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 /drivers/gpu/drm/Kconfig | |
| parent | 91302d6c1dfd438b53237831f1f78dfbfd8ce934 (diff) | |
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 'drivers/gpu/drm/Kconfig')
| -rw-r--r-- | drivers/gpu/drm/Kconfig | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig index 2a926d0de423..a4c020a9a0eb 100644 --- a/drivers/gpu/drm/Kconfig +++ b/drivers/gpu/drm/Kconfig @@ -100,6 +100,21 @@ config DRM_DEBUG_DP_MST_TOPOLOGY_REFS This has the potential to use a lot of memory and print some very large kernel messages. If in doubt, say "N". +config DRM_DEBUG_MODESET_LOCK + bool "Enable backtrace history for lock contention" + depends on STACKTRACE_SUPPORT + depends on DEBUG_KERNEL + depends on EXPERT + select STACKDEPOT + default y if DEBUG_WW_MUTEX_SLOWPATH + help + Enable debug tracing of failures to gracefully handle drm modeset lock + contention. A history of each drm modeset lock path hitting -EDEADLK + will be saved until gracefully handled, and the backtrace will be + printed when attempting to lock a contended lock. + + If in doubt, say "N". + config DRM_FBDEV_EMULATION bool "Enable legacy fbdev support for your modesetting driver" depends on DRM |