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 smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 499BBE77197 for ; Thu, 9 Jan 2025 17:45:21 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 1047182FBE; Thu, 9 Jan 2025 17:45:21 +0000 (UTC) X-Virus-Scanned: amavis at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavis, port 10024) with ESMTP id cO0bvS8kxr85; Thu, 9 Jan 2025 17:45:19 +0000 (UTC) X-Comment: SPF check N/A for local connections - client-ip=140.211.166.142; helo=lists1.osuosl.org; envelope-from=intel-wired-lan-bounces@osuosl.org; receiver= DKIM-Filter: OpenDKIM Filter v2.11.0 smtp1.osuosl.org C8CD582FA5 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osuosl.org; s=default; t=1736444719; bh=ITDbkQWE/hIVhZw2Nq8W6mx+3e492XIMVSSt0BOfbNU=; h=Date:From:To:Cc:References:In-Reply-To:Subject:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=sBT4CtPBK6YmFD3bpIn6mpousl3kti+CR0JkkhbNLeJfzJaZ5Wfd8WjUgQDdAuSga 9hwSpJs/Rcp+pJsDDiUL+GAkHBCQCZ6KcoO0p/O+2mdh6+2mI5kX7jVrMUd+8dSOLd Kp7I/1sx6eNZNjdvk4e37y6esNTe1z+YZQ0oS6zWabK5WOtiZnobn5ECOVyYdwGMcl 0lFo7eN5XLv9eOHwUhoqKV5oIT22vfpwBaxvWcpq8OaKz0sdMvCH+envca3kgFb5bK Z6P4/En0tfav3al2jPEvwJdZlV5Nr9KPKdORjmPHAWq07kCQmoB8psNA0LTcs7SPrA AUolqsB3R23PA== Received: from lists1.osuosl.org (lists1.osuosl.org [140.211.166.142]) by smtp1.osuosl.org (Postfix) with ESMTP id C8CD582FA5; Thu, 9 Jan 2025 17:45:19 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [IPv6:2605:bc80:3010::137]) by lists1.osuosl.org (Postfix) with ESMTP id 9E627942 for ; Thu, 9 Jan 2025 17:45:18 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 7E8514071D for ; Thu, 9 Jan 2025 17:45:18 +0000 (UTC) X-Virus-Scanned: amavis at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavis, port 10024) with ESMTP id 2uHBpmsQU17W for ; Thu, 9 Jan 2025 17:45:17 +0000 (UTC) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=2a0a:51c0:0:12e:550::1; helo=galois.linutronix.de; envelope-from=bigeasy@linutronix.de; receiver= DMARC-Filter: OpenDMARC Filter v1.4.2 smtp4.osuosl.org 6E66440718 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp4.osuosl.org 6E66440718 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by smtp4.osuosl.org (Postfix) with ESMTPS id 6E66440718 for ; Thu, 9 Jan 2025 17:45:17 +0000 (UTC) Date: Thu, 9 Jan 2025 18:45:12 +0100 From: Sebastian Andrzej Siewior To: Wander Lairson Costa Cc: Tony Nguyen , Przemek Kitszel , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Clark Williams , Steven Rostedt , Jeff Garzik , Auke Kok , "moderated list:INTEL ETHERNET DRIVERS" , "open list:NETWORKING DRIVERS" , open list , "open list:Real-time Linux (PREEMPT_RT):Keyword:PREEMPT_RT" Message-ID: <20250109174512.At7ZERjU@linutronix.de> References: <20241204114229.21452-1-wander@redhat.com> <20250107135106.WWrtBMXY@linutronix.de> <20250108102532.VWnKWvoo@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1736444714; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ITDbkQWE/hIVhZw2Nq8W6mx+3e492XIMVSSt0BOfbNU=; b=wTdOlWbQ91hilUGbM16VU/8j5nkkTWdg5HJnuFCuQd/GAZAaWr+puLg3RtzuPF9cZXz+YX WkcVIjtFD+P4FdlEYxMNVG6JQ3Tc/wA3nrh/vIUDJ6OklF2IMhByt4DRQibSdUk6ByTpDq z2hchp5Z3Vmsqf1hWtdcHsdwjL2VuYCViTG9bnReSk4/27uV0sWHrbIPMalIESqSmtyaQl apXWsvjNjQpe28NHY1NLXpbmzSESTdHVy1Bqwrj24zApmWSu54gICF47aXNErnKTlBoH2u jgrtrBWmuKwchINQNd0UOt2ozMkbJySorYKiV0dsniatCnvepE7coKSI3kjhaA== X-Mailman-Original-DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1736444714; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ITDbkQWE/hIVhZw2Nq8W6mx+3e492XIMVSSt0BOfbNU=; b=yT3+jiuCw+WM1LYsNIad/JIuKA14d7jM3TedjhRkLbOSCxz3HARUlqSyEd5ZS4roS/3Eca N2TekSHFJbNwaeCg== X-Mailman-Original-Authentication-Results: smtp4.osuosl.org; dmarc=pass (p=none dis=none) header.from=linutronix.de X-Mailman-Original-Authentication-Results: smtp4.osuosl.org; dkim=pass (2048-bit key, unprotected) header.d=linutronix.de header.i=@linutronix.de header.a=rsa-sha256 header.s=2020 header.b=wTdOlWbQ; dkim=pass header.d=linutronix.de header.i=@linutronix.de header.a=ed25519-sha256 header.s=2020e header.b=yT3+jiuC Subject: Re: [Intel-wired-lan] [PATCH iwl-net 0/4] igb: fix igb_msix_other() handling for PREEMPT_RT X-BeenThere: intel-wired-lan@osuosl.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Intel Wired Ethernet Linux Kernel Driver Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-wired-lan-bounces@osuosl.org Sender: "Intel-wired-lan" On 2025-01-09 13:46:47 [-0300], Wander Lairson Costa wrote: > > If the issue is indeed the use of threaded interrupts then the fix > > should not be limited to be PREEMPT_RT only. > > > Although I was not aware of this scenario, the patch should work for it a= s well, > as I am forcing it to run in interrupt context. I will test it to confirm. If I remember correctly there were "ifdef preempt_rt" things in it. > > > > - What causes the failure? I see you reworked into two parts to beh= ave > > > > similar to what happens without threaded interrupts. There is sti= ll no > > > > explanation for it. Is there a timing limit or was there another > > > > register operation which removed the mailbox message? > > > > > > > > > > I explained the root cause of the issue in the last commit. Maybe I s= hould > > > have added the explanation to the cover letter as well. Anyway, here= is a > > > partial verbatim copy of it: > > > > > > "During testing of SR-IOV, Red Hat QE encountered an issue where the > > > ip link up command intermittently fails for the igbvf interfaces when > > > using the PREEMPT_RT variant. Investigation revealed that > > > e1000_write_posted_mbx returns an error due to the lack of an ACK > > > from e1000_poll_for_ack. > > > > That ACK would have come if it would poll longer? > > > No, the service wouldn't be serviced while polling. Hmm.=20 > > > The underlying issue arises from the fact that IRQs are threaded by > > > default under PREEMPT_RT. While the exact hardware details are not > > > available, it appears that the IRQ handled by igb_msix_other must > > > be processed before e1000_poll_for_ack times out. However, > > > e1000_write_posted_mbx is called with preemption disabled, leading > > > to a scenario where the IRQ is serviced only after the failure of > > > e1000_write_posted_mbx." > > > > Where is this disabled preemption coming from? This should be one of the > > ops.write_posted() calls, right? I've been looking around and don't see > > anything obvious. >=20 > I don't remember if I found the answer by looking at the code or by > looking at the ftrace flags. > I am currently on sick leave with covid. I can check it when I come back. Don't worry, get better first. I'm kind of off myself. I'm not sure if I have the hardware needed to setup so I can look at it=E2=80=A6 Sebastian