From patchwork Thu Dec 13 04:01:05 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ramalingam C X-Patchwork-Id: 10727711 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 44EE314DE for ; Thu, 13 Dec 2018 04:06:47 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 34FF72B1B3 for ; Thu, 13 Dec 2018 04:06:47 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2905C2B89A; Thu, 13 Dec 2018 04:06:47 +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=unavailable 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 D44A02B1B3 for ; Thu, 13 Dec 2018 04:06:46 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 8792B6EC18; Thu, 13 Dec 2018 04:06:43 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by gabe.freedesktop.org (Postfix) with ESMTPS id 498016EC14; Thu, 13 Dec 2018 04:06:33 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Dec 2018 20:06:33 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,347,1539673200"; d="scan'208";a="109978346" Received: from mint-dev.iind.intel.com ([10.223.25.164]) by orsmga003.jf.intel.com with ESMTP; 12 Dec 2018 20:06:29 -0800 From: Ramalingam C To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, seanpaul@chromium.org, daniel.vetter@ffwll.ch, tomas.winkler@intel.com, uma.shankar@intel.com Subject: [PATCH v9 03/39] drivers/base: use a worker for sysfs unbind Date: Thu, 13 Dec 2018 09:31:05 +0530 Message-Id: <1544673701-6353-4-git-send-email-ramalingam.c@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1544673701-6353-1-git-send-email-ramalingam.c@intel.com> References: <1544673701-6353-1-git-send-email-ramalingam.c@intel.com> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Vetter MIME-Version: 1.0 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Daniel Vetter 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 --- 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);