From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750988AbWFTUeJ (ORCPT ); Tue, 20 Jun 2006 16:34:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750993AbWFTUeI (ORCPT ); Tue, 20 Jun 2006 16:34:08 -0400 Received: from www.osadl.org ([213.239.205.134]:50625 "EHLO mail.tglx.de") by vger.kernel.org with ESMTP id S1750988AbWFTUeG (ORCPT ); Tue, 20 Jun 2006 16:34:06 -0400 Subject: Re: Why can't I set the priority of softirq-hrt? (Re: 2.6.17-rt1) From: Thomas Gleixner Reply-To: tglx@linutronix.de To: Esben Nielsen Cc: Ingo Molnar , linux-kernel@vger.kernel.org In-Reply-To: References: <20060618070641.GA6759@elte.hu> <1150816429.6780.222.camel@localhost.localdomain> <1150821311.6780.240.camel@localhost.localdomain> Content-Type: text/plain Date: Tue, 20 Jun 2006 22:35:31 +0200 Message-Id: <1150835732.6780.293.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.6.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2006-06-20 at 22:16 +0100, Esben Nielsen wrote: > > We had this before and it is horrible. > > "Horrible" in what respect? Unbound latencies. > > A nice solution would be to enqueue the timer into the task struct of > > the thread which is target of the signal, wake that thread in a special > > state which only runs the callback and then does the signal delivery. > > What if the thread is running? Well, do it in the return from interrupt path. > Hmm, a practical thing to do would be to make a system where you can post > jobs in a thread. These jobs can then be done in thread context > around schedule or just before the task returns to user-space. Thats basically what I said. But you have to take care of asynchronous signal delivery. Therefor you need a special state. Also return to userspace is not enough. You have to do the check in the return from interrupt path, as you might delay async signals otherwise. tglx