From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5AFFAC4332F for ; Fri, 18 Nov 2022 09:14:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241805AbiKRJN6 (ORCPT ); Fri, 18 Nov 2022 04:13:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235275AbiKRJN4 (ORCPT ); Fri, 18 Nov 2022 04:13:56 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CB7385FF0; Fri, 18 Nov 2022 01:13:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=mwt73Igv1Cbi6CXwxAPKd0Pr+R9hvpBvRt03pYQ3bys=; b=ab3Y1GXh5hZN4kYCUal3zeuK3Q 7SRG1cvzhO7eKodvFDYyuRae96G8g5PWd/XWhtSWcEI5MUsYEab5Ovzc8ze8gBOk9y9y/n4/VG6QA kxoDu7O/fG1a2giqiMnnG8GWp7V1BxUra+Jgp+oiupx2occO6L51vWUZQgeu4+7U3imdC7NUUUJ2N J5VaNoVksNMD06l+gxDbRhfwA3keSj0mXPL1+LX088MVxqFi6HWwWMGwF0jamw9uSp14pYO1PV0sb dSKJCydBYVIQlrwj2um9MWjTnI+ZTo1PEgHrvF9BZHJpiPATdBDwJ3bT9CqtMVsKHp/fep69BWHYQ 1FAlMbCA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1ovxQb-00287L-Gd; Fri, 18 Nov 2022 09:12:54 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 78E20300487; Fri, 18 Nov 2022 10:12:43 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 5E8232C316131; Fri, 18 Nov 2022 10:12:43 +0100 (CET) Date: Fri, 18 Nov 2022 10:12:43 +0100 From: Peter Zijlstra To: Valentin Schneider Cc: linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, x86@kernel.org, "Paul E. McKenney" , Steven Rostedt , Thomas Gleixner , Sebastian Andrzej Siewior , Juri Lelli , Daniel Bristot de Oliveira , Marcelo Tosatti , Frederic Weisbecker , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Marc Zyngier , Mark Rutland , Russell King , Nicholas Piggin , Guo Ren , "David S. Miller" Subject: Re: [RFC PATCH v2 8/8] sched, smp: Trace smp callback causing an IPI Message-ID: References: <20221102182949.3119584-1-vschneid@redhat.com> <20221102183336.3120536-7-vschneid@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Thu, Nov 17, 2022 at 02:45:29PM +0000, Valentin Schneider wrote: > > + if (trace_ipi_send_cpumask_enabled()) { > > + call_single_data_t *csd; > > + smp_call_func_t func; > > + > > + csd = container_of(node, call_single_data_t, node.llist); > > + > > + func = sched_ttwu_pending; > > + if (CSD_TYPE(csd) != CSD_TYPE_TTWU) > > + func = csd->func; > > + > > + if (raw_smp_call_single_queue(cpu, node)) > > + trace_ipi_send_cpumask(cpumask_of(cpu), _RET_IP_, func); > > So I went with the tracepoint being placed *before* the actual IPI gets > sent to have a somewhat sane ordering between trace_ipi_send_cpumask() and > e.g. trace_call_function_single_entry(). > > Packaging the call_single_queue logic makes the code less horrible, but it > does mix up the event ordering... Keeps em sharp ;-) > > + return; > > + } > > + > > + raw_smp_call_single_queue(cpu, node); > > } > > > > /* > > @@ -983,10 +1017,13 @@ static void smp_call_function_many_cond( > > * number of CPUs might be zero due to concurrent changes to the > > * provided mask. > > */ > > - if (nr_cpus == 1) > > + if (nr_cpus == 1) { > > + trace_ipi_send_cpumask(cpumask_of(last_cpu), _RET_IP_, func); > > send_call_function_single_ipi(last_cpu); > > This'll yield an IPI event even if no IPI is sent due to the idle task > polling, no? Oh, right..