From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757534AbcIPHip (ORCPT ); Fri, 16 Sep 2016 03:38:45 -0400 Received: from mx0b-001ae601.pphosted.com ([67.231.152.168]:48759 "EHLO mx0b-001ae601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752388AbcIPHig (ORCPT ); Fri, 16 Sep 2016 03:38:36 -0400 Authentication-Results: ppops.net; spf=none smtp.mailfrom=ckeepax@opensource.wolfsonmicro.com Date: Fri, 16 Sep 2016 08:38:38 +0100 From: Charles Keepax To: Viresh Kumar CC: Lee Jones , , "Mark Brown" , Krzysztof =?utf-8?Q?Koz=C5=82owski?= , , Subject: Re: [PATCH V2 3/3] mfd: wm8994-core: Don't use managed regulator bulk get API Message-ID: <20160916073838.GT21682@localhost.localdomain> References: <7d68a9e5dd338081342dd8b06310c2f3e61fccc0.1473996370.git.viresh.kumar@linaro.org> <00005c8c0b1294412c543604cb537622d6257416.1473996370.git.viresh.kumar@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <00005c8c0b1294412c543604cb537622d6257416.1473996370.git.viresh.kumar@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1609020000 definitions=main-1609160095 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 16, 2016 at 08:57:00AM +0530, Viresh Kumar wrote: > The kernel WARNs and then crashes today if wm8994_device_init() fails > after calling devm_regulator_bulk_get(). > > That happens because there are multiple devices involved here and the > order in which managed resources are freed isn't correct. > > The regulators are added as children of wm8994->dev. Whereas, > devm_regulator_bulk_get() receives wm8994->dev as the device, though it > gets the same regulators which were added as children of wm8994->dev > earlier. > > During failures, the children are removed first and the core eventually > calls regulator_unregister() for them. As regulator_put() was never done > for them (opposite of devm_regulator_bulk_get()), the kernel WARNs at > > WARN_ON(rdev->open_count); > > And eventually it crashes from debugfs_remove_recursive(). > > --------x------------------x---------------- > > wm8994 3-001a: Device is not a WM8994, ID is 0 > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 1 at /mnt/ssd/all/work/repos/devel/linux/drivers/regulator/core.c:4072 regulator_unregister+0xc8/0xd0 > Modules linked in: > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.0-rc6-00154-g54fe84cbd50b #41 > Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) > [] (unwind_backtrace) from [] (show_stack+0x10/0x14) > [] (show_stack) from [] (dump_stack+0x88/0x9c) > [] (dump_stack) from [] (__warn+0xe8/0x100) > [] (__warn) from [] (warn_slowpath_null+0x20/0x28) > [] (warn_slowpath_null) from [] (regulator_unregister+0xc8/0xd0) > [] (regulator_unregister) from [] (release_nodes+0x16c/0x1dc) > [] (release_nodes) from [] (__device_release_driver+0x8c/0x110) > [] (__device_release_driver) from [] (device_release_driver+0x1c/0x28) > [] (device_release_driver) from [] (bus_remove_device+0xd8/0x104) > [] (bus_remove_device) from [] (device_del+0x10c/0x218) > [] (device_del) from [] (platform_device_del+0x1c/0x88) > [] (platform_device_del) from [] (platform_device_unregister+0xc/0x20) > [] (platform_device_unregister) from [] (mfd_remove_devices_fn+0x5c/0x64) > [] (mfd_remove_devices_fn) from [] (device_for_each_child_reverse+0x4c/0x78) > [] (device_for_each_child_reverse) from [] (mfd_remove_devices+0x20/0x30) > [] (mfd_remove_devices) from [] (wm8994_device_init+0x2ac/0x7f0) > [] (wm8994_device_init) from [] (i2c_device_probe+0x178/0x1fc) > [] (i2c_device_probe) from [] (driver_probe_device+0x214/0x2c0) > [] (driver_probe_device) from [] (__driver_attach+0xac/0xb0) > [] (__driver_attach) from [] (bus_for_each_dev+0x68/0x9c) > [] (bus_for_each_dev) from [] (bus_add_driver+0x1a0/0x218) > [] (bus_add_driver) from [] (driver_register+0x78/0xf8) > [] (driver_register) from [] (i2c_register_driver+0x34/0x84) > [] (i2c_register_driver) from [] (do_one_initcall+0x40/0x170) > [] (do_one_initcall) from [] (kernel_init_freeable+0x15c/0x1fc) > [] (kernel_init_freeable) from [] (kernel_init+0x8/0x114) > [] (kernel_init) from [] (ret_from_fork+0x14/0x3c) > ---[ end trace 0919d3d0bc998260 ]--- > > [snip..] > > Unable to handle kernel NULL pointer dereference at virtual address 00000078 > pgd = c0004000 > [00000078] *pgd=00000000 > Internal error: Oops: 5 [#1] PREEMPT SMP ARM > Modules linked in: > CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 4.8.0-rc6-00154-g54fe84cbd50b #41 > Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) > task: ee874000 task.stack: ee878000 > PC is at down_write+0x14/0x54 > LR is at debugfs_remove_recursive+0x30/0x150 > > [snip..] > > [] (down_write) from [] (debugfs_remove_recursive+0x30/0x150) > [] (debugfs_remove_recursive) from [] (_regulator_put+0x24/0xac) > [] (_regulator_put) from [] (regulator_put+0x1c/0x2c) > [] (regulator_put) from [] (release_nodes+0x16c/0x1dc) > [] (release_nodes) from [] (driver_probe_device+0xec/0x2c0) > [] (driver_probe_device) from [] (__driver_attach+0xac/0xb0) > [] (__driver_attach) from [] (bus_for_each_dev+0x68/0x9c) > [] (bus_for_each_dev) from [] (bus_add_driver+0x1a0/0x218) > [] (bus_add_driver) from [] (driver_register+0x78/0xf8) > [] (driver_register) from [] (i2c_register_driver+0x34/0x84) > [] (i2c_register_driver) from [] (do_one_initcall+0x40/0x170) > [] (do_one_initcall) from [] (kernel_init_freeable+0x15c/0x1fc) > [] (kernel_init_freeable) from [] (kernel_init+0x8/0x114) > [] (kernel_init) from [] (ret_from_fork+0x14/0x3c) > Code: e1a04000 f590f000 e3a03001 e34f3fff (e1902f9f) > ---[ end trace 0919d3d0bc998262 ]--- > > --------x------------------x---------------- > > Fix the kernel warnings and crashes by using regulator_bulk_get() > instead of devm_regulator_bulk_get() and explicitly freeing the supplies > in exit paths. > > Tested on Exynos 5250, dual core ARM A15 machine. > > Signed-off-by: Viresh Kumar > > --- Acked-by: Charles Keepax Thanks, Charles