From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Chris Friesen" <cfriesen@nortel.com>
Subject: Re: question about softirqs
Date: Wed, 13 May 2009 10:10:37 -0600
Message-ID: <4A0AF0FD.9050501@nortel.com>
References: <18948.63755.279732.294842@cargo.ozlabs.ibm.com>
	<20090508.234815.127227651.davem@davemloft.net>
	<4A086DB2.8040703@nortel.com>
	<20090511.162436.193717082.davem@davemloft.net>
	<4A08C62F.1050105@nortel.com> <20090512081237.GA16403@elte.hu>
	<4A09933B.8010606@nortel.com> <874ovpmmdq.fsf@basil.nowhere.org>
	<4A0AC9EC.6070908@nortel.com>
	<20090513141532.GT19296@one.firstfloor.org>
	<alpine.LFD.2.00.0905131612180.3561@localhost.localdomain>
	<87my9hkrmw.fsf@basil.nowhere.org> <4A0AE19D.9040509@nortel.com>
	<alpine.LFD.2.00.0905131751150.3561@localhost.localdomain>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, netdev@vger.kernel.org,
	Steven Rostedt <rostedt@goodmis.org>, linuxppc-dev@ozlabs.org,
	Andi Kleen <andi@firstfloor.org>, paulus@samba.org,
	Ingo Molnar <mingo@elte.hu>, David Miller <davem@davemloft.net>
To: Thomas Gleixner <tglx@linutronix.de>
Return-path: <linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@ozlabs.org>
In-Reply-To: <alpine.LFD.2.00.0905131751150.3561@localhost.localdomain>
List-Unsubscribe: <https://ozlabs.org/mailman/options/linuxppc-dev>,
	<mailto:linuxppc-dev-request@ozlabs.org?subject=unsubscribe>
List-Archive: <http://ozlabs.org/pipermail/linuxppc-dev>
List-Post: <mailto:linuxppc-dev@ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@ozlabs.org?subject=help>
List-Subscribe: <https://ozlabs.org/mailman/listinfo/linuxppc-dev>,
	<mailto:linuxppc-dev-request@ozlabs.org?subject=subscribe>
Sender: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@ozlabs.org
Errors-To: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@ozlabs.org
List-Id: netdev.vger.kernel.org

Thomas Gleixner wrote:
> On Wed, 13 May 2009, Chris Friesen wrote:

>> As far as I can tell, in this scenario softirqs may not get processed on
>> return from a syscall (contradicting the documentation).  In the worst
>> case, they may not get processed until the next timer tick.
> 
> Right because your high prio tasks prevents that ksoftirqd runs,
> because it can not preempt the high priority task.

Exactly.

I'm suggesting that this point (the idea that softirqs may or may not
get processed on return from syscall depending on relative task
priority) should probably be documented somewhere, because the current
documentation (in the kernel and on the web) doesn't mention it at all.

Maybe I should just submit a patch to
Documentation/DocBook/kernel-hacking.tmpl.

Chris