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) > [<c010e24c>] (unwind_backtrace) from [<c010af38>] (show_stack+0x10/0x14) > [<c010af38>] (show_stack) from [<c032a1c4>] (dump_stack+0x88/0x9c) > [<c032a1c4>] (dump_stack) from [<c011a98c>] (__warn+0xe8/0x100) > [<c011a98c>] (__warn) from [<c011aa54>] (warn_slowpath_null+0x20/0x28) > [<c011aa54>] (warn_slowpath_null) from [<c0384a0c>] > (regulator_unregister+0xc8/0xd0) > [<c0384a0c>] (regulator_unregister) from [<c0406434>] > (release_nodes+0x16c/0x1dc) > [<c0406434>] (release_nodes) from [<c04039c4>] > (__device_release_driver+0x8c/0x110) > [<c04039c4>] (__device_release_driver) from [<c0403a64>] > (device_release_driver+0x1c/0x28) > [<c0403a64>] (device_release_driver) from [<c0402b24>] > (bus_remove_device+0xd8/0x104) > [<c0402b24>] (bus_remove_device) from [<c03ffcd8>] (device_del+0x10c/0x218) > [<c03ffcd8>] (device_del) from [<c0404e4c>] (platform_device_del+0x1c/0x88) > [<c0404e4c>] (platform_device_del) from [<c0404ec4>] > (platform_device_unregister+0xc/0x20) > [<c0404ec4>] (platform_device_unregister) from [<c0428bc0>] > (mfd_remove_devices_fn+0x5c/0x64) > [<c0428bc0>] (mfd_remove_devices_fn) from [<c03ff9d8>] > (device_for_each_child_reverse+0x4c/0x78) > [<c03ff9d8>] (device_for_each_child_reverse) from [<c04288c4>] > (mfd_remove_devices+0x20/0x30) > [<c04288c4>] (mfd_remove_devices) from [<c042758c>] > (wm8994_device_init+0x2ac/0x7f0) > [<c042758c>] (wm8994_device_init) from [<c04f14a8>] > (i2c_device_probe+0x178/0x1fc) > [<c04f14a8>] (i2c_device_probe) from [<c04036fc>] > (driver_probe_device+0x214/0x2c0) > [<c04036fc>] (driver_probe_device) from [<c0403854>] > (__driver_attach+0xac/0xb0) > [<c0403854>] (__driver_attach) from [<c0401a74>] (bus_for_each_dev+0x68/0x9c) > [<c0401a74>] (bus_for_each_dev) from [<c0402cf0>] > (bus_add_driver+0x1a0/0x218) > [<c0402cf0>] (bus_add_driver) from [<c040406c>] (driver_register+0x78/0xf8) > [<c040406c>] (driver_register) from [<c04f20a0>] > (i2c_register_driver+0x34/0x84) > [<c04f20a0>] (i2c_register_driver) from [<c01017d0>] > (do_one_initcall+0x40/0x170) > [<c01017d0>] (do_one_initcall) from [<c0a00dbc>] > (kernel_init_freeable+0x15c/0x1fc) > [<c0a00dbc>] (kernel_init_freeable) from [<c06e07b0>] (kernel_init+0x8/0x114) > [<c06e07b0>] (kernel_init) from [<c0107978>] (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..] > > [<c06e489c>] (down_write) from [<c02e9954>] > (debugfs_remove_recursive+0x30/0x150) > [<c02e9954>] (debugfs_remove_recursive) from [<c0382b78>] > (_regulator_put+0x24/0xac) > [<c0382b78>] (_regulator_put) from [<c0382c1c>] (regulator_put+0x1c/0x2c) > [<c0382c1c>] (regulator_put) from [<c0406434>] (release_nodes+0x16c/0x1dc) > [<c0406434>] (release_nodes) from [<c04035d4>] > (driver_probe_device+0xec/0x2c0) > [<c04035d4>] (driver_probe_device) from [<c0403854>] > (__driver_attach+0xac/0xb0) > [<c0403854>] (__driver_attach) from [<c0401a74>] (bus_for_each_dev+0x68/0x9c) > [<c0401a74>] (bus_for_each_dev) from [<c0402cf0>] > (bus_add_driver+0x1a0/0x218) > [<c0402cf0>] (bus_add_driver) from [<c040406c>] (driver_register+0x78/0xf8) > [<c040406c>] (driver_register) from [<c04f20a0>] > (i2c_register_driver+0x34/0x84) > [<c04f20a0>] (i2c_register_driver) from [<c01017d0>] > (do_one_initcall+0x40/0x170) > [<c01017d0>] (do_one_initcall) from [<c0a00dbc>] > (kernel_init_freeable+0x15c/0x1fc) > [<c0a00dbc>] (kernel_init_freeable) from [<c06e07b0>] (kernel_init+0x8/0x114) > [<c06e07b0>] (kernel_init) from [<c0107978>] (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 <viresh.ku...@linaro.org> > > ---
Acked-by: Charles Keepax <ckee...@opensource.wolfsonmicro.com> Thanks, Charles
