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i2c: suppress lockdep warning on delete_device
i2c: suppress lockdep warning on delete_device Since commit846f99749a
the following lockdep warning is thrown in case i2c device is removed (via delete_device sysfs attribute) which contains subdevices (e.g. i2c multiplexer): ============================================= [ INFO: possible recursive locking detected ] 3.8.7-0-sampleversion-fct #8 Tainted: G O --------------------------------------------- bash/3743 is trying to acquire lock: (s_active#110){++++.+}, at: [<ffffffff802b3048>] sysfs_hash_and_remove+0x58/0xc8 but task is already holding lock: (s_active#110){++++.+}, at: [<ffffffff802b3cb8>] sysfs_write_file+0xc8/0x208 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(s_active#110); lock(s_active#110); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by bash/3743: #0: (&buffer->mutex){+.+.+.}, at: [<ffffffff802b3c3c>] sysfs_write_file+0x4c/0x208 #1: (s_active#110){++++.+}, at: [<ffffffff802b3cb8>] sysfs_write_file+0xc8/0x208 #2: (&adap->userspace_clients_lock/1){+.+.+.}, at: [<ffffffff80454a18>] i2c_sysfs_delete_device+0x90/0x238 #3: (&__lockdep_no_validate__){......}, at: [<ffffffff803dcc24>] device_release_driver+0x24/0x48 stack backtrace: Call Trace: [<ffffffff80575cc8>] dump_stack+0x8/0x34 [<ffffffff801b50fc>] __lock_acquire+0x161c/0x2110 [<ffffffff801b5c3c>] lock_acquire+0x4c/0x70 [<ffffffff802b60cc>] sysfs_addrm_finish+0x19c/0x1e0 [<ffffffff802b3048>] sysfs_hash_and_remove+0x58/0xc8 [<ffffffff802b7d8c>] sysfs_remove_group+0x64/0x148 [<ffffffff803d990c>] device_remove_attrs+0x9c/0x1a8 [<ffffffff803d9b1c>] device_del+0x104/0x1d8 [<ffffffff803d9c18>] device_unregister+0x28/0x70 [<ffffffff8045505c>] i2c_del_adapter+0x1cc/0x328 [<ffffffff8045802c>] i2c_del_mux_adapter+0x14/0x38 [<ffffffffc025c108>] pca954x_remove+0x90/0xe0 [pca954x] [<ffffffff804542f8>] i2c_device_remove+0x80/0xe8 [<ffffffff803dca9c>] __device_release_driver+0x74/0xf8 [<ffffffff803dcc2c>] device_release_driver+0x2c/0x48 [<ffffffff803dbc14>] bus_remove_device+0x13c/0x1d8 [<ffffffff803d9b24>] device_del+0x10c/0x1d8 [<ffffffff803d9c18>] device_unregister+0x28/0x70 [<ffffffff80454b08>] i2c_sysfs_delete_device+0x180/0x238 [<ffffffff802b3cd4>] sysfs_write_file+0xe4/0x208 [<ffffffff8023ddc4>] vfs_write+0xbc/0x160 [<ffffffff8023df6c>] SyS_write+0x54/0xd8 [<ffffffff8013d424>] handle_sys64+0x44/0x64 The problem is already known for USB and PCI subsystems. The reason is that delete_device attribute is defined statically in i2c-core.c and used for all devices in i2c subsystem. Discussion of original USB problem: http://lkml.indiana.edu/hypermail/linux/kernel/1204.3/01160.html Commit356c05d58a
introduced new macro to suppress lockdep warnings for this special case and included workaround for USB code. LKML discussion of the workaround: http://lkml.indiana.edu/hypermail/linux/kernel/1205.1/03634.html As i2c case is in principle the same, the same workaround could be used here. Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nsn.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Tejun Heo <tj@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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@ -892,7 +892,8 @@ i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr,
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}
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static DEVICE_ATTR(new_device, S_IWUSR, NULL, i2c_sysfs_new_device);
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static DEVICE_ATTR(delete_device, S_IWUSR, NULL, i2c_sysfs_delete_device);
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static DEVICE_ATTR_IGNORE_LOCKDEP(delete_device, S_IWUSR, NULL,
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i2c_sysfs_delete_device);
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static struct attribute *i2c_adapter_attrs[] = {
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&dev_attr_name.attr,
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