From: "Chris Friesen" <cfriesen@nortel•com>
To: David Miller <davem@davemloft•net>
Cc: linuxppc-dev@ozlabs•org, paulus@samba•org
Subject: Re: question about softirqs
Date: Mon, 11 May 2009 12:25:54 -0600 [thread overview]
Message-ID: <4A086DB2.8040703@nortel.com> (raw)
In-Reply-To: <20090508.234815.127227651.davem@davemloft.net>
David Miller wrote:
> You know, for networking over loopback (one of the only real cases
> that even matters, if we get a hard interrupt then the return from
> that would process any softints), we probably make out just fine
> anyways. As long as we hit a local_bh_enable() (and in the return
> path from device transmit that's exceedingly likely as all of the
> networking locking is BH safe) we'll run the softints from that and
> thus long before we get to syscall return.
What about the issue I raised earlier? (I don't think you were copied
at that point.)
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.
(And maybe longer if NOHZ is enabled.)
Chris
next prev parent reply other threads:[~2009-05-11 18:26 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-08 22:51 question about softirqs Chris Friesen
2009-05-08 23:05 ` David Miller
2009-05-08 23:34 ` Paul Mackerras
2009-05-08 23:53 ` David Miller
2009-05-09 2:52 ` Benjamin Herrenschmidt
2009-05-09 3:31 ` Paul Mackerras
2009-05-09 6:48 ` David Miller
2009-05-11 18:25 ` Chris Friesen [this message]
2009-05-11 23:24 ` David Miller
2009-05-12 0:43 ` Chris Friesen
2009-05-12 8:12 ` Ingo Molnar
2009-05-12 9:12 ` Peter Zijlstra
2009-05-12 9:23 ` Ingo Molnar
2009-05-12 9:32 ` Peter Zijlstra
2009-05-12 12:20 ` Steven Rostedt
2009-05-13 4:45 ` David Miller
2009-05-13 4:44 ` David Miller
2009-05-13 5:15 ` Paul Mackerras
2009-05-13 5:28 ` David Miller
2009-05-13 5:55 ` Evgeniy Polyakov
2009-05-12 15:18 ` Chris Friesen
2009-05-13 8:34 ` Andi Kleen
2009-05-13 13:23 ` Chris Friesen
2009-05-13 14:15 ` Andi Kleen
2009-05-13 14:17 ` Thomas Gleixner
2009-05-13 14:24 ` Andi Kleen
2009-05-13 14:54 ` Eric Dumazet
2009-05-13 15:02 ` Andi Kleen
2009-05-13 15:05 ` Chris Friesen
2009-05-13 15:54 ` Thomas Gleixner
2009-05-13 16:10 ` Chris Friesen
2009-05-13 17:01 ` Andi Kleen
2009-05-13 19:04 ` Chris Friesen
2009-05-13 19:13 ` Andi Kleen
2009-05-13 19:44 ` Chris Friesen
2009-05-13 19:53 ` Andi Kleen
2009-05-13 20:55 ` Thomas Gleixner
2009-05-11 23:34 ` Paul Mackerras
2009-05-09 0:28 ` Chris Friesen
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