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 X-Spam-Level: X-Spam-Status: No, score=-11.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 32522C63777 for ; Mon, 16 Nov 2020 15:53:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0155D207BC for ; Mon, 16 Nov 2020 15:53:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=st.com header.i=@st.com header.b="mTw81IH4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731333AbgKPPxA (ORCPT ); Mon, 16 Nov 2020 10:53:00 -0500 Received: from mx07-00178001.pphosted.com ([185.132.182.106]:55846 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730557AbgKPPxA (ORCPT ); Mon, 16 Nov 2020 10:53:00 -0500 Received: from pps.filterd (m0046037.ppops.net [127.0.0.1]) by mx07-00178001.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0AGFVYrS007504; Mon, 16 Nov 2020 16:51:54 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=st.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=STMicroelectronics; bh=ofXcc+v9fXz59wEvzmIye9sbUQclYuxy5ISsOnEz+Dc=; b=mTw81IH4Grra15CIuBOZIni8TuoSyM5WAggBXYdsBmhEam1YCxuHr2Vvl5eGvp6kKqHW sX0y68+J7JW41P82riCMqVQhhzTqaT6RWR5yX4NAz0yY8SGLVzxPtOvGACrkVJdYJfrG h1kuN8i5k1WrUgnYIiMS82OMcdeojnvmOFe1OL9IPj8MUh83+tkroJph7uJakeTpQAFJ WxRjywRU3A/agCBXQZTLMHRBTlm0DhJe14TTxJ4Rh3x3LDvQqES8X4OCbz9pfStNTG25 layfeiF6I6qIAXCdRdQBSVpLb8EEvrUGUQexp8FV+qdovanhoyWsoqSbXFUHXesqLtAy 2Q== Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx07-00178001.pphosted.com with ESMTP id 34t5w1kpsc-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 16 Nov 2020 16:51:54 +0100 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id 171B510002A; Mon, 16 Nov 2020 16:51:54 +0100 (CET) Received: from Webmail-eu.st.com (sfhdag3node1.st.com [10.75.127.7]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 0763720D62F; Mon, 16 Nov 2020 16:51:54 +0100 (CET) Received: from lmecxl0889.lme.st.com (10.75.127.51) by SFHDAG3NODE1.st.com (10.75.127.7) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Mon, 16 Nov 2020 16:51:53 +0100 Subject: Re: [PATCH v5 8/8] rpmsg: Turn name service into a stand alone driver To: Guennadi Liakhovetski CC: Mathieu Poirier , "ohad@wizery.com" , "bjorn.andersson@linaro.org" , "linux-remoteproc@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <20201106175332.GB3203364@xps15> <20201109102023.GA17692@ubuntu> <20201109175536.GD3395222@xps15> <20201111144942.GA6403@ubuntu> <20201112115115.GA11069@ubuntu> <945f377d-1975-552d-25b2-1dc25d3c3a46@st.com> <2d25d1aa-bd8a-f0db-7888-9f72edc9f687@st.com> <20201116151028.GA1519@ubuntu> From: Arnaud POULIQUEN Message-ID: Date: Mon, 16 Nov 2020 16:51:52 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201116151028.GA1519@ubuntu> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.75.127.51] X-ClientProxiedBy: SFHDAG2NODE1.st.com (10.75.127.4) To SFHDAG3NODE1.st.com (10.75.127.7) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-16_08:2020-11-13,2020-11-16 signatures=0 Precedence: bulk List-ID: X-Mailing-List: linux-remoteproc@vger.kernel.org Hi Guennadi, On 11/16/20 4:10 PM, Guennadi Liakhovetski wrote: > Hi Arnaud, > > On Mon, Nov 16, 2020 at 03:43:35PM +0100, Arnaud POULIQUEN wrote: >> Hi Guennadi, Mathieu, > > [snip] > >> I tried the find_module API, it's quite simple and seems to work well. just need >> to be protected by #ifdef MODULE >> >> I also added a select RMPS_NS in the RPMSG_VIRTIO for compatibility with the legacy. >> >> look to me that this patch is a simple fix that should work also for the vhost... >> that said, the question is can we use this API here? >> >> I attached the patch at the end of the mail. > > Thanks for the patch. Yes, this would guarantee, that the NS module is loaded. But > does it also guarantee, that the NS probing completes faster than an NS announcement > arrives? We have a race here: > > rpmsg_ns_register_device() -----------------\ > | | > virtio_device_ready() | > | | > remote sends NS announcement rpmsg_register_device() > | | > | rpmsg_ns_probe() > | | > | rpmsg_create_ept() > rpmsg_ns_cb() > > In practice we *should* be fine - maybe the whole probing (the right branch) happens > synchronously on the same core as where rpmsg_ns_register_device() was called, or > even if not, the probing runs locally and the NS announcement either talks to a > remote core or a VM. So, it *should* be safe, but unless we can make guarantee, that > the probing is synchronous, I wouldn't rely on this. So, without a completion this > still seems incomplete to me. Thanks for this description! I tested on a dual core, and I expected what you are describing above but in fact I observed following: rpmsg_ns_register_device() | rpmsg_register_device() | rpmsg_ns_probe() | rpmsg_create_ept() | virtio_device_ready() | remote sends NS announcement rpmsg_ns_cb() Here is the associated call stack generated in rpmsg_ns_probe using "warn_on" [ 11.498678] CPU: 1 PID: 348 Comm: systemd-udevd Not tainted 5.10.0-rc2 #54 [ 11.504106] Hardware name: STM32 (Device Tree Support) [ 11.509271] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [ 11.516992] [] (show_stack) from [] (dump_stack+0xb8/0xcc) [ 11.524204] [] (dump_stack) from [] (__warn+0xd8/0xf0) [ 11.531066] [] (__warn) from [] (warn_slowpath_fmt+0x64/0xc4) [ 11.538547] [] (warn_slowpath_fmt) from [] (rpmsg_ns_probe+0x5c/0xe0 [rpmsg_ns]) [ 11.547681] [] (rpmsg_ns_probe [rpmsg_ns]) from [] (rpmsg_dev_probe+0x14c/0x1b0 [rpmsg_core]) [ 11.557933] [] (rpmsg_dev_probe [rpmsg_core]) from [] (really_probe+0x208/0x4f0) [ 11.567050] [] (really_probe) from [] (driver_probe_device+0x78/0x16c) [ 11.575305] [] (driver_probe_device) from [] (bus_for_each_drv+0x84/0xd0) [ 11.583822] [] (bus_for_each_drv) from [] (__device_attach+0xf0/0x188) [ 11.592075] [] (__device_attach) from [] (bus_probe_device+0x84/0x8c) [ 11.600248] [] (bus_probe_device) from [] (device_add+0x3b0/0x7b0) [ 11.608165] [] (device_add) from [] (rpmsg_register_device+0x54/0x88 [rpmsg_core]) [ 11.617486] [] (rpmsg_register_device [rpmsg_core]) from [] (rpmsg_probe+0x2c4/0x3f4 [virtio_rpmsg_bus]) [ 11.628696] [] (rpmsg_probe [virtio_rpmsg_bus]) from [] (virtio_dev_probe+0x1f4/0x2c4) [ 11.638352] [] (virtio_dev_probe) from [] (really_probe+0x208/0x4f0) [ 11.646406] [] (really_probe) from [] (driver_probe_device+0x78/0x16c) [ 11.654658] [] (driver_probe_device) from [] (device_driver_attach+0x58/0x60) [ 11.663522] [] (device_driver_attach) from [] (__driver_attach+0xb4/0x154) [ 11.672134] [] (__driver_attach) from [] (bus_for_each_dev+0x78/0xc0) [ 11.680300] [] (bus_for_each_dev) from [] (bus_add_driver+0x170/0x20c) [ 11.688599] [] (bus_add_driver) from [] (driver_register+0x74/0x108) [ 11.696662] [] (driver_register) from [] (rpmsg_init+0x6c/0x1000 [virtio_rpmsg_bus]) [ 11.706136] [] (rpmsg_init [virtio_rpmsg_bus]) from [] (do_one_initcall+0x58/0x2bc) [ 11.713616] usb33: supplied by vdd_usb [ 11.715500] [] (do_one_initcall) from [] (do_init_module+0x60/0x248) [ 11.715525] [] (do_init_module) from [] (load_module+0x12e8/0x1638) [ 11.715546] [] (load_module) from [] (sys_finit_module+0xd4/0x130) [ 11.715575] [] (sys_finit_module) from [] (ret_fast_syscall+0x0/0x54) Having said that, does this guarantee the probe, a good question! Maybe you or Mathieu have the answer, not me... So if we can't conclude, adding completion would be OK for me. Thanks, Arnaud > > Thanks > Guennadi > >>>> Why can it not be called in rpmsg_ns_probe()? The only purpose of this completion >>>> is to make sure that rpmsg_create_ept() for the NS endpoint has completed before >>>> we begin communicating with the remote / host, e.g. by calling >>>> virtio_device_ready() in case of the VirtIO backend, right? >>> >>> How the module driver are probed during device registration is not cristal clear >>> for me here... >>> Your approach looks to me a good compromize, I definitively need to apply and >>> test you patch to well understood the associated scheduling... >> >> I looked in code, trying to understand behavior on device registration. >> >> my understanding is: if driver is already registered (basic built-in or module >> previously loaded) the driver is probed on device registration. No asynchronous >> probing through a work queue or other. >> >> So it seems, (but i'm not enough expert to be 100% sure) that ensuring that the >> rmpsg_ns module is loaded (and so driver registered) before the device register >> is enough, no completion mechanism is needed here. >> >> Regards, >> Arnaud >> >>> >>> Thanks, >>> Arnaud >>> >>>> >>>> Thanks >>>> Guennadi >>>> >>>>> Thanks, >>>>> Arnaud >>>>> >> >> [...] >> >> From 2629298ef1b7eea7a3a7df245abba03914c09e6b Mon Sep 17 00:00:00 2001 >> From: Arnaud Pouliquen >> Date: Mon, 16 Nov 2020 15:07:14 +0100 >> Subject: [PATCH] rpmsg: specify dependency between virtio rpmsg and virtio_ns >> >> The rpmsg_ns service has to be registered before the first >> message reception. When used as module, this imply and >> dependency of the rpmsg virtio on the rpmsg_ns module. >> this patch solve the dependency issue. >> >> Signed-off-by: Arnaud Pouliquen >> --- >> drivers/rpmsg/Kconfig | 1 + >> drivers/rpmsg/rpmsg_ns.c | 2 +- >> drivers/rpmsg/virtio_rpmsg_bus.c | 22 ++++++++++++++++++++++ >> 3 files changed, 24 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/rpmsg/Kconfig b/drivers/rpmsg/Kconfig >> index c3fc75e6514b..1394114782d2 100644 >> --- a/drivers/rpmsg/Kconfig >> +++ b/drivers/rpmsg/Kconfig >> @@ -71,5 +71,6 @@ config RPMSG_VIRTIO >> depends on HAS_DMA >> select RPMSG >> select VIRTIO >> + select RPMSG_NS >> >> endmenu >> diff --git a/drivers/rpmsg/rpmsg_ns.c b/drivers/rpmsg/rpmsg_ns.c >> index 5bda7cb44618..f19f3cbd2526 100644 >> --- a/drivers/rpmsg/rpmsg_ns.c >> +++ b/drivers/rpmsg/rpmsg_ns.c >> @@ -104,5 +104,5 @@ module_exit(rpmsg_ns_exit); >> >> MODULE_DESCRIPTION("Name service announcement rpmsg Driver"); >> MODULE_AUTHOR("Arnaud Pouliquen "); >> -MODULE_ALIAS("rpmsg_ns"); >> +MODULE_ALIAS("rpmsg:rpmsg_ns"); >> MODULE_LICENSE("GPL v2"); >> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c >> index 338f16c6563d..f032e6c3f9a9 100644 >> --- a/drivers/rpmsg/virtio_rpmsg_bus.c >> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c >> @@ -1001,6 +1001,28 @@ static int __init rpmsg_init(void) >> { >> int ret; >> >> +#ifdef MODULE >> + static const char name[] = "rpmsg_ns"; >> + struct module *ns; >> + >> + /* >> + * Make sur that the rpmsg ns module is loaded in case of module. >> + * This ensures that the rpmsg_ns driver is probed immediately when the >> + * associated device is registered during the rpmsg virtio probe. >> + */ >> + mutex_lock(&module_mutex); >> + ns = find_module(name); >> + mutex_unlock(&module_mutex); >> + >> + if (!ns) { >> + ret = request_module(name); >> + if (ret) { >> + pr_err("can not find %s module (err %d)\n", name, ret); >> + return ret; >> + } >> + } >> +#endif >> + >> ret = register_virtio_driver(&virtio_ipc_driver); >> if (ret) >> pr_err("failed to register virtio driver: %d\n", ret); >> -- >> 2.17.1