From patchwork Sun Dec 9 17:20:02 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 10720159 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CABA413BF for ; Sun, 9 Dec 2018 17:20:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A58242A1D4 for ; Sun, 9 Dec 2018 17:20:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 99F152A262; Sun, 9 Dec 2018 17:20:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id E7EA62A260 for ; Sun, 9 Dec 2018 17:20:27 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7EE656E220; Sun, 9 Dec 2018 17:20:11 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from mail-ed1-x541.google.com (mail-ed1-x541.google.com [IPv6:2a00:1450:4864:20::541]) by gabe.freedesktop.org (Postfix) with ESMTPS id 66D9C6E220 for ; Sun, 9 Dec 2018 17:20:10 +0000 (UTC) Received: by mail-ed1-x541.google.com with SMTP id x30so7591926edx.2 for ; Sun, 09 Dec 2018 09:20:10 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=NmKQduTXwMG7/D60udlj0ubqscsA31Rut12BAIAQ/lw=; b=B+T8jsllud7S2vE0fFA6u+pecNlcnDQSVg5bUc4xKcFLTd8gufxwVmtSpxnbQoeO70 DfTppWmwHOM6Aokdnhpe+u8vms9kecnOyAZQ0knP6SDgUp4BwpyJeHVJwopgLekhyoZy B2FSlLNNSd6Kns31K+czys6AIXHHCaAyV8HPYgn6jUpNUCq3Rj0Ort8hijMbM9UZ/Rym OlwojQPoNwYV7kFhPbJN/KbFbbSvPFCa8noek+jTOfykc85Zl2QchWMiiWGHQiEVSFLe wHc87qC32Xo87nvlsApQn59vk+bZ+TRGWLNCga8rNMLcl0NrOOPgqfoN/c2ZOVZn/aQ2 LrHg== X-Gm-Message-State: AA+aEWb3/JolxrMFgDrJSMHR9wflHXs85UdqAW+wihQZBn15Q2csH8ZK bhEqzh1C4A2/zBIDLIM6kIlakOVvZ1w= X-Google-Smtp-Source: AFSGD/UZWag2rMPfFnFWcIiBLB++Rjt+JOIuqK0dAR0iqczk8II8TVUXV3J4MIC+8iuiYEQhanYOGg== X-Received: by 2002:a17:906:49c2:: with SMTP id w2-v6mr7619104ejv.117.1544376008471; Sun, 09 Dec 2018 09:20:08 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:569e:0:3106:d637:d723:e855]) by smtp.gmail.com with ESMTPSA id y16sm2682741edb.41.2018.12.09.09.20.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 09 Dec 2018 09:20:07 -0800 (PST) From: Daniel Vetter To: Intel Graphics Development Date: Sun, 9 Dec 2018 18:20:02 +0100 Message-Id: <20181209172002.27674-1-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.20.0.rc1 In-Reply-To: <20181207160126.22898-1-daniel.vetter@ffwll.ch> References: <20181207160126.22898-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH] drivers/base: use a worker for sysfs unbind X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Vetter , Daniel Vetter Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" X-Virus-Scanned: ClamAV using ClamSMTP Drivers might want to remove some sysfs files, which needs the same locks and ends up angering lockdep. Relevant snippet of the stack trace: kernfs_remove_by_name_ns+0x3b/0x80 bus_remove_driver+0x92/0xa0 acpi_video_unregister+0x24/0x40 i915_driver_unload+0x42/0x130 [i915] i915_pci_remove+0x19/0x30 [i915] pci_device_remove+0x36/0xb0 device_release_driver_internal+0x185/0x250 unbind_store+0xaf/0x180 kernfs_fop_write+0x104/0x190 I've stumbled over this because some new patches by Ram connect the snd-hda-intel unload (where we do use sysfs unbind) with the locking chains in the i915 unload code (but without creating a new loop), which upset our CI. But the bug is already there and can be easily reproduced by unbind i915 directly. No idea whether this is the correct place to fix this, should at least get CI happy again. Note that the bus locking is already done by device_release_driver -> device_release_driver_internal, so I dropped that part. Also note that we don't recheck that the device is still bound by the same driver, but neither does the current code do that without races. And I figured that's a obscure enough corner case to not bother. v2: Use a task work. An entirely async work leads to impressive fireworks in our CI, notably in the vtcon bind/unbind code. Task work will be as synchronous as the current code, and so keep all these preexisting races neatly tugged under the rug. Cc: Ramalingam C Signed-off-by: Daniel Vetter Reviewed-by: Chris Wilson --- drivers/base/bus.c | 35 +++++++++++++++++++++++++++++------ 1 file changed, 29 insertions(+), 6 deletions(-) diff --git a/drivers/base/bus.c b/drivers/base/bus.c index 8bfd27ec73d6..095c4a140d76 100644 --- a/drivers/base/bus.c +++ b/drivers/base/bus.c @@ -17,6 +17,7 @@ #include #include #include +#include #include "base.h" #include "power/power.h" @@ -174,22 +175,44 @@ static const struct kset_uevent_ops bus_uevent_ops = { static struct kset *bus_kset; +struct unbind_work { + struct callback_head twork; + struct device *dev; +}; + +void unbind_work_fn(struct callback_head *work) +{ + struct unbind_work *unbind_work = + container_of(work, struct unbind_work, twork); + + device_release_driver_internal(unbind_work->dev, NULL, + unbind_work->dev->parent); + put_device(unbind_work->dev); + kfree(unbind_work); +} + /* Manually detach a device from its associated driver. */ static ssize_t unbind_store(struct device_driver *drv, const char *buf, size_t count) { struct bus_type *bus = bus_get(drv->bus); + struct unbind_work *unbind_work; struct device *dev; int err = -ENODEV; dev = bus_find_device_by_name(bus, NULL, buf); if (dev && dev->driver == drv) { - if (dev->parent && dev->bus->need_parent_lock) - device_lock(dev->parent); - device_release_driver(dev); - if (dev->parent && dev->bus->need_parent_lock) - device_unlock(dev->parent); - err = count; + unbind_work = kmalloc(sizeof(*unbind_work), GFP_KERNEL); + if (unbind_work) { + unbind_work->dev = dev; + get_device(dev); + init_task_work(&unbind_work->twork, unbind_work_fn); + task_work_add(current, &unbind_work->twork, true); + + err = count; + } else { + err = -ENOMEM; + } } put_device(dev); bus_put(bus);