GPIO Name Support

[  113.349395]
[  113.351013] ======================================================
[  113.357513] [ INFO: possible circular locking dependency detected ]
[  113.364135] 4.2.0-rc4-custom-00009-g0f75576-dirty #35 Not tainted
[  113.370574] -------------------------------------------------------
[  113.377166] sh/1619 is trying to acquire lock:
[  113.381866]  (s_active#138){++++.+}, at: [<c02032ac>] kernfs_remove_by_name_ns+0x4c/0x98
[  113.390502]
[  113.390502] but task is already holding lock:
[  113.396636]  (sysfs_lock){+.+.+.}, at: [<c03cf360>] gpiod_unexport+0x28/0xc8
[  113.404144]
[  113.404144] which lock already depends on the new lock.
[  113.404144]
[  113.412780]
[  113.412780] the existing dependency chain (in reverse order) is:
[  113.420654]
-> #1 (sysfs_lock){+.+.+.}:
[  113.424926]        [<c06f09d4>] mutex_lock_nested+0x48/0x3e0
[  113.430908]        [<c03ce6b4>] gpio_name_show+0x28/0x68
[  113.436553]        [<c045e744>] dev_attr_show+0x2c/0x58
[  113.442077]        [<c0204c38>] sysfs_kf_seq_show+0x98/0x10c
[  113.448059]        [<c02034c8>] kernfs_seq_show+0x34/0x38
[  113.453765]        [<c01b1454>] seq_read+0x1d0/0x4ac
[  113.459045]        [<c0203e54>] kernfs_fop_read+0x12c/0x188
[  113.464935]        [<c018a14c>] __vfs_read+0x38/0xe4
[  113.470184]        [<c018aa10>] vfs_read+0x88/0x110
[  113.475341]        [<c018b328>] SyS_read+0x54/0xb0
[  113.480407]        [<c000fd80>] ret_fast_syscall+0x0/0x54
[  113.486114]
-> #0 (s_active#138){++++.+}:
[  113.490600]        [<c009c2dc>] lock_acquire+0xac/0x124
[  113.496124]        [<c02022bc>] __kernfs_remove+0x234/0x300
[  113.502014]        [<c02032ac>] kernfs_remove_by_name_ns+0x4c/0x98
[  113.508544]        [<c0205af0>] remove_files.isra.1+0x40/0x88
[  113.514617]        [<c0205e68>] sysfs_remove_group+0x54/0xa8
[  113.520629]        [<c0205ef0>] sysfs_remove_groups+0x34/0x44
[  113.526702]        [<c045def8>] device_remove_attrs+0x4c/0x7c
[  113.532775]        [<c045e980>] device_del+0x114/0x224
[  113.538208]        [<c045eaac>] device_unregister+0x1c/0x30
[  113.544097]        [<c03cf3a0>] gpiod_unexport+0x68/0xc8
[  113.549713]        [<c03cb6f0>] __gpiod_free+0x1c/0xec
[  113.555145]        [<c03cd69c>] gpiod_free+0x20/0x50
[  113.560394]        [<c03cef68>] unexport_store+0xb0/0xe0
[  113.566009]        [<c0463560>] class_attr_store+0x28/0x34
[  113.571838]        [<c0204b04>] sysfs_kf_write+0x5c/0x60
[  113.577453]        [<c0203c44>] kernfs_fop_write+0xcc/0x1b0
[  113.583343]        [<c018a230>] __vfs_write+0x38/0xec
[  113.588684]        [<c018ab38>] vfs_write+0xa0/0x174
[  113.593933]        [<c018b3d8>] SyS_write+0x54/0xb0
[  113.599090]        [<c000fd80>] ret_fast_syscall+0x0/0x54
[  113.604797]
[  113.604797] other info that might help us debug this:
[  113.604797]
[  113.613250]  Possible unsafe locking scenario:
[  113.613250]
[  113.619506]        CPU0                    CPU1
[  113.624298]        ----                    ----
[  113.629058]   lock(sysfs_lock);
[  113.632385]                                lock(s_active#138);
[  113.638580]                                lock(sysfs_lock);
[  113.644561]   lock(s_active#138);
[  113.648101]
[  113.648101]  *** DEADLOCK ***
[  113.648101]
[  113.654357] 4 locks held by sh/1619:
[  113.658111]  #0:  (sb_writers#4){.+.+.+}, at: [<c018abe4>] vfs_write+0x14c/0x174
[  113.665985]  #1:  (&of->mutex){+.+.+.}, at: [<c0203bd4>] kernfs_fop_write+0x5c/0x1b0
[  113.674224]  #2:  (s_active#143){.+.+.+}, at: [<c0203bdc>] kernfs_fop_write+0x64/0x1b0
[  113.682647]  #3:  (sysfs_lock){+.+.+.}, at: [<c03cf360>] gpiod_unexport+0x28/0xc8
[  113.690612]
[  113.690612] stack backtrace:
[  113.695220] CPU: 0 PID: 1619 Comm: sh Not tainted 4.2.0-rc4-custom-00009-g0f75576-dirty #35
[  113.704010] Hardware name: Generic OMAP36xx (Flattened Device Tree)
[  113.710662] [<c00188a4>] (unwind_backtrace) from [<c00141f8>] (show_stack+0x20/0x24)
[  113.718841] [<c00141f8>] (show_stack) from [<c06ec9b4>] (dump_stack+0x8c/0xa4)
[  113.726470] [<c06ec9b4>] (dump_stack) from [<c0097ccc>] (print_circular_bug+0x1d4/0x320)
[  113.735015] [<c0097ccc>] (print_circular_bug) from [<c009b72c>] (__lock_acquire+0x1b88/0x1ed0)
[  113.744140] [<c009b72c>] (__lock_acquire) from [<c009c2dc>] (lock_acquire+0xac/0x124)
[  113.752410] [<c009c2dc>] (lock_acquire) from [<c02022bc>] (__kernfs_remove+0x234/0x300)
[  113.760833] [<c02022bc>] (__kernfs_remove) from [<c02032ac>] (kernfs_remove_by_name_ns+0x4c/0x98)
[  113.770233] [<c02032ac>] (kernfs_remove_by_name_ns) from [<c0205af0>] (remove_files.isra.1+0x40/0x88)
[  113.779937] [<c0205af0>] (remove_files.isra.1) from [<c0205e68>] (sysfs_remove_group+0x54/0xa8)
[  113.789123] [<c0205e68>] (sysfs_remove_group) from [<c0205ef0>] (sysfs_remove_groups+0x34/0x44)
[  113.798339] [<c0205ef0>] (sysfs_remove_groups) from [<c045def8>] (device_remove_attrs+0x4c/0x7c)
[  113.807617] [<c045def8>] (device_remove_attrs) from [<c045e980>] (device_del+0x114/0x224)
[  113.816253] [<c045e980>] (device_del) from [<c045eaac>] (device_unregister+0x1c/0x30)
[  113.824523] [<c045eaac>] (device_unregister) from [<c03cf3a0>] (gpiod_unexport+0x68/0xc8)
[  113.833160] [<c03cf3a0>] (gpiod_unexport) from [<c03cb6f0>] (__gpiod_free+0x1c/0xec)
[  113.841339] [<c03cb6f0>] (__gpiod_free) from [<c03cd69c>] (gpiod_free+0x20/0x50)
[  113.849151] [<c03cd69c>] (gpiod_free) from [<c03cef68>] (unexport_store+0xb0/0xe0)
[  113.857147] [<c03cef68>] (unexport_store) from [<c0463560>] (class_attr_store+0x28/0x34)
[  113.865692] [<c0463560>] (class_attr_store) from [<c0204b04>] (sysfs_kf_write+0x5c/0x60)
[  113.874237] [<c0204b04>] (sysfs_kf_write) from [<c0203c44>] (kernfs_fop_write+0xcc/0x1b0)
[  113.882873] [<c0203c44>] (kernfs_fop_write) from [<c018a230>] (__vfs_write+0x38/0xec)
[  113.891143] [<c018a230>] (__vfs_write) from [<c018ab38>] (vfs_write+0xa0/0x174)
[  113.898864] [<c018ab38>] (vfs_write) from [<c018b3d8>] (SyS_write+0x54/0xb0)
[  113.906311] [<c018b3d8>] (SyS_write) from [<c000fd80>] (ret_fast_syscall+0x0/0x54)