Re: [PATCH 1/3] pwm: core: Rearrange pwm lock.
On Wed, Dec 18, 2013 at 05:06:53PM +0530, Sourav Poddar wrote:
When tiecap is used as a module, then while doing a rmmod I
get the following dump.
root@am437x-evm:/# rmmod pwm_tiecap
[ 219.539245]
[ 219.540771] ==
[ 219.546936] [ INFO: possible circular locking dependency detected ]
[ 219.553192] 3.12.4-01557-g9921cde-dirty #134 Not tainted
[ 219.558471] ---
[ 219.564727] rmmod/1517 is trying to acquire lock:
[ 219.569427] (s_active#35){.+}, at: [c017ab00]
sysfs_hash_and_remove+0x4c/0x8c
[ 219.577239]
[ 219.577239] but task is already holding lock:
[ 219.583068] (pwm_lock){+.+.+.}, at: [c0303598] pwmchip_remove+0x14/0xf8
[ 219.589996]
[ 219.589996] which lock already depends on the new lock.
[ 219.589996]
[ 219.598144]
[ 219.598144] the existing dependency chain (in reverse order) is:
[ 219.605590]
- #1 (pwm_lock){+.+.+.}:
[ 219.609497][c00a2d1c] lock_acquire+0x9c/0x128
[ 219.614746][c0639bc0] mutex_lock_nested+0x50/0x3dc
[ 219.620391][c0303974] pwm_request_from_chip+0x38/0x6c
[ 219.626312][c0303fe0] pwm_export_store+0x50/0x140
[ 219.631896][c039aba8] dev_attr_store+0x18/0x24
[ 219.637207][c017aff0] sysfs_write_file+0x16c/0x1a0
[ 219.642883][c0119084] vfs_write+0xb0/0x188
[ 219.647857][c0119478] SyS_write+0x3c/0x70
[ 219.652770][c0014100] ret_fast_syscall+0x0/0x48
[ 219.658172]
- #0 (s_active#35){.+}:
[ 219.662353][c00a2778] __lock_acquire+0x1b28/0x1b70
[ 219.667999][c00a2d1c] lock_acquire+0x9c/0x128
[ 219.673248][c017c780] sysfs_addrm_finish+0xe8/0x158
[ 219.678985][c017ab00] sysfs_hash_and_remove+0x4c/0x8c
[ 219.684906][c017e224] remove_files+0x38/0x74
[ 219.690063][c017e2a4] sysfs_remove_group+0x44/0x108
[ 219.695800][c017e38c] sysfs_remove_groups+0x24/0x34
[ 219.701538][c039bc2c] device_del+0xec/0x178
[ 219.706604][c039bcc4] device_unregister+0xc/0x18
[ 219.712097][c0303658] pwmchip_remove+0xd4/0xf8
[ 219.717407][c039fdc4] platform_drv_remove+0x18/0x1c
[ 219.723175][c039e6c4] __device_release_driver+0x70/0xc8
[ 219.729248][c039eec8] driver_detach+0xb4/0xb8
[ 219.734497][c039e4ec] bus_remove_driver+0x8c/0xd0
[ 219.740081][c00abd2c] SyS_delete_module+0x118/0x22c
[ 219.745819][c0014100] ret_fast_syscall+0x0/0x48
[ 219.751220]
[ 219.751220] other info that might help us debug this:
[ 219.751220]
[ 219.759216] Possible unsafe locking scenario:
[ 219.759216]
[ 219.765106]CPU0CPU1
[ 219.769622]
[ 219.774139] lock(pwm_lock);
[ 219.777130]lock(s_active#35);
[ 219.782897]lock(pwm_lock);
[ 219.788391] lock(s_active#35);
[ 219.791656]
[ 219.791656] *** DEADLOCK ***
[ 219.791656]
[ 219.797546] 3 locks held by rmmod/1517:
[ 219.801391] #0: (__lockdep_no_validate__){..}, at: [c039ee58]
driver_detach+0x44/0xb8
[ 219.810028] #1: (__lockdep_no_validate__){..}, at: [c039ee64]
driver_detach+0x50/0xb8
[ 219.818695] #2: (pwm_lock){+.+.+.}, at: [c0303598]
pwmchip_remove+0x14/0xf8
[ 219.826049]
[ 219.826049] stack backtrace:
[ 219.830413] CPU: 0 PID: 1517 Comm: rmmod Not tainted
3.12.4-01557-g9921cde-dirty #134
[ 219.838256] [c001cc98] (unwind_backtrace+0x0/0xf0) from [c0018124]
(show_stack+0x10/0x14)
[ 219.846771] [c0018124] (show_stack+0x10/0x14) from [c0636728]
(dump_stack+0x74/0xb4)
[ 219.854858] [c0636728] (dump_stack+0x74/0xb4) from [c06344e4]
(print_circular_bug+0x284/0x2d8)
[ 219.863830] [c06344e4] (print_circular_bug+0x284/0x2d8) from
[c00a2778] (__lock_acquire+0x1b28/0x1b70)
[ 219.873443] [c00a2778] (__lock_acquire+0x1b28/0x1b70) from [c00a2d1c]
(lock_acquire+0x9c/0x128)
[ 219.882476] [c00a2d1c] (lock_acquire+0x9c/0x128) from [c017c780]
(sysfs_addrm_finish+0xe8/0x158)
[ 219.891601] [c017c780] (sysfs_addrm_finish+0xe8/0x158) from [c017ab00]
(sysfs_hash_and_remove+0x4c/0x8c)
[ 219.901397] [c017ab00] (sysfs_hash_and_remove+0x4c/0x8c) from
[c017e224] (remove_files+0x38/0x74)
[ 219.910614] [c017e224] (remove_files+0x38/0x74) from [c017e2a4]
(sysfs_remove_group+0x44/0x108)
[ 219.919647] [c017e2a4] (sysfs_remove_group+0x44/0x108) from [c017e38c]
(sysfs_remove_groups+0x24/0x34)
[ 219.929260] [c017e38c] (sysfs_remove_groups+0x24/0x34) from [c039bc2c]
(device_del+0xec/0x178)
[ 219.938201] [c039bc2c] (device_del+0xec/0x178) from [c039bcc4]
(device_unregister+0xc/0x18)
[ 219.946899] [c039bcc4] (device_unregister+0xc/0x18) from [c0303658]
(pwmchip_remove+0xd4/0xf8)
[ 219.955841] [c0303658] (pwmchip_remove+0xd4/0xf8) from [c039fdc4]
(platform_drv_remove+0x18/0x1c)
[ 219.965057]
[PATCH 1/3] pwm: core: Rearrange pwm lock.
When tiecap is used as a module, then while doing a rmmod I
get the following dump.
root@am437x-evm:/# rmmod pwm_tiecap
[ 219.539245]
[ 219.540771] ==
[ 219.546936] [ INFO: possible circular locking dependency detected ]
[ 219.553192] 3.12.4-01557-g9921cde-dirty #134 Not tainted
[ 219.558471] ---
[ 219.564727] rmmod/1517 is trying to acquire lock:
[ 219.569427] (s_active#35){.+}, at: [c017ab00]
sysfs_hash_and_remove+0x4c/0x8c
[ 219.577239]
[ 219.577239] but task is already holding lock:
[ 219.583068] (pwm_lock){+.+.+.}, at: [c0303598] pwmchip_remove+0x14/0xf8
[ 219.589996]
[ 219.589996] which lock already depends on the new lock.
[ 219.589996]
[ 219.598144]
[ 219.598144] the existing dependency chain (in reverse order) is:
[ 219.605590]
- #1 (pwm_lock){+.+.+.}:
[ 219.609497][c00a2d1c] lock_acquire+0x9c/0x128
[ 219.614746][c0639bc0] mutex_lock_nested+0x50/0x3dc
[ 219.620391][c0303974] pwm_request_from_chip+0x38/0x6c
[ 219.626312][c0303fe0] pwm_export_store+0x50/0x140
[ 219.631896][c039aba8] dev_attr_store+0x18/0x24
[ 219.637207][c017aff0] sysfs_write_file+0x16c/0x1a0
[ 219.642883][c0119084] vfs_write+0xb0/0x188
[ 219.647857][c0119478] SyS_write+0x3c/0x70
[ 219.652770][c0014100] ret_fast_syscall+0x0/0x48
[ 219.658172]
- #0 (s_active#35){.+}:
[ 219.662353][c00a2778] __lock_acquire+0x1b28/0x1b70
[ 219.667999][c00a2d1c] lock_acquire+0x9c/0x128
[ 219.673248][c017c780] sysfs_addrm_finish+0xe8/0x158
[ 219.678985][c017ab00] sysfs_hash_and_remove+0x4c/0x8c
[ 219.684906][c017e224] remove_files+0x38/0x74
[ 219.690063][c017e2a4] sysfs_remove_group+0x44/0x108
[ 219.695800][c017e38c] sysfs_remove_groups+0x24/0x34
[ 219.701538][c039bc2c] device_del+0xec/0x178
[ 219.706604][c039bcc4] device_unregister+0xc/0x18
[ 219.712097][c0303658] pwmchip_remove+0xd4/0xf8
[ 219.717407][c039fdc4] platform_drv_remove+0x18/0x1c
[ 219.723175][c039e6c4] __device_release_driver+0x70/0xc8
[ 219.729248][c039eec8] driver_detach+0xb4/0xb8
[ 219.734497][c039e4ec] bus_remove_driver+0x8c/0xd0
[ 219.740081][c00abd2c] SyS_delete_module+0x118/0x22c
[ 219.745819][c0014100] ret_fast_syscall+0x0/0x48
[ 219.751220]
[ 219.751220] other info that might help us debug this:
[ 219.751220]
[ 219.759216] Possible unsafe locking scenario:
[ 219.759216]
[ 219.765106]CPU0CPU1
[ 219.769622]
[ 219.774139] lock(pwm_lock);
[ 219.777130]lock(s_active#35);
[ 219.782897]lock(pwm_lock);
[ 219.788391] lock(s_active#35);
[ 219.791656]
[ 219.791656] *** DEADLOCK ***
[ 219.791656]
[ 219.797546] 3 locks held by rmmod/1517:
[ 219.801391] #0: (__lockdep_no_validate__){..}, at: [c039ee58]
driver_detach+0x44/0xb8
[ 219.810028] #1: (__lockdep_no_validate__){..}, at: [c039ee64]
driver_detach+0x50/0xb8
[ 219.818695] #2: (pwm_lock){+.+.+.}, at: [c0303598]
pwmchip_remove+0x14/0xf8
[ 219.826049]
[ 219.826049] stack backtrace:
[ 219.830413] CPU: 0 PID: 1517 Comm: rmmod Not tainted
3.12.4-01557-g9921cde-dirty #134
[ 219.838256] [c001cc98] (unwind_backtrace+0x0/0xf0) from [c0018124]
(show_stack+0x10/0x14)
[ 219.846771] [c0018124] (show_stack+0x10/0x14) from [c0636728]
(dump_stack+0x74/0xb4)
[ 219.854858] [c0636728] (dump_stack+0x74/0xb4) from [c06344e4]
(print_circular_bug+0x284/0x2d8)
[ 219.863830] [c06344e4] (print_circular_bug+0x284/0x2d8) from [c00a2778]
(__lock_acquire+0x1b28/0x1b70)
[ 219.873443] [c00a2778] (__lock_acquire+0x1b28/0x1b70) from [c00a2d1c]
(lock_acquire+0x9c/0x128)
[ 219.882476] [c00a2d1c] (lock_acquire+0x9c/0x128) from [c017c780]
(sysfs_addrm_finish+0xe8/0x158)
[ 219.891601] [c017c780] (sysfs_addrm_finish+0xe8/0x158) from [c017ab00]
(sysfs_hash_and_remove+0x4c/0x8c)
[ 219.901397] [c017ab00] (sysfs_hash_and_remove+0x4c/0x8c) from [c017e224]
(remove_files+0x38/0x74)
[ 219.910614] [c017e224] (remove_files+0x38/0x74) from [c017e2a4]
(sysfs_remove_group+0x44/0x108)
[ 219.919647] [c017e2a4] (sysfs_remove_group+0x44/0x108) from [c017e38c]
(sysfs_remove_groups+0x24/0x34)
[ 219.929260] [c017e38c] (sysfs_remove_groups+0x24/0x34) from [c039bc2c]
(device_del+0xec/0x178)
[ 219.938201] [c039bc2c] (device_del+0xec/0x178) from [c039bcc4]
(device_unregister+0xc/0x18)
[ 219.946899] [c039bcc4] (device_unregister+0xc/0x18) from [c0303658]
(pwmchip_remove+0xd4/0xf8)
[ 219.955841] [c0303658] (pwmchip_remove+0xd4/0xf8) from [c039fdc4]
(platform_drv_remove+0x18/0x1c)
[ 219.965057] [c039fdc4] (platform_drv_remove+0x18/0x1c) from [c039e6c4]
(__device_release_driver+0x70/0xc8)
[ 219.975006] [c039e6c4] (__device_release_driver+0x70/0xc8) from
