Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966729AbbDXJAm (ORCPT ); Fri, 24 Apr 2015 05:00:42 -0400 Received: from goliath.siemens.de ([192.35.17.28]:48433 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934430AbbDXJAi (ORCPT ); Fri, 24 Apr 2015 05:00:38 -0400 Message-ID: <553A062D.6090608@siemens.com> Date: Fri, 24 Apr 2015 11:00:29 +0200 From: Jan Kiszka User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 To: Mike Galbraith , Steven Rostedt CC: Sebastian Andrzej Siewior , RT , Linux Kernel Mailing List Subject: Re: [PATCH RT 3.18] irq_work: Provide a soft-irq based queue References: <552FC1FE.4020406@siemens.com> <552FC6B1.1040000@linutronix.de> <552FC72A.8060709@siemens.com> <20150416111041.66043164@gandalf.local.home> <552FD55F.8000105@siemens.com> <552FE320.6050601@siemens.com> <1429517036.3226.9.camel@gmail.com> <1429769505.3419.9.camel@gmail.com> <55389632.50308@siemens.com> <1429772482.3419.40.camel@gmail.com> <55389B67.3000703@siemens.com> <1429773566.3419.42.camel@gmail.com> <20150423170026.0de65c90@gandalf.local.home> <1429858489.3461.28.camel@gmail.com> In-Reply-To: <1429858489.3461.28.camel@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3204 Lines: 71 On 2015-04-24 08:54, Mike Galbraith wrote: > On Thu, 2015-04-23 at 17:00 -0400, Steven Rostedt wrote: >> On Thu, 23 Apr 2015 09:19:26 +0200 >> Mike Galbraith wrote: >> >>>> CC kernel/irq_work.o >>>> In file included from ../include/asm-generic/percpu.h:6:0, >>>> from ../arch/x86/include/asm/percpu.h:522, >>>> from ../arch/x86/include/asm/current.h:5, >>>> from ../arch/x86/include/asm/processor.h:15, >>>> from ../arch/x86/include/asm/irq_work.h:4, >>>> from ../include/linux/irq_work.h:47, >>>> from ../kernel/irq_work.c:11: >>>> ../kernel/irq_work.c: In function ‘irq_work_queue_on’: >>>> ../kernel/irq_work.c:85:17: error: ‘hirq_work_list’ undeclared >>>> (first use in this function) >>>> &per_cpu(hirq_work_list, cpu)); >>> >>> Aw poo, so that's just what I _thought_ it was for. >> >> It helps optimization but does nothing for undefined symbols. >> >> That said, why don't we clean up that irq_work code and at least >> declare both lists, and get rid of all the #ifdefs. I wonder if gcc is >> smart enough to not allocate a static variable if it happens to be >> optimized out? > > Nope, it didn't notice a thing. > > This is a stab at that cleanup. Usable as is with Jan's ok, or as > fodder for your bitmaster-9000 patch shredder, or whatever. Box works > and it makes line count shrink... > > I downgraded evolution v3.16->v3.12 to restore its ability to read it's > own fscking "Preformatted" switch, so whitespace should be fine. > > Oh, btw, if anyone (else) makes a 4.1-rt, your rt push work will want > one of those nifty hirq tags lest box make boom due to trying to do that > not only way late, but with irqs enabled which pisses sched all off. > > Subject: [PATCH RT 3.18] irq_work: Provide a soft-irq based queue > Date: Thu, 16 Apr 2015 18:28:16 +0200 > From: Jan Kiszka > > Instead of turning all irq_work requests into lazy ones on -rt, just > move their execution from hard into soft-irq context. > > This resolves deadlocks of ftrace which will queue work from arbitrary > contexts, including those that have locks held that are needed for > raising a soft-irq. > > Mike: cleanup ifdef mess and kill hirq_work_list. We need two lists, > and already have them, merely need to select according to work type. > In -rt all work not tagged for hirq execution is queued to the lazy > list and runs via irq_work_tick(). Raising SOFTIRQ_TIMER is always > done via IPI for deadlock safety, if the work item is not a lazy work > or the tick is stopped, fire IPI immediately, otherwise let it wait. > IOW, lazy work is lazy in -rt only until someone queues immediate work. The approach looks good to me, but the commit log deserves a rework now. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/