Re: [PATCH 08/35] drm: Protect dev->filelist with its own mutex

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Apr 26, 2016 at 07:29:41PM +0200, Daniel Vetter wrote:
> amdgpu gained dev->struct_mutex usage, and that's because it's walking
> the dev->filelist list. Protect that list with it's own lock to take
> one more step towards getting rid of struct_mutex usage in drivers
> once and for all.
> 
> While doing the conversion I noticed that 2 debugfs files in i915
> completely lacked appropriate locking. Fix that up too.
> 
> v2: don't forget to switch to drm_gem_object_unreference_unlocked.
> 
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

Ok, merged up to this patch to drm-misc, thanks a lot for feedback and
review.
-Daniel

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 10 +++++-----
>  drivers/gpu/drm/drm_drv.c               |  1 +
>  drivers/gpu/drm/drm_fops.c              |  9 ++++++---
>  drivers/gpu/drm/drm_info.c              |  4 ++--
>  drivers/gpu/drm/i915/i915_debugfs.c     | 12 ++++++++++--
>  include/drm/drmP.h                      |  1 +
>  6 files changed, 25 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index fa6a27bff298..a087b9638cde 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -93,7 +93,7 @@ void amdgpu_gem_force_release(struct amdgpu_device *adev)
>  	struct drm_device *ddev = adev->ddev;
>  	struct drm_file *file;
>  
> -	mutex_lock(&ddev->struct_mutex);
> +	mutex_lock(&ddev->filelist_mutex);
>  
>  	list_for_each_entry(file, &ddev->filelist, lhead) {
>  		struct drm_gem_object *gobj;
> @@ -103,13 +103,13 @@ void amdgpu_gem_force_release(struct amdgpu_device *adev)
>  		spin_lock(&file->table_lock);
>  		idr_for_each_entry(&file->object_idr, gobj, handle) {
>  			WARN_ONCE(1, "And also active allocations!\n");
> -			drm_gem_object_unreference(gobj);
> +			drm_gem_object_unreference_unlocked(gobj);
>  		}
>  		idr_destroy(&file->object_idr);
>  		spin_unlock(&file->table_lock);
>  	}
>  
> -	mutex_unlock(&ddev->struct_mutex);
> +	mutex_unlock(&ddev->filelist_mutex);
>  }
>  
>  /*
> @@ -769,7 +769,7 @@ static int amdgpu_debugfs_gem_info(struct seq_file *m, void *data)
>  	struct drm_file *file;
>  	int r;
>  
> -	r = mutex_lock_interruptible(&dev->struct_mutex);
> +	r = mutex_lock_interruptible(&dev->filelist_mutex);
>  	if (r)
>  		return r;
>  
> @@ -793,7 +793,7 @@ static int amdgpu_debugfs_gem_info(struct seq_file *m, void *data)
>  		spin_unlock(&file->table_lock);
>  	}
>  
> -	mutex_unlock(&dev->struct_mutex);
> +	mutex_unlock(&dev->filelist_mutex);
>  	return 0;
>  }
>  
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index e1fb52d4f72c..bff89226a344 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -590,6 +590,7 @@ struct drm_device *drm_dev_alloc(struct drm_driver *driver,
>  	spin_lock_init(&dev->buf_lock);
>  	spin_lock_init(&dev->event_lock);
>  	mutex_init(&dev->struct_mutex);
> +	mutex_init(&dev->filelist_mutex);
>  	mutex_init(&dev->ctxlist_mutex);
>  	mutex_init(&dev->master_mutex);
>  
> diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
> index c3d0aaac0669..7af7f8bcb355 100644
> --- a/drivers/gpu/drm/drm_fops.c
> +++ b/drivers/gpu/drm/drm_fops.c
> @@ -297,9 +297,9 @@ static int drm_open_helper(struct file *filp, struct drm_minor *minor)
>  	}
>  	mutex_unlock(&dev->master_mutex);
>  
> -	mutex_lock(&dev->struct_mutex);
> +	mutex_lock(&dev->filelist_mutex);
>  	list_add(&priv->lhead, &dev->filelist);
> -	mutex_unlock(&dev->struct_mutex);
> +	mutex_unlock(&dev->filelist_mutex);
>  
>  #ifdef __alpha__
>  	/*
> @@ -447,8 +447,11 @@ int drm_release(struct inode *inode, struct file *filp)
>  
>  	DRM_DEBUG("open_count = %d\n", dev->open_count);
>  
> -	mutex_lock(&dev->struct_mutex);
> +	mutex_lock(&dev->filelist_mutex);
>  	list_del(&file_priv->lhead);
> +	mutex_unlock(&dev->filelist_mutex);
> +
> +	mutex_lock(&dev->struct_mutex);
>  	if (file_priv->magic)
>  		idr_remove(&file_priv->master->magic_map, file_priv->magic);
>  	mutex_unlock(&dev->struct_mutex);
> diff --git a/drivers/gpu/drm/drm_info.c b/drivers/gpu/drm/drm_info.c
> index cbb4fc0fc969..5d469b2f26f4 100644
> --- a/drivers/gpu/drm/drm_info.c
> +++ b/drivers/gpu/drm/drm_info.c
> @@ -174,7 +174,7 @@ int drm_clients_info(struct seq_file *m, void *data)
>  	/* dev->filelist is sorted youngest first, but we want to present
>  	 * oldest first (i.e. kernel, servers, clients), so walk backwardss.
>  	 */
> -	mutex_lock(&dev->struct_mutex);
> +	mutex_lock(&dev->filelist_mutex);
>  	list_for_each_entry_reverse(priv, &dev->filelist, lhead) {
>  		struct task_struct *task;
>  
> @@ -190,7 +190,7 @@ int drm_clients_info(struct seq_file *m, void *data)
>  			   priv->magic);
>  		rcu_read_unlock();
>  	}
> -	mutex_unlock(&dev->struct_mutex);
> +	mutex_unlock(&dev->filelist_mutex);
>  	return 0;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index 4950d05d2948..8b8d6f07d7aa 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -528,6 +528,10 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
>  
>  	seq_putc(m, '\n');
>  	print_batch_pool_stats(m, dev_priv);
> +
> +	mutex_unlock(&dev->struct_mutex);
> +
> +	mutex_lock(&dev->filelist_mutex);
>  	list_for_each_entry_reverse(file, &dev->filelist, lhead) {
>  		struct file_stats stats;
>  		struct task_struct *task;
> @@ -548,8 +552,7 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
>  		print_file_stats(m, task ? task->comm : "<unknown>", stats);
>  		rcu_read_unlock();
>  	}
> -
> -	mutex_unlock(&dev->struct_mutex);
> +	mutex_unlock(&dev->filelist_mutex);
>  
>  	return 0;
>  }
> @@ -2354,6 +2357,7 @@ static int i915_ppgtt_info(struct seq_file *m, void *data)
>  	else if (INTEL_INFO(dev)->gen >= 6)
>  		gen6_ppgtt_info(m, dev);
>  
> +	mutex_lock(&dev->filelist_mutex);
>  	list_for_each_entry_reverse(file, &dev->filelist, lhead) {
>  		struct drm_i915_file_private *file_priv = file->driver_priv;
>  		struct task_struct *task;
> @@ -2368,6 +2372,7 @@ static int i915_ppgtt_info(struct seq_file *m, void *data)
>  		idr_for_each(&file_priv->context_idr, per_file_ctx,
>  			     (void *)(unsigned long)m);
>  	}
> +	mutex_unlock(&dev->filelist_mutex);
>  
>  out_put:
>  	intel_runtime_pm_put(dev_priv);
> @@ -2403,6 +2408,8 @@ static int i915_rps_boost_info(struct seq_file *m, void *data)
>  		   intel_gpu_freq(dev_priv, dev_priv->rps.min_freq_softlimit),
>  		   intel_gpu_freq(dev_priv, dev_priv->rps.max_freq_softlimit),
>  		   intel_gpu_freq(dev_priv, dev_priv->rps.max_freq));
> +
> +	mutex_lock(&dev->filelist_mutex);
>  	spin_lock(&dev_priv->rps.client_lock);
>  	list_for_each_entry_reverse(file, &dev->filelist, lhead) {
>  		struct drm_i915_file_private *file_priv = file->driver_priv;
> @@ -2425,6 +2432,7 @@ static int i915_rps_boost_info(struct seq_file *m, void *data)
>  		   list_empty(&dev_priv->rps.mmioflips.link) ? "" : ", active");
>  	seq_printf(m, "Kernel boosts: %d\n", dev_priv->rps.boosts);
>  	spin_unlock(&dev_priv->rps.client_lock);
> +	mutex_unlock(&dev->filelist_mutex);
>  
>  	return 0;
>  }
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index f82979dee647..c81dd2250fc6 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -769,6 +769,7 @@ struct drm_device {
>  	atomic_t buf_alloc;		/**< Buffer allocation in progress */
>  	/*@} */
>  
> +	struct mutex filelist_mutex;
>  	struct list_head filelist;
>  
>  	/** \name Memory management */
> -- 
> 2.8.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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