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Hi, On Wed, Feb 8, 2012 at 8:41 PM, Felipe Balbi <balbi@ti.com> wrote: > 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: [<c0275358>] gpio_value_store+0x24/0xcc > [ 84.860321] > [ 84.860321] but task is already holding lock: > [ 84.860321] (s_active#22){++++.+}, at: [<c016996c>] 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] [<c008f640>] check_prevs_add+0xdc/0x150 > [ 84.927886] [<c008fc18>] validate_chain.clone.24+0x564/0x694 > [ 84.927886] [<c0090cdc>] __lock_acquire+0x49c/0x980 > [ 84.951660] [<c0091838>] lock_acquire+0x98/0x100 > [ 84.951660] [<c016a8e8>] sysfs_deactivate+0xb0/0x100 > [ 84.962982] [<c016b1b4>] sysfs_addrm_finish+0x2c/0x6c > [ 84.962982] [<c016b8bc>] sysfs_remove_dir+0x84/0x98 > [ 84.962982] [<c02590d8>] kobject_del+0x10/0x78 > [ 84.974670] [<c02c29e8>] device_del+0x140/0x170 > [ 84.974670] [<c02c2a24>] device_unregister+0xc/0x18 > [ 84.985382] [<c0276894>] gpio_unexport+0xbc/0xdc > [ 84.985382] [<c02768c8>] gpio_free+0x14/0xfc > [ 85.001708] [<c0276a28>] unexport_store+0x78/0x8c > [ 85.001708] [<c02c5af8>] class_attr_store+0x18/0x24 > [ 85.007293] [<c0169990>] sysfs_write_file+0x100/0x184 > [ 85.018981] [<c0109d48>] vfs_write+0xb4/0x148 > [ 85.018981] [<c0109fd0>] sys_write+0x40/0x70 > [ 85.018981] [<c0013cc0>] ret_fast_syscall+0x0/0x3c > [ 85.035003] > [ 85.035003] -> #0 (sysfs_lock){+.+.+.}: > [ 85.035003] [<c008f54c>] check_prev_add+0x680/0x698 > [ 85.035003] [<c008f640>] check_prevs_add+0xdc/0x150 > [ 85.052093] [<c008fc18>] validate_chain.clone.24+0x564/0x694 > [ 85.052093] [<c0090cdc>] __lock_acquire+0x49c/0x980 > [ 85.052093] [<c0091838>] lock_acquire+0x98/0x100 > [ 85.069885] [<c047e280>] mutex_lock_nested+0x3c/0x2f4 > [ 85.069885] [<c0275358>] gpio_value_store+0x24/0xcc > [ 85.069885] [<c02c18dc>] dev_attr_store+0x18/0x24 > [ 85.087158] [<c0169990>] sysfs_write_file+0x100/0x184 > [ 85.087158] [<c0109d48>] vfs_write+0xb4/0x148 > [ 85.098297] [<c0109fd0>] sys_write+0x40/0x70 > [ 85.098297] [<c0013cc0>] 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: [<c01698b8>] sysfs_write_file+0x28/0x184 > [ 85.170349] #1: (s_active#22){++++.+}, at: [<c016996c>] sysfs_write_file+0xdc/0x184 > [ 85.170349] > [ 85.178588] stack backtrace: > [ 85.178588] [<c001b824>] (unwind_backtrace+0x0/0xf0) from [<c008de64>] (print_circular_bug+0x100/0x114) > [ 85.193023] [<c008de64>] (print_circular_bug+0x100/0x114) from [<c008f54c>] (check_prev_add+0x680/0x698) > [ 85.193023] [<c008f54c>] (check_prev_add+0x680/0x698) from [<c008f640>] (check_prevs_add+0xdc/0x150) > [ 85.212524] [<c008f640>] (check_prevs_add+0xdc/0x150) from [<c008fc18>] (validate_chain.clone.24+0x564/0x694) > [ 85.212524] [<c008fc18>] (validate_chain.clone.24+0x564/0x694) from [<c0090cdc>] (__lock_acquire+0x49c/0x980) > [ 85.233306] [<c0090cdc>] (__lock_acquire+0x49c/0x980) from [<c0091838>] (lock_acquire+0x98/0x100) > [ 85.233306] [<c0091838>] (lock_acquire+0x98/0x100) from [<c047e280>] (mutex_lock_nested+0x3c/0x2f4) > [ 85.242614] [<c047e280>] (mutex_lock_nested+0x3c/0x2f4) from [<c0275358>] (gpio_value_store+0x24/0xcc) > [ 85.261840] [<c0275358>] (gpio_value_store+0x24/0xcc) from [<c02c18dc>] (dev_attr_store+0x18/0x24) > [ 85.261840] [<c02c18dc>] (dev_attr_store+0x18/0x24) from [<c0169990>] (sysfs_write_file+0x100/0x184) > [ 85.271240] [<c0169990>] (sysfs_write_file+0x100/0x184) from [<c0109d48>] (vfs_write+0xb4/0x148) > [ 85.290008] [<c0109d48>] (vfs_write+0xb4/0x148) from [<c0109fd0>] (sys_write+0x40/0x70) > [ 85.298400] [<c0109fd0>] (sys_write+0x40/0x70) from [<c0013cc0>] (ret_fast_syscall+0x0/0x3c) > -bash: echo: write error: Operation not permitted > > the way to trigger is: > > root@legolas:~# cd /sys/class/gpio/ > root@legolas:/sys/class/gpio# echo 2 > export > root@legolas:/sys/class/gpio# echo 2 > unexport > root@legolas:/sys/class/gpio# echo 2 > export > root@legolas:/sys/class/gpio# cd gpio2/ > root@legolas:/sys/class/gpio/gpio2# echo 1 > value Looks 'sysfs_lock' needn't to be held for unregister, so the patch below may fix the problem. Acked-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Grant Likely <grant.likely@secretlab.ca> |
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|---|---|---|
| .. | ||
| devres.c | ||
| gpio-74x164.c | ||
| gpio-ab8500.c | ||
| gpio-adp5520.c | ||
| gpio-adp5588.c | ||
| gpio-bt8xx.c | ||
| gpio-cs5535.c | ||
| gpio-da9052.c | ||
| gpio-davinci.c | ||
| gpio-ep93xx.c | ||
| gpio-generic.c | ||
| gpio-it8761e.c | ||
| gpio-janz-ttl.c | ||
| gpio-ks8695.c | ||
| gpio-langwell.c | ||
| gpio-lpc32xx.c | ||
| gpio-max730x.c | ||
| gpio-max732x.c | ||
| gpio-max7300.c | ||
| gpio-max7301.c | ||
| gpio-mc9s08dz60.c | ||
| gpio-mc33880.c | ||
| gpio-mcp23s08.c | ||
| gpio-ml-ioh.c | ||
| gpio-mpc8xxx.c | ||
| gpio-mpc5200.c | ||
| gpio-msm-v1.c | ||
| gpio-msm-v2.c | ||
| gpio-mxc.c | ||
| gpio-mxs.c | ||
| gpio-nomadik.c | ||
| gpio-omap.c | ||
| gpio-pca953x.c | ||
| gpio-pcf857x.c | ||
| gpio-pch.c | ||
| gpio-pl061.c | ||
| gpio-pxa.c | ||
| gpio-rdc321x.c | ||
| gpio-sa1100.c | ||
| gpio-samsung.c | ||
| gpio-sch.c | ||
| gpio-sodaville.c | ||
| gpio-stmpe.c | ||
| gpio-sx150x.c | ||
| gpio-tc3589x.c | ||
| gpio-tegra.c | ||
| gpio-timberdale.c | ||
| gpio-tnetv107x.c | ||
| gpio-tps65910.c | ||
| gpio-tps65912.c | ||
| gpio-twl4030.c | ||
| gpio-ucb1400.c | ||
| gpio-vr41xx.c | ||
| gpio-vx855.c | ||
| gpio-wm831x.c | ||
| gpio-wm8350.c | ||
| gpio-wm8994.c | ||
| gpio-xilinx.c | ||
| gpiolib.c | ||
| Kconfig | ||
| Makefile | ||