Messages in this thread | | | Date | Thu, 4 Jul 2002 11:10:16 -0500 (CDT) | From | Xinwen - Fu <> | Subject | Re: kernel timers vs network card interrupt |
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In fact I want a timer (either in user level or kernel level). This timer (hope it is a periodic timer) must expire at the interval that I specify. For example, if I want that the timer expires at 10ms, it should never be fired at 10.0000000001ms or 9.9999999999ms. That is the key part that I want!
Have an idea?
Thanks!
Xinwen Fu
On Thu, 4 Jul 2002, george anzinger wrote:
> "Richard B. Johnson" wrote: > > > > On Wed, 3 Jul 2002, Xinwen - Fu wrote: > > > > > Hi, all, > > > I'm curious that if a network card interrupt happens at the same > > > time as the kernel timer expires, what will happen? > > > > > > It's said the kernel timer is guaranteed accurate. But if > > > interrupts are not masked off, the network interrupt also should get > > > response when a kernel timer expires. So I don't know who will preempt > > > who. > > > > > > Thanks for information! > > > > > > Xinwen Fu > > > > The highest priority interrupt will get serviced first. It's the timer. > > Interrupts are serviced in priority-order. Hardware "remembers" which > > ones are pending so none are lost if some driver doesn't do something > > stupid. > > That is true as far as it goes, HOWEVER, timers are serviced > by bottom half code which is run at the end of the > interrupt, WITH THE INTERRUPT SYSTEM ON. Therefore, timer > servicing can be interrupted by an interrupt and thus be > delayed. > > -- > George Anzinger george@mvista.com > High-res-timers: > http://sourceforge.net/projects/high-res-timers/ > Real time sched: http://sourceforge.net/projects/rtsched/ > Preemption patch: > http://www.kernel.org/pub/linux/kernel/people/rml >
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