From 8a6543ba4719ff940b22ce9f9830a9c3fd9e1b60 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Fri, 25 Apr 2014 22:11:51 +0300 Subject: [PATCH] drm/i915: Fix deadlock during driver init on ILK MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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: [] intel_enable_gt_powersave+0xa5/0x9d0 [i915] [ 54.321111] [ 54.321111] but task is already holding lock: [ 54.321250] (&dev->struct_mutex){+.+.+.}, at: [] 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: [] __driver_attach+0x5b/0xb0 [ 54.323230] #1: (&dev->mutex){......}, at: [] __driver_attach+0x69/0xb0 [ 54.323582] #2: (drm_global_mutex){+.+.+.}, at: [] drm_dev_register+0x2d/0x120 [drm] [ 54.323945] #3: (&dev->struct_mutex){+.+.+.}, at: [] intel_modeset_init_hw+0x3e/0x60 [i915] This regression got introduced in: commit 586d5270b60dc1f35cc3ca982d403765bad77965 Author: Imre Deak 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: Ville Syrjälä Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/intel_display.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 4717ddbbfe2d..423f44ba2b43 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -11252,9 +11252,7 @@ void intel_modeset_init_hw(struct drm_device *dev) intel_reset_dpio(dev); - mutex_lock(&dev->struct_mutex); intel_enable_gt_powersave(dev); - mutex_unlock(&dev->struct_mutex); } void intel_modeset_suspend_hw(struct drm_device *dev) -- 2.11.0