Hi Anton,
timers never trigger at the same time or when in a TTimer::Notify.
Little explanation:
- there are two types of timers synchronous and a-synchronous.
- synchronous timers are only handled via the ROOT eventloop
(see TUnixSystem::DispatchOneEvent()). If there are no mouse/keyboard
events then the synchronous timer queue is checked. So if the processing
of a mouse/keyboard event takes a long time synchronous timers are not
called for a while. To prevent this from happening one can call in long
procedures gSystem->ProcessEvents(). The system schedules only the
next timer in the queue when the current one's Notify() has finished.
- a-synchronous timers are triggered via SIGALARM, i.e. the program is
interupted and execution jumps to the Notify() function. When the
notify is finished the next a-sync timer is scheduled and the system
resumes from the place where it was initially interrupted. One of the
things to remember when using a-sync timers is don't make any graphics
calls in them. X11 is not re-entrant and it might be that the SIGALARM
signal interrupted the system while being in X11. A-sync timers are best
used to set flags that you can test at a convenient and controlled
time.
Hope this helps.
Cheers, Fons.
Anton Fokin wrote:
>
> Hi there,
>
> well, I am curious what happens if one sets up two TTimer derived objects
> and FirstTimer.Notify() call comes while SecondTimer.Notify() is executing.
> I would also like to know 1. if there is any way to protect a portion of
> code in a way it is done in Java (synchronized()) 2. If I can set any
> "priorities" for timer calls. (Well, to get this discussion useful for all
> rooters let's assume that I am a lamer in Unix/whatsoever system
> programming and do not know much about system calls (semaphores, etc.)) :)
>
> Always yours,
>
> Dr. Anton Fokin
>
> Division of Cosmic and Subatomic Physics
> Lund University
> Sweden
--
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