diff options
author | Jani Nikula <jani.nikula@intel.com> | 2021-10-01 12:14:44 +0300 |
---|---|---|
committer | Jani Nikula <jani.nikula@intel.com> | 2021-10-13 15:54:46 +0300 |
commit | cd06ab2fd48f2c0243b06344a36056e811d263b8 (patch) | |
tree | 2a45e8267cf5785794eebf6c39ce2043bfb9b8f5 /include/drm/drm_modeset_lock.h | |
parent | 91302d6c1dfd438b53237831f1f78dfbfd8ce934 (diff) | |
download | linux-stable-cd06ab2fd48f2c0243b06344a36056e811d263b8.tar.gz linux-stable-cd06ab2fd48f2c0243b06344a36056e811d263b8.tar.bz2 linux-stable-cd06ab2fd48f2c0243b06344a36056e811d263b8.zip |
drm/locking: add backtrace for locking contended locks without backoff
If drm_modeset_lock() returns -EDEADLK, the caller is supposed to drop
all currently held locks using drm_modeset_backoff(). Failing to do so
will result in warnings and backtraces on the paths trying to lock a
contended lock. Add support for optionally printing the backtrace on the
path that hit the deadlock and didn't gracefully handle the situation.
For example, the patch [1] inadvertently dropped the return value check
and error return on replacing calc_watermark_data() with
intel_compute_global_watermarks(). The backtraces on the subsequent
locking paths hitting WARN_ON(ctx->contended) were unhelpful, but adding
the backtrace to the deadlock path produced this helpful printout:
<7> [98.002465] drm_modeset_lock attempting to lock a contended lock without backoff:
drm_modeset_lock+0x107/0x130
drm_atomic_get_plane_state+0x76/0x150
skl_compute_wm+0x251d/0x2b20 [i915]
intel_atomic_check+0x1942/0x29e0 [i915]
drm_atomic_check_only+0x554/0x910
drm_atomic_nonblocking_commit+0xe/0x50
drm_mode_atomic_ioctl+0x8c2/0xab0
drm_ioctl_kernel+0xac/0x140
Add new CONFIG_DRM_DEBUG_MODESET_LOCK to enable modeset lock debugging
with stack depot and trace.
[1] https://lore.kernel.org/r/20210924114741.15940-4-jani.nikula@intel.com
v2:
- default y if DEBUG_WW_MUTEX_SLOWPATH (Daniel)
- depends on DEBUG_KERNEL
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Dave Airlie <airlied@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211001091444.8177-1-jani.nikula@intel.com
Diffstat (limited to 'include/drm/drm_modeset_lock.h')
-rw-r--r-- | include/drm/drm_modeset_lock.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/drm/drm_modeset_lock.h b/include/drm/drm_modeset_lock.h index aafd07388eb7..b84693fbd2b5 100644 --- a/include/drm/drm_modeset_lock.h +++ b/include/drm/drm_modeset_lock.h @@ -24,6 +24,8 @@ #ifndef DRM_MODESET_LOCK_H_ #define DRM_MODESET_LOCK_H_ +#include <linux/types.h> /* stackdepot.h is not self-contained */ +#include <linux/stackdepot.h> #include <linux/ww_mutex.h> struct drm_modeset_lock; @@ -52,6 +54,12 @@ struct drm_modeset_acquire_ctx { struct drm_modeset_lock *contended; /* + * Stack depot for debugging when a contended lock was not backed off + * from. + */ + depot_stack_handle_t stack_depot; + + /* * list of held locks (drm_modeset_lock) */ struct list_head locked; |