From mboxrd@z Thu Jan 1 00:00:00 1970 From: balbi@ti.com (Felipe Balbi) Date: Wed, 8 Feb 2012 14:41:48 +0200 Subject: Possible circular locking dependency (3.3-rc2) Message-ID: <20120208124147.GF16334@legolas.emea.dhcp.ti.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi guys, I have just triggered the folllowing: [ 84.860321] ====================================================== [ 84.860321] [ INFO: possible circular locking dependency detected ] [ 84.860321] 3.3.0-rc2-00026-ge4e8a39 #474 Not tainted [ 84.860321] ------------------------------------------------------- [ 84.860321] bash/949 is trying to acquire lock: [ 84.860321] (sysfs_lock){+.+.+.}, at: [] gpio_value_store+0x24/0xcc [ 84.860321] [ 84.860321] but task is already holding lock: [ 84.860321] (s_active#22){++++.+}, at: [] sysfs_write_file+0xdc/0x184 [ 84.911468] [ 84.911468] which lock already depends on the new lock. [ 84.911468] [ 84.920043] [ 84.920043] the existing dependency chain (in reverse order) is: [ 84.920043] [ 84.927886] -> #1 (s_active#22){++++.+}: [ 84.927886] [] check_prevs_add+0xdc/0x150 [ 84.927886] [] validate_chain.clone.24+0x564/0x694 [ 84.927886] [] __lock_acquire+0x49c/0x980 [ 84.951660] [] lock_acquire+0x98/0x100 [ 84.951660] [] sysfs_deactivate+0xb0/0x100 [ 84.962982] [] sysfs_addrm_finish+0x2c/0x6c [ 84.962982] [] sysfs_remove_dir+0x84/0x98 [ 84.962982] [] kobject_del+0x10/0x78 [ 84.974670] [] device_del+0x140/0x170 [ 84.974670] [] device_unregister+0xc/0x18 [ 84.985382] [] gpio_unexport+0xbc/0xdc [ 84.985382] [] gpio_free+0x14/0xfc [ 85.001708] [] unexport_store+0x78/0x8c [ 85.001708] [] class_attr_store+0x18/0x24 [ 85.007293] [] sysfs_write_file+0x100/0x184 [ 85.018981] [] vfs_write+0xb4/0x148 [ 85.018981] [] sys_write+0x40/0x70 [ 85.018981] [] ret_fast_syscall+0x0/0x3c [ 85.035003] [ 85.035003] -> #0 (sysfs_lock){+.+.+.}: [ 85.035003] [] check_prev_add+0x680/0x698 [ 85.035003] [] check_prevs_add+0xdc/0x150 [ 85.052093] [] validate_chain.clone.24+0x564/0x694 [ 85.052093] [] __lock_acquire+0x49c/0x980 [ 85.052093] [] lock_acquire+0x98/0x100 [ 85.069885] [] mutex_lock_nested+0x3c/0x2f4 [ 85.069885] [] gpio_value_store+0x24/0xcc [ 85.069885] [] dev_attr_store+0x18/0x24 [ 85.087158] [] sysfs_write_file+0x100/0x184 [ 85.087158] [] vfs_write+0xb4/0x148 [ 85.098297] [] sys_write+0x40/0x70 [ 85.098297] [] ret_fast_syscall+0x0/0x3c [ 85.109069] [ 85.109069] other info that might help us debug this: [ 85.109069] [ 85.117462] Possible unsafe locking scenario: [ 85.117462] [ 85.117462] CPU0 CPU1 [ 85.128417] ---- ---- [ 85.128417] lock(s_active#22); [ 85.128417] lock(sysfs_lock); [ 85.128417] lock(s_active#22); [ 85.142486] lock(sysfs_lock); [ 85.151794] [ 85.151794] *** DEADLOCK *** [ 85.151794] [ 85.151794] 2 locks held by bash/949: [ 85.158020] #0: (&buffer->mutex){+.+.+.}, at: [] sysfs_write_file+0x28/0x184 [ 85.170349] #1: (s_active#22){++++.+}, at: [] sysfs_write_file+0xdc/0x184 [ 85.170349] [ 85.178588] stack backtrace: [ 85.178588] [] (unwind_backtrace+0x0/0xf0) from [] (print_circular_bug+0x100/0x114) [ 85.193023] [] (print_circular_bug+0x100/0x114) from [] (check_prev_add+0x680/0x698) [ 85.193023] [] (check_prev_add+0x680/0x698) from [] (check_prevs_add+0xdc/0x150) [ 85.212524] [] (check_prevs_add+0xdc/0x150) from [] (validate_chain.clone.24+0x564/0x694) [ 85.212524] [] (validate_chain.clone.24+0x564/0x694) from [] (__lock_acquire+0x49c/0x980) [ 85.233306] [] (__lock_acquire+0x49c/0x980) from [] (lock_acquire+0x98/0x100) [ 85.233306] [] (lock_acquire+0x98/0x100) from [] (mutex_lock_nested+0x3c/0x2f4) [ 85.242614] [] (mutex_lock_nested+0x3c/0x2f4) from [] (gpio_value_store+0x24/0xcc) [ 85.261840] [] (gpio_value_store+0x24/0xcc) from [] (dev_attr_store+0x18/0x24) [ 85.261840] [] (dev_attr_store+0x18/0x24) from [] (sysfs_write_file+0x100/0x184) [ 85.271240] [] (sysfs_write_file+0x100/0x184) from [] (vfs_write+0xb4/0x148) [ 85.290008] [] (vfs_write+0xb4/0x148) from [] (sys_write+0x40/0x70) [ 85.298400] [] (sys_write+0x40/0x70) from [] (ret_fast_syscall+0x0/0x3c) -bash: echo: write error: Operation not permitted the way to trigger is: root at legolas:~# cd /sys/class/gpio/ root at legolas:/sys/class/gpio# echo 2 > export root at legolas:/sys/class/gpio# echo 2 > unexport root at legolas:/sys/class/gpio# echo 2 > export root at legolas:/sys/class/gpio# cd gpio2/ root at legolas:/sys/class/gpio/gpio2# echo 1 > value -- balbi -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 836 bytes Desc: Digital signature URL: