| Message ID | 1387366615-23182-2-git-send-email-sourav.poddar@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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] CPU0 CPU1 > [ 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 [<c039eec8>] (driver_detach+0xb4/0xb8) > [ 219.984466] [<c039eec8>] (driver_detach+0xb4/0xb8) from [<c039e4ec>] (bus_remove_driver+0x8c/0xd0) > [ 219.993438] [<c039e4ec>] (bus_remove_driver+0x8c/0xd0) from [<c00abd2c>] (SyS_delete_module+0x118/0x22c) > [ 220.002899] [<c00abd2c>] (SyS_delete_module+0x118/0x22c) from [<c0014100>] (ret_fast_syscall+0x0/0x48) > > Looks like s_active lock cannot be held while pwm lock is held. > The patch fixes the above issue by unlocking the pwm lock before acquiring the > sysfs lock. I've been trying to reproduce this, but I can't. I've enabled LOCKDEP and PROVE_LOCKING in Kconfig, booted a Tegra-based board and did a couple of modprobe pwm-tegra && modprobe -r pwm-tegra. But I never saw LOCKDEP complain. Can you reproduce the issue on latest linux-next? Or is there something else I should be doing to trigger this? Thierry
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index 2ca9504..3e1d499 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -300,6 +300,7 @@ int pwmchip_remove(struct pwm_chip *chip) if (test_bit(PWMF_REQUESTED, &pwm->flags)) { ret = -EBUSY; + mutex_unlock(&pwm_lock); goto out; } } @@ -311,10 +312,11 @@ int pwmchip_remove(struct pwm_chip *chip) free_pwms(chip); + mutex_unlock(&pwm_lock); + pwmchip_sysfs_unexport(chip); out: - mutex_unlock(&pwm_lock); return ret; } EXPORT_SYMBOL_GPL(pwmchip_remove);
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] CPU0 CPU1 [ 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 [<c039eec8>] (driver_detach+0xb4/0xb8) [ 219.984466] [<c039eec8>] (driver_detach+0xb4/0xb8) from [<c039e4ec>] (bus_remove_driver+0x8c/0xd0) [ 219.993438] [<c039e4ec>] (bus_remove_driver+0x8c/0xd0) from [<c00abd2c>] (SyS_delete_module+0x118/0x22c) [ 220.002899] [<c00abd2c>] (SyS_delete_module+0x118/0x22c) from [<c0014100>] (ret_fast_syscall+0x0/0x48) Looks like s_active lock cannot be held while pwm lock is held. The patch fixes the above issue by unlocking the pwm lock before acquiring the sysfs lock. Signed-off-by: Sourav Poddar <sourav.poddar@ti.com> --- drivers/pwm/core.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-)