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().
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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 ]---
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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.kumar@linaro.org Acked-by: Charles Keepax ckeepax@opensource.wolfsonmicro.com --- V3->V4: - Send the right version of the patch, sent the older one by mistake earlier.
V2->V3: - Fixed a rebase conflict - sending only one patch with Charles Ack
V1->V2: - Use regulator_bulk_free() instead of open coding it. - Shorter backtrace - Reworded the last paragraph to make it more clear - Added a comment in code
drivers/mfd/wm8994-core.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/mfd/wm8994-core.c b/drivers/mfd/wm8994-core.c index 95e6bc55adbb..953d0790ffd5 100644 --- a/drivers/mfd/wm8994-core.c +++ b/drivers/mfd/wm8994-core.c @@ -393,8 +393,13 @@ static int wm8994_device_init(struct wm8994 *wm8994, int irq) BUG(); goto err; } - - ret = devm_regulator_bulk_get(wm8994->dev, wm8994->num_supplies, + + /* + * Can't use devres helper here as some of the supplies are provided by + * wm8994->dev's children (regulators) and those regulators are + * unregistered by the devres core before the supplies are freed. + */ + ret = regulator_bulk_get(wm8994->dev, wm8994->num_supplies, wm8994->supplies); if (ret != 0) { dev_err(wm8994->dev, "Failed to get supplies: %d\n", ret); @@ -404,7 +409,7 @@ static int wm8994_device_init(struct wm8994 *wm8994, int irq) ret = regulator_bulk_enable(wm8994->num_supplies, wm8994->supplies); if (ret != 0) { dev_err(wm8994->dev, "Failed to enable supplies: %d\n", ret); - goto err; + goto err_regulator_free; }
ret = wm8994_reg_read(wm8994, WM8994_SOFTWARE_RESET); @@ -595,6 +600,8 @@ static int wm8994_device_init(struct wm8994 *wm8994, int irq) err_enable: regulator_bulk_disable(wm8994->num_supplies, wm8994->supplies); +err_regulator_free: + regulator_bulk_free(wm8994->num_supplies, wm8994->supplies); err: mfd_remove_devices(wm8994->dev); return ret; @@ -605,6 +612,7 @@ static void wm8994_device_exit(struct wm8994 *wm8994) pm_runtime_disable(wm8994->dev); wm8994_irq_exit(wm8994); regulator_bulk_disable(wm8994->num_supplies, wm8994->supplies); + regulator_bulk_free(wm8994->num_supplies, wm8994->supplies); mfd_remove_devices(wm8994->dev); }