sysfs lockdep complaint

From: Johannes Berg
Date: Thu Feb 18 2010 - 04:32:31 EST


Get this when powernowd starts on my G5:

[ 30.490674] =============================================
[ 30.490708] [ INFO: possible recursive locking detected ]
[ 30.490727] 2.6.33-rc8-wl-64012-g6917413 #160
[ 30.490744] ---------------------------------------------
[ 30.490763] powernowd/2577 is trying to acquire lock:
[ 30.490782] (s_active){++++.+}, at: [<c0000000001efa94>] .sysfs_addrm_finish+0x58/0xc0
[ 30.490831]
[ 30.490833] but task is already holding lock:
[ 30.490854] (s_active){++++.+}, at: [<c0000000001eff80>] .sysfs_get_active_two+0x3c/0x84
[ 30.490895]
[ 30.490896] other info that might help us debug this:
[ 30.490921] 4 locks held by powernowd/2577:
[ 30.490936] #0: (&buffer->mutex){+.+.+.}, at: [<c0000000001ed8d0>] .sysfs_write_file+0x60/0x1a4
[ 30.490983] #1: (s_active){++++.+}, at: [<c0000000001eff80>] .sysfs_get_active_two+0x3c/0x84
[ 30.491028] #2: (s_active){++++.+}, at: [<c0000000001eff98>] .sysfs_get_active_two+0x54/0x84
[ 30.491073] #3: (dbs_mutex){+.+.+.}, at: [<d000000002c9c6e8>] .cpufreq_governor_dbs+0x424/0x548 [cpufreq_ondemand]
[ 30.491128]
[ 30.491130] stack backtrace:
[ 30.491148] Call Trace:
[ 30.491166] [c00000021251af10] [c000000000012934] .show_stack+0xc0/0x200 (unreliable)
[ 30.491205] [c00000021251afe0] [c0000000005a74b0] .dump_stack+0x28/0x3c
[ 30.491234] [c00000021251b060] [c0000000000b88c8] .validate_chain+0x758/0x1044
[ 30.491265] [c00000021251b1a0] [c0000000000b9b94] .__lock_acquire+0x9e0/0xac4
[ 30.491294] [c00000021251b2d0] [c0000000000b9dc8] .lock_acquire+0x150/0x19c
[ 30.491324] [c00000021251b3a0] [c0000000001eeeb8] .sysfs_deactivate+0xd0/0x16c
[ 30.491354] [c00000021251b4f0] [c0000000001efa94] .sysfs_addrm_finish+0x58/0xc0
[ 30.491385] [c00000021251b590] [c0000000001ecb98] .sysfs_hash_and_remove+0x7c/0xb0
[ 30.491416] [c00000021251b640] [c0000000001f1710] .sysfs_remove_group+0xb4/0x138
[ 30.491450] [c00000021251b6e0] [d000000002c9c6f8] .cpufreq_governor_dbs+0x434/0x548 [cpufreq_ondemand]
[ 30.491487] [c00000021251b7e0] [c0000000004cc3e4] .__cpufreq_governor+0x1cc/0x250
[ 30.491520] [c00000021251b890] [c0000000004cdb90] .__cpufreq_set_policy+0x1f8/0x2a8
[ 30.491552] [c00000021251b940] [c0000000004ce1a0] .store_scaling_governor+0x1c0/0x21c
[ 30.491584] [c00000021251bb50] [c0000000004cd954] .store+0x98/0xdc
[ 30.491611] [c00000021251bc00] [c0000000001ed9a4] .sysfs_write_file+0x134/0x1a4
[ 30.491644] [c00000021251bcc0] [c000000000176ca0] .vfs_write+0xe8/0x1fc
[ 30.491672] [c00000021251bd70] [c000000000176ef0] .SyS_write+0x68/0xb0
[ 30.491700] [c00000021251be30] [c0000000000075d4] syscall_exit+0x0/0x40


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