possible recursive locking detected when doing fsi rescan

[shenki]

root@spork-bmc:~# echo 1 > /sys/class/fsi-master/fsi0/rescan 
[ 5391.476549] 
[ 5391.478235] ============================================
[ 5391.484171] WARNING: possible recursive locking detected
[ 5391.490109] 5.4.32-00259-g49233ddf638c-dirty #169 Not tainted
[ 5391.496527] --------------------------------------------
[ 5391.502478] sh/381 is trying to acquire lock:
[ 5391.507350] b58116e8 (&master->scan_lock){+.+.}, at: fsi_master_unregister+0x44/0x70
[ 5391.516023] 
[ 5391.516023] but task is already holding lock:
[ 5391.522536] bc8c3f28 (&master->scan_lock){+.+.}, at: fsi_master_rescan+0x28/0x58
[ 5391.530805] 
[ 5391.530805] other info that might help us debug this:
[ 5391.538088]  Possible unsafe locking scenario:
[ 5391.538088] 
[ 5391.544692]        CPU0
[ 5391.547417]        ----
[ 5391.550141]   lock(&master->scan_lock);
[ 5391.554420]   lock(&master->scan_lock);
[ 5391.558700] 
[ 5391.558700]  *** DEADLOCK ***
[ 5391.558700] 
[ 5391.565305]  May be due to missing lock nesting notation
[ 5391.565305] 
[ 5391.572881] 5 locks held by sh/381:
[ 5391.576770]  #0: b46fb270 (sb_writers#5){.+.+}, at: vfs_write+0x15c/0x18c
[ 5391.584360]  #1: b4906404 (&of->mutex){+.+.}, at: kernfs_fop_write+0xf8/0x264
[ 5391.592335]  #2: bc8c0f78 (kn->count#150){.+.+}, at: kernfs_fop_write+0x100/0x264
[ 5391.600698]  #3: bc8c3f28 (&master->scan_lock){+.+.}, at: fsi_master_rescan+0x28/0x58
[ 5391.609446]  #4: b57df8bc (&dev->mutex){....}, at: __device_driver_lock+0x3c/0x50
[ 5391.617809] 
[ 5391.617809] stack backtrace:
[ 5391.622673] CPU: 1 PID: 381 Comm: sh Not tainted 5.4.32-00259-g49233ddf638c-dirty #169
[ 5391.631508] Hardware name: Generic DT based system
[ 5391.636852] Backtrace: 
[ 5391.639590] [<8010f384>] (dump_backtrace) from [<8010f5b8>] (show_stack+0x20/0x24)
[ 5391.648042]  r7:00000080 r6:60000093 r5:00000000 r4:80e7052c
[ 5391.654353] [<8010f598>] (show_stack) from [<8092ba74>] (dump_stack+0xe0/0x114)
[ 5391.662516] [<8092b994>] (dump_stack) from [<80189874>] (__lock_acquire+0x7ec/0x253c)
[ 5391.671257]  r7:bc94f200 r6:bc94f780 r5:812fce44 r4:812fce44
[ 5391.677576] [<80189088>] (__lock_acquire) from [<8018bea4>] (lock_acquire+0xd0/0x27c)
[ 5391.686321]  r10:60000013 r9:8148fdc0 r8:00000000 r7:00000000 r6:00000000 r5:00000000
[ 5391.695061]  r4:b58116e8
[ 5391.697893] [<8018bdd4>] (lock_acquire) from [<80948fc8>] (__mutex_lock+0xa8/0xabc)
[ 5391.706443]  r10:00000051 r9:8148fdc0 r8:bd154000 r7:00000000 r6:00000000 r5:00000000
[ 5391.715182]  r4:b58116b4
[ 5391.718012] [<80948f20>] (__mutex_lock) from [<8094acd0>] (mutex_lock_nested+0x2c/0x34)
[ 5391.726949]  r10:00000051 r9:b581f400 r8:bd154000 r7:00000000 r6:80e64610 r5:b58116b4
[ 5391.735687]  r4:b5811400
[ 5391.738515] [<8094aca4>] (mutex_lock_nested) from [<8075a9b8>] (fsi_master_unregister+0x44/0x70)
[ 5391.748332] [<8075a974>] (fsi_master_unregister) from [<8075aa58>] (hub_master_remove+0x20/0x44)
[ 5391.758139]  r5:00000000 r4:b5811400
[ 5391.762134] [<8075aa38>] (hub_master_remove) from [<805d291c>] (device_release_driver_internal+0xfc/0x1b4)
[ 5391.772910]  r5:00000000 r4:b57df800
[ 5391.776903] [<805d2820>] (device_release_driver_internal) from [<805d29f4>] (device_release_driver+0x20/0x24)
[ 5391.787971]  r7:00000000 r6:80e64160 r5:b57df800 r4:bd3eec4c
[ 5391.794289] [<805d29d4>] (device_release_driver) from [<805d0368>] (bus_remove_device+0xe0/0x148)
[ 5391.804199] [<805d0288>] (bus_remove_device) from [<805ccb18>] (device_del+0x14c/0x398)
[ 5391.813134]  r7:00000000 r6:bd154000 r5:b57df888 r4:b57df800
[ 5391.819454] [<805cc9cc>] (device_del) from [<805ccd88>] (device_unregister+0x24/0x6c)
[ 5391.828197]  r10:00000051 r9:bd155f60 r8:019fb498 r7:00000000 r6:bd154000 r5:807584cc
[ 5391.836937]  r4:b57df800
[ 5391.839775] [<805ccd64>] (device_unregister) from [<807584e4>] (fsi_slave_remove_device+0x18/0x20)
[ 5391.849778]  r5:807584cc r4:00000000
[ 5391.853772] [<807584cc>] (fsi_slave_remove_device) from [<805cd210>] (device_for_each_child+0x70/0xa8)
[ 5391.864165] [<805cd1a0>] (device_for_each_child) from [<807584ac>] (fsi_master_remove_slave+0x24/0x44)
[ 5391.874555]  r7:b49063c0 r6:bd154000 r5:80758488 r4:b581f400
[ 5391.880874] [<80758488>] (fsi_master_remove_slave) from [<805cd210>] (device_for_each_child+0x70/0xa8)
[ 5391.891264]  r5:80758488 r4:00000000
[ 5391.895258] [<805cd1a0>] (device_for_each_child) from [<8075a84c>] (fsi_master_rescan+0x38/0x58)
[ 5391.905065]  r7:b49063c0 r6:b717abc0 r5:bc8c3ef4 r4:bc8c3c40
[ 5391.911385] [<8075a814>] (fsi_master_rescan) from [<8075a888>] (master_rescan_store+0x1c/0x28)
[ 5391.920996]  r5:805caca8 r4:00000002
[ 5391.924989] [<8075a86c>] (master_rescan_store) from [<805caccc>] (dev_attr_store+0x24/0x30)
[ 5391.934310]  r5:805caca8 r4:8075a86c
[ 5391.938304] [<805caca8>] (dev_attr_store) from [<80380a98>] (sysfs_kf_write+0x50/0x5c)
[ 5391.947140]  r5:805caca8 r4:00000002
[ 5391.951132] [<80380a48>] (sysfs_kf_write) from [<80380058>] (kernfs_fop_write+0x134/0x264)
[ 5391.960358]  r7:b49063c0 r6:b49063d0 r5:00000000 r4:00000000
[ 5391.966678] [<8037ff24>] (kernfs_fop_write) from [<802e79cc>] (__vfs_write+0x4c/0x1dc)
[ 5391.975518]  r10:00000004 r9:00000000 r8:8037ff24 r7:00000002 r6:bd155f60 r5:bd154000
[ 5391.984255]  r4:b49bb780
[ 5391.987083] [<802e7980>] (__vfs_write) from [<802e96f8>] (vfs_write+0xbc/0x18c)
[ 5391.995245]  r10:00000004 r9:00000000 r8:00000000 r7:bd155f60 r6:019fb498 r5:b49bb780
[ 5392.003984]  r4:00000002
[ 5392.006812] [<802e963c>] (vfs_write) from [<802e9998>] (ksys_write+0x74/0xec)
[ 5392.014779]  r8:00000000 r7:00000002 r6:bd154000 r5:b49bb780 r4:b49bb780
[ 5392.022261] [<802e9924>] (ksys_write) from [<802e9a28>] (sys_write+0x18/0x1c)
[ 5392.030228]  r9:bd154000 r8:801011c4 r7:00000004 r6:76fb3260 r5:019fb498 r4:00000002
[ 5392.038867] [<802e9a10>] (sys_write) from [<80101000>] (ret_fast_syscall+0x0/0x28)
[ 5392.047316] Exception stack(0xbd155fa8 to 0xbd155ff0)
[ 5392.052957] 5fa0:                   00000002 019fb498 00000001 019fb498 00000002 00000000
[ 5392.062088] 5fc0: 00000002 019fb498 76fb3260 00000004 76f41124 76f40c8c 00000000 00000000
[ 5392.071216] 5fe0: 00000498 7eb899f8 76e6c1cc 76ec6c10

[mdmillerii]

I seem to remember some deferral infrastructure, probably for scsi or usb, but will search later.