From e9b526fe704812364bca07edd15eadeba163ebfb Mon Sep 17 00:00:00 2001 From: Alexander Sverdlin Date: Fri, 17 May 2013 14:56:35 +0200 Subject: [PATCH] i2c: suppress lockdep warning on delete_device i2c: suppress lockdep warning on delete_device Since commit 846f99749ab68bbc7f75c74fec305de675b1a1bf 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: [] sysfs_hash_and_remove+0x58/0xc8 but task is already holding lock: (s_active#110){++++.+}, at: [] 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: [] sysfs_write_file+0x4c/0x208 #1: (s_active#110){++++.+}, at: [] sysfs_write_file+0xc8/0x208 #2: (&adap->userspace_clients_lock/1){+.+.+.}, at: [] i2c_sysfs_delete_device+0x90/0x238 #3: (&__lockdep_no_validate__){......}, at: [] device_release_driver+0x24/0x48 stack backtrace: Call Trace: [] dump_stack+0x8/0x34 [] __lock_acquire+0x161c/0x2110 [] lock_acquire+0x4c/0x70 [] sysfs_addrm_finish+0x19c/0x1e0 [] sysfs_hash_and_remove+0x58/0xc8 [] sysfs_remove_group+0x64/0x148 [] device_remove_attrs+0x9c/0x1a8 [] device_del+0x104/0x1d8 [] device_unregister+0x28/0x70 [] i2c_del_adapter+0x1cc/0x328 [] i2c_del_mux_adapter+0x14/0x38 [] pca954x_remove+0x90/0xe0 [pca954x] [] i2c_device_remove+0x80/0xe8 [] __device_release_driver+0x74/0xf8 [] device_release_driver+0x2c/0x48 [] bus_remove_device+0x13c/0x1d8 [] device_del+0x10c/0x1d8 [] device_unregister+0x28/0x70 [] i2c_sysfs_delete_device+0x180/0x238 [] sysfs_write_file+0xe4/0x208 [] vfs_write+0xbc/0x160 [] SyS_write+0x54/0xd8 [] 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 Commit 356c05d58af05d582e634b54b40050c73609617b 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 Acked-by: Alan Stern Cc: Eric W. Biederman Cc: Tejun Heo Cc: Peter Zijlstra Cc: Greg Kroah-Hartman Signed-off-by: Wolfram Sang --- drivers/i2c/i2c-core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index 6b63cc7eb71e..48e31ed69dbf 100644 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -892,7 +892,8 @@ i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr, } static DEVICE_ATTR(new_device, S_IWUSR, NULL, i2c_sysfs_new_device); -static DEVICE_ATTR(delete_device, S_IWUSR, NULL, i2c_sysfs_delete_device); +static DEVICE_ATTR_IGNORE_LOCKDEP(delete_device, S_IWUSR, NULL, + i2c_sysfs_delete_device); static struct attribute *i2c_adapter_attrs[] = { &dev_attr_name.attr, -- 2.30.2