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SubjectRe: [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U8
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On Wed, 2004-10-20 at 10:18, Ingo Molnar wrote:
> note that the keyboard and USB interrupts are SCHED_OTHER by default, so
> they could be delayed quite long depending on the workload.

Why is this the default behavior? It seems like you would want all IRQ
threads to be SCHED_FIFO by default. Otherwise it seems like the
scheduler could decide to run a normal userspace process (like, say, X)
while an IRQ thread is runnable.

Is it really a good idea for IRQ threads to be subject to the whims of
the scheduler?

Also, on modern machines, this would effectively make all IRQ threads
SCHED_OTHER because the USB port shares an interrupt with everything:

0: 36676353 XT-PIC timer 0/76353
1: 8759 XT-PIC i8042 5/8759
2: 0 XT-PIC cascade 0/0
8: 4 XT-PIC rtc 0/4
10: 0 XT-PIC uhci_hcd 0/0
11: 210713 XT-PIC uhci_hcd, eth0 0/10713
12: 0 XT-PIC uhci_hcd 0/0
15: 79277 XT-PIC ide1 0/79276
NMI: 0
ERR: 0

Lee


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