Commit 8a6543ba authored by Ville Syrjälä's avatar Ville Syrjälä Committed by Daniel Vetter

drm/i915: Fix deadlock during driver init on ILK

We have a struct_mutex deadlock during driver init on ILK

[   54.320273] =============================================
[   54.320371] [ INFO: possible recursive locking detected ]
[   54.320471] 3.15.0-rc2-flip_race+ #2 Not tainted
[   54.320567] ---------------------------------------------
[   54.320665] modprobe/2178 is trying to acquire lock:
[   54.320762]  (&dev->struct_mutex){+.+.+.}, at: [<ffffffffa0568b05>] intel_enable_gt_powersave+0xa5/0x9d0 [i915]
[   54.321111]
[   54.321111] but task is already holding lock:
[   54.321250]  (&dev->struct_mutex){+.+.+.}, at: [<ffffffffa05b4c2e>] intel_modeset_init_hw+0x3e/0x60 [i915]
[   54.321583]
[   54.321583] other info that might help us debug this:
[   54.321724]  Possible unsafe locking scenario:
[   54.321724]
[   54.321863]        CPU0
[   54.321954]        ----
[   54.322046]   lock(&dev->struct_mutex);
[   54.322221]   lock(&dev->struct_mutex);
[   54.322397]
[   54.322397]  *** DEADLOCK ***
[   54.322397]
[   54.322638]  May be due to missing lock nesting notation
[   54.322638]
[   54.322781] 4 locks held by modprobe/2178:
[   54.322875]  #0:  (&dev->mutex){......}, at: [<ffffffff813592eb>] __driver_attach+0x5b/0xb0
[   54.323230]  #1:  (&dev->mutex){......}, at: [<ffffffff813592f9>] __driver_attach+0x69/0xb0
[   54.323582]  #2:  (drm_global_mutex){+.+.+.}, at: [<ffffffffa04e1e0d>] drm_dev_register+0x2d/0x120 [drm]
[   54.323945]  #3:  (&dev->struct_mutex){+.+.+.}, at: [<ffffffffa05b4c2e>] intel_modeset_init_hw+0x3e/0x60 [i915]

This regression got introduced in:
 commit 586d5270b60dc1f35cc3ca982d403765bad77965
 Author: Imre Deak <imre.deak@intel.com>
 Date:   Mon Apr 14 20:24:28 2014 +0300

    drm/i915: move getting struct_mutex lower in the callstack during GPU reset

Fix the problem by not taking struct_mutex around intel_enable_gt_powersave()
in intel_modeset_init_hw() since intel_enable_gt_powersave() now grabs the
mutex itself.
Signed-off-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent 713028b3
...@@ -11252,9 +11252,7 @@ void intel_modeset_init_hw(struct drm_device *dev) ...@@ -11252,9 +11252,7 @@ void intel_modeset_init_hw(struct drm_device *dev)
intel_reset_dpio(dev); intel_reset_dpio(dev);
mutex_lock(&dev->struct_mutex);
intel_enable_gt_powersave(dev); intel_enable_gt_powersave(dev);
mutex_unlock(&dev->struct_mutex);
} }
void intel_modeset_suspend_hw(struct drm_device *dev) void intel_modeset_suspend_hw(struct drm_device *dev)
......
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