> "Stephen C. Tweedie" wrote:
>
> > Hi,
> >
> > On Wed, 14 Jul 1999 14:28:14 +0200, Sven Heursch
> > <Sven.Heursch@unibw-muenchen.de> said:
> >
> > > Could it be that the scheduler in the kernel 2.2 has problems with the
> > > priority based scheduling algorithm SCHED_FIFO and SCHED_RR. The
> > > verification was made with two concurrent running processes with the
> > > real time priorities 30 and 99. Normaly the higher one should be
> > > scheduled first. But in Linux 2.2 that do not happend evereytime.
> >
> > What test case breaks the rule for you? The scheduler's goodness
> > function should still absolutely prefer non-SCHED_OTHER processes.
>
> Yes, indeed, the kernel source code says so! But the reality is different.
> For example:
> We have two processes, A & B. A has the priority 99, B the priority 30. Both
> are the only processes which are scheduled with SCHED_FIFO in the system.
> Process A starts and goes in nanosleep(). Now B got the CPU and does for
> example the access() system call. After a few micorseconds, an interrupt is
> generated and interrupts the process B. Process A has installed an
> interrupthandler for that interrupt before and is beeing signaled by the
> ISR.
You mean it called a kernel function to install an interrupt handler,
and the handler does a send_sig() ?
> Now the crazy thing: Wheather A has the highest priority in the system and
> is now runnable, process B is being scheduled after the ISR in Kernel 2.2.
> Process A is sleeping on.
So it is never waken up, or just too late?
-Andi
-- This is like TV. I don't like TV.- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/