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Timer interrupts

To: linux-mips@linux-mips.org
Subject: Timer interrupts
From: madprops@gmx.net
Date: Fri, 16 Dec 2005 16:34:36 +0100 (MET)
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
Hi,

i'm using CP0_Count/CP0_Compare to get timer interrupts. They should be
turned off while being in kernel mode (performing syscalls / handling
tlb-misses etc) and enabled in user mode. 

Whenever a timer interrupt happens in kernel mode, the exception should be
delayed until it is switched back to the user. Up to now I set
CP0_Status(IE) to zero when entering the kernel. Does this allow pending
interrupts or are incoming interrupts totally ignored then ??

The problem that might arise (in the second case) is that CP0_Count reaches
and passes CP0_Compare while interrupts are turned off. Back in user mode,
the running user process would get an unacceptable excessive time slice.

Thanks,

Thomas





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