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Date: Tue, 12 May 2009 09:34:17 +1000
From: Paul Mackerras <paulus@samba.org>
To: "Chris Friesen" <cfriesen@nortel.com>
Subject: Re: question about softirqs
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Cc: linuxppc-dev@ozlabs.org, David Miller <davem@davemloft.net>
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Chris Friesen writes:

> Suppose I have a SCHED_FIFO task spinning on recvmsg() with MSG_DONTWAIT
> set (and maybe doing other stuff if there are no messages). In this
> case, schedule() would re-run the spinning task rather than running
> ksoftirqd. This could prevent any incoming packets from actually being
> sent up the stack until we get a real hardware interrupt--which could be
> a whole jiffy if interrupt mitigation is enabled in the net device.

I suggest you ask Ingo Molnar about that.

> (And maybe longer if NOHZ is enabled.)

We still have a timer interrupt every jiffy when stuff is running; we
only turn off the timer interrupts when idle.

Paul.