From: Alexander Stein <alexander.stein@systec-electronic.com>
To: linux-kernel@vger.kernel.org
Cc: Grant Likely <grant.likely@secretlab.ca>
Subject: gpiolib.c: possible circular locking dependency detected
Date: Mon, 11 Jul 2011 14:19:55 +0200 [thread overview]
Message-ID: <201107111419.55719.alexander.stein@systec-electronic.com> (raw)
Hello,
I used a shell script using /sys/class/gpio to export,set/unset and unexport
GPIOs. Upon unexporting GPIOs I get the dmesg shown below. I didn't find any
important change in gpiolib.c and fs/sysfs/dir.c between 2.6.39 and git master
which would fix this.
Has somebody an idea about this?
Regards,
Alexander
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.39+ #5
-------------------------------------------------------
gpio.sh/765 is trying to acquire lock:
(s_active#40){++++.+}, at: [<c10d566d>] sysfs_addrm_finish+0x27/0x4a
but task is already holding lock:
(sysfs_lock){+.+.+.}, at: [<c11664a8>] gpio_unexport+0x27/0x77
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (sysfs_lock){+.+.+.}:
[<c104f517>] validate_chain.clone.14+0x425/0x518
[<c10504d8>] __lock_acquire+0x653/0x6bb
[<c1050945>] lock_acquire+0x63/0x7b
[<c130b9e8>] mutex_lock_nested+0x45/0x291
[<c1166261>] gpio_direction_store+0x20/0xab
[<c11bf5e9>] dev_attr_store+0x22/0x27
[<c10d4684>] sysfs_write_file+0xb6/0xe9
[<c1094841>] vfs_write+0x91/0x10d
[<c1094a69>] sys_write+0x3e/0x63
[<c130da4c>] sysenter_do_call+0x12/0x32
-> #0 (s_active#40){++++.+}:
[<c104ecea>] check_prev_add+0xd5/0x4dd
[<c104f517>] validate_chain.clone.14+0x425/0x518
[<c10504d8>] __lock_acquire+0x653/0x6bb
[<c1050945>] lock_acquire+0x63/0x7b
[<c10d509e>] sysfs_deactivate+0x85/0xba
[<c10d566d>] sysfs_addrm_finish+0x27/0x4a
[<c10d5ac2>] sysfs_remove_dir+0x5f/0x6d
[<c115594d>] kobject_del+0xf/0x5e
[<c11c01bd>] device_del+0x12e/0x13a
[<c11c01d4>] device_unregister+0xb/0x15
[<c11664e9>] gpio_unexport+0x68/0x77
[<c1166514>] gpio_free+0x1c/0xa3
[<c11665df>] unexport_store+0x44/0x49
[<c11c29ec>] class_attr_store+0x25/0x2a
[<c10d4684>] sysfs_write_file+0xb6/0xe9
[<c1094841>] vfs_write+0x91/0x10d
[<c1094a69>] sys_write+0x3e/0x63
[<c130da4c>] sysenter_do_call+0x12/0x32
other info that might help us debug this:
3 locks held by gpio.sh/765:
#0: (&buffer->mutex){+.+.+.}, at: [<c10d45f3>] sysfs_write_file+0x25/0xe9
#1: (s_active#52){.+.+.+}, at: [<c10d4669>] sysfs_write_file+0x9b/0xe9
#2: (sysfs_lock){+.+.+.}, at: [<c11664a8>] gpio_unexport+0x27/0x77
stack backtrace:
Pid: 765, comm: gpio.sh Not tainted 2.6.39+ #5
Call Trace:
[<c130a450>] ? printk+0x19/0x1b
[<c104e2c6>] print_circular_bug+0x94/0x9d
[<c104ecea>] check_prev_add+0xd5/0x4dd
[<c104f517>] validate_chain.clone.14+0x425/0x518
[<c104fc9c>] ? mark_lock+0x208/0x2d7
[<c10504d8>] __lock_acquire+0x653/0x6bb
[<c104d433>] ? lockdep_init_map+0x8a/0x3c3
[<c1051079>] ? trace_hardirqs_on+0xb/0xd
[<c1050945>] lock_acquire+0x63/0x7b
[<c10d566d>] ? sysfs_addrm_finish+0x27/0x4a
[<c10d509e>] sysfs_deactivate+0x85/0xba
[<c10d566d>] ? sysfs_addrm_finish+0x27/0x4a
[<c10d566d>] sysfs_addrm_finish+0x27/0x4a
[<c10d5ac2>] sysfs_remove_dir+0x5f/0x6d
[<c115594d>] kobject_del+0xf/0x5e
[<c11c01bd>] device_del+0x12e/0x13a
[<c11c01d4>] device_unregister+0xb/0x15
[<c11664e9>] gpio_unexport+0x68/0x77
[<c1165417>] ? gpio_set_value_cansleep+0x1c/0x1c
[<c116659b>] ? gpio_free+0xa3/0xa3
[<c1166514>] gpio_free+0x1c/0xa3
[<c116659b>] ? gpio_free+0xa3/0xa3
[<c11665df>] unexport_store+0x44/0x49
[<c11c29ec>] class_attr_store+0x25/0x2a
[<c10d4684>] sysfs_write_file+0xb6/0xe9
[<c1094841>] vfs_write+0x91/0x10d
[<c10d45ce>] ? sysfs_poll+0x72/0x72
[<c1094a69>] sys_write+0x3e/0x63
[<c130da4c>] sysenter_do_call+0x12/0x32
next reply other threads:[~2011-07-11 12:27 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-11 12:19 Alexander Stein [this message]
2011-07-15 20:15 ` Grant Likely
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