister for a good 
> explanation of this fairly complicated topic.
> 
> Regards,
> 
> John
> 

My result on the timer issue is that a interval timer won't call its 
timeout function while msgrcv() is waiting for a message on a queue.

Regards

Doug P