[PATCH] drm: serialize access to debugs_nodes.list

[PATCH] drm: serialize access to debugs_nodes.list

[Marcin Slusarz]

Nouveau, when configured with debugfs, creates debugfs files for every
channel, so structure holding list of files needs to be protected from
simultaneous changes by multiple threads.

Without this patch it's possible to hit kernel oops in
drm_debugfs_remove_files just by running a couple of xterms with
looped glxinfo.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
---
 drivers/gpu/drm/drm_debugfs.c |    5 +++++
 include/drm/drmP.h            |    1 +
 2 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
index 9d2668a..1144fbe 100644
--- a/drivers/gpu/drm/drm_debugfs.c
+++ b/drivers/gpu/drm/drm_debugfs.c
@@ -120,7 +120,9 @@ int drm_debugfs_create_files(struct drm_info_list *files, int count,
 		tmp->minor = minor;
 		tmp->dent = ent;
 		tmp->info_ent = &files[i];
+		mutex_lock(&minor->debugfs_nodes.mutex);
 		list_add(&(tmp->list), &(minor->debugfs_nodes.list));
+		mutex_unlock(&minor->debugfs_nodes.mutex);
 	}
 	return 0;
 
@@ -149,6 +151,7 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
 	int ret;
 
 	INIT_LIST_HEAD(&minor->debugfs_nodes.list);
+	mutex_init(&minor->debugfs_nodes.mutex);
 	sprintf(name, "%d", minor_id);
 	minor->debugfs_root = debugfs_create_dir(name, root);
 	if (!minor->debugfs_root) {
@@ -194,6 +197,7 @@ int drm_debugfs_remove_files(struct drm_info_list *files, int count,
 	struct drm_info_node *tmp;
 	int i;
 
+	mutex_lock(&minor->debugfs_nodes.mutex);
 	for (i = 0; i < count; i++) {
 		list_for_each_safe(pos, q, &minor->debugfs_nodes.list) {
 			tmp = list_entry(pos, struct drm_info_node, list);
@@ -204,6 +208,7 @@ int drm_debugfs_remove_files(struct drm_info_list *files, int count,
 			}
 		}
 	}
+	mutex_unlock(&minor->debugfs_nodes.mutex);
 	return 0;
 }
 EXPORT_SYMBOL(drm_debugfs_remove_files);
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 9b7c2bb..c70c943 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -970,6 +970,7 @@ struct drm_info_list {
  * debugfs node structure. This structure represents a debugfs file.
  */
 struct drm_info_node {
+	struct mutex mutex;
 	struct list_head list;
 	struct drm_minor *minor;
 	struct drm_info_list *info_ent;
-- 
1.7.7

Re: [PATCH] drm: serialize access to debugs_nodes.list

[Daniel Vetter]

On Sun, Oct 30, 2011 at 11:04:48PM +0100, Marcin Slusarz wrote:
> Nouveau, when configured with debugfs, creates debugfs files for every
> channel, so structure holding list of files needs to be protected from
> simultaneous changes by multiple threads.
> 
> Without this patch it's possible to hit kernel oops in
> drm_debugfs_remove_files just by running a couple of xterms with
> looped glxinfo.
> 
> Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
> ---
>  drivers/gpu/drm/drm_debugfs.c |    5 +++++
>  include/drm/drmP.h            |    1 +
>  2 files changed, 6 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
> index 9d2668a..1144fbe 100644
> --- a/drivers/gpu/drm/drm_debugfs.c
> +++ b/drivers/gpu/drm/drm_debugfs.c
> @@ -120,7 +120,9 @@ int drm_debugfs_create_files(struct drm_info_list *files, int count,
>  		tmp->minor = minor;
>  		tmp->dent = ent;
>  		tmp->info_ent = &files[i];
> +		mutex_lock(&minor->debugfs_nodes.mutex);
>  		list_add(&(tmp->list), &(minor->debugfs_nodes.list));
> +		mutex_unlock(&minor->debugfs_nodes.mutex);
>  	}
>  	return 0;
>  
> @@ -149,6 +151,7 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
>  	int ret;
>  
>  	INIT_LIST_HEAD(&minor->debugfs_nodes.list);
> +	mutex_init(&minor->debugfs_nodes.mutex);
>  	sprintf(name, "%d", minor_id);
>  	minor->debugfs_root = debugfs_create_dir(name, root);
>  	if (!minor->debugfs_root) {
> @@ -194,6 +197,7 @@ int drm_debugfs_remove_files(struct drm_info_list *files, int count,
>  	struct drm_info_node *tmp;
>  	int i;
>  
> +	mutex_lock(&minor->debugfs_nodes.mutex);
>  	for (i = 0; i < count; i++) {
>  		list_for_each_safe(pos, q, &minor->debugfs_nodes.list) {
>  			tmp = list_entry(pos, struct drm_info_node, list);
> @@ -204,6 +208,7 @@ int drm_debugfs_remove_files(struct drm_info_list *files, int count,
>  			}
>  		}
>  	}
> +	mutex_unlock(&minor->debugfs_nodes.mutex);
>  	return 0;
>  }
>  EXPORT_SYMBOL(drm_debugfs_remove_files);
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index 9b7c2bb..c70c943 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -970,6 +970,7 @@ struct drm_info_list {
>   * debugfs node structure. This structure represents a debugfs file.
>   */
>  struct drm_info_node {
> +	struct mutex mutex;
>  	struct list_head list;
>  	struct drm_minor *minor;
>  	struct drm_info_list *info_ent;

This is just ugly, you're adding a mutex to every drm_info_node, but only
use the one embedded into the minor. On a quick grep we're only ever using
the list in there, so I suggest to
- replace minor->debugfs_node.list with minor->debugfs_list and kill
  ->debugfs_node
- add the mutex as minor->debugfs_lock
That way it's clear what's going on.

Also, you've forgotten to add the locking to i915/i915_debugfs.c

Yours, Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48

Re: [PATCH] drm: serialize access to debugs_nodes.list

[Marcin Slusarz]

On Mon, Oct 31, 2011 at 09:06:57AM +0100, Daniel Vetter wrote:
> This is just ugly, you're adding a mutex to every drm_info_node, but only
> use the one embedded into the minor. On a quick grep we're only ever using
> the list in there, so I suggest to
> - replace minor->debugfs_node.list with minor->debugfs_list and kill
>   ->debugfs_node
> - add the mutex as minor->debugfs_lock
> That way it's clear what's going on.

Yes, you are right. I don't know what the heck I was thinking.

> Also, you've forgotten to add the locking to i915/i915_debugfs.c

Yeah. Will fix it too.

Marcin

[PATCH] drm: serialize access to list of debugfs files

[Marcin Slusarz]

Nouveau, when configured with debugfs, creates debugfs files for every
channel, so structure holding list of files needs to be protected from
simultaneous changes by multiple threads.

Without this patch it's possible to hit kernel oops in
drm_debugfs_remove_files just by running a couple of xterms with
looped glxinfo.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
---
 drivers/gpu/drm/drm_debugfs.c       |   12 +++++++++---
 drivers/gpu/drm/i915/i915_debugfs.c |    5 ++++-
 include/drm/drmP.h                  |    4 +++-
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
index 9d2668a..d34d4fc 100644
--- a/drivers/gpu/drm/drm_debugfs.c
+++ b/drivers/gpu/drm/drm_debugfs.c
@@ -120,7 +120,10 @@ int drm_debugfs_create_files(struct drm_info_list *files, int count,
 		tmp->minor = minor;
 		tmp->dent = ent;
 		tmp->info_ent = &files[i];
-		list_add(&(tmp->list), &(minor->debugfs_nodes.list));
+
+		mutex_lock(&minor->debugfs_lock);
+		list_add(&tmp->list, &minor->debugfs_list);
+		mutex_unlock(&minor->debugfs_lock);
 	}
 	return 0;
 
@@ -148,7 +151,8 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
 	char name[64];
 	int ret;
 
-	INIT_LIST_HEAD(&minor->debugfs_nodes.list);
+	INIT_LIST_HEAD(&minor->debugfs_list);
+	mutex_init(&minor->debugfs_lock);
 	sprintf(name, "%d", minor_id);
 	minor->debugfs_root = debugfs_create_dir(name, root);
 	if (!minor->debugfs_root) {
@@ -194,8 +198,9 @@ int drm_debugfs_remove_files(struct drm_info_list *files, int count,
 	struct drm_info_node *tmp;
 	int i;
 
+	mutex_lock(&minor->debugfs_lock);
 	for (i = 0; i < count; i++) {
-		list_for_each_safe(pos, q, &minor->debugfs_nodes.list) {
+		list_for_each_safe(pos, q, &minor->debugfs_list) {
 			tmp = list_entry(pos, struct drm_info_node, list);
 			if (tmp->info_ent == &files[i]) {
 				debugfs_remove(tmp->dent);
@@ -204,6 +209,7 @@ int drm_debugfs_remove_files(struct drm_info_list *files, int count,
 			}
 		}
 	}
+	mutex_unlock(&minor->debugfs_lock);
 	return 0;
 }
 EXPORT_SYMBOL(drm_debugfs_remove_files);
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 3c395a5..fdad293 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1505,7 +1505,10 @@ drm_add_fake_info_node(struct drm_minor *minor,
 	node->minor = minor;
 	node->dent = ent;
 	node->info_ent = (void *) key;
-	list_add(&node->list, &minor->debugfs_nodes.list);
+
+	mutex_lock(&minor->debugfs_lock);
+	list_add(&node->list, &minor->debugfs_list);
+	mutex_unlock(&minor->debugfs_lock);
 
 	return 0;
 }
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 9b7c2bb..40e9ea3 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -989,7 +989,9 @@ struct drm_minor {
 	struct proc_dir_entry *proc_root;  /**< proc directory entry */
 	struct drm_info_node proc_nodes;
 	struct dentry *debugfs_root;
-	struct drm_info_node debugfs_nodes;
+
+	struct list_head debugfs_list;
+	struct mutex debugfs_lock; /* Protects debugfs_list. */
 
 	struct drm_master *master; /* currently active master for this node */
 	struct list_head master_list;
-- 
1.7.7

Re: [PATCH] drm: serialize access to list of debugfs files

[Daniel Vetter]

On Mon, Oct 31, 2011 at 06:33:57PM +0100, Marcin Slusarz wrote:
> Nouveau, when configured with debugfs, creates debugfs files for every
> channel, so structure holding list of files needs to be protected from
> simultaneous changes by multiple threads.
> 
> Without this patch it's possible to hit kernel oops in
> drm_debugfs_remove_files just by running a couple of xterms with
> looped glxinfo.
> 
> Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>

And v2 also includes a nice comment in the header explaining the locking.
Awesome!
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48

[PATCH] drm: serialize access to list of debugfs files

[Marcin Slusarz]

Nouveau, when configured with debugfs, creates debugfs files for every
channel, so structure holding list of files needs to be protected from
simultaneous changes by multiple threads.

Without this patch it's possible to hit kernel oops in
drm_debugfs_remove_files just by running a couple of xterms with
looped glxinfo.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
Updated changelog.
---
 drivers/gpu/drm/drm_debugfs.c       |   12 +++++++++---
 drivers/gpu/drm/i915/i915_debugfs.c |    5 ++++-
 include/drm/drmP.h                  |    4 +++-
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
index d067c12..1c7a1c0 100644
--- a/drivers/gpu/drm/drm_debugfs.c
+++ b/drivers/gpu/drm/drm_debugfs.c
@@ -118,7 +118,10 @@ int drm_debugfs_create_files(struct drm_info_list *files, int count,
 		tmp->minor = minor;
 		tmp->dent = ent;
 		tmp->info_ent = &files[i];
-		list_add(&(tmp->list), &(minor->debugfs_nodes.list));
+
+		mutex_lock(&minor->debugfs_lock);
+		list_add(&tmp->list, &minor->debugfs_list);
+		mutex_unlock(&minor->debugfs_lock);
 	}
 	return 0;
 
@@ -146,7 +149,8 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
 	char name[64];
 	int ret;
 
-	INIT_LIST_HEAD(&minor->debugfs_nodes.list);
+	INIT_LIST_HEAD(&minor->debugfs_list);
+	mutex_init(&minor->debugfs_lock);
 	sprintf(name, "%d", minor_id);
 	minor->debugfs_root = debugfs_create_dir(name, root);
 	if (!minor->debugfs_root) {
@@ -192,8 +196,9 @@ int drm_debugfs_remove_files(struct drm_info_list *files, int count,
 	struct drm_info_node *tmp;
 	int i;
 
+	mutex_lock(&minor->debugfs_lock);
 	for (i = 0; i < count; i++) {
-		list_for_each_safe(pos, q, &minor->debugfs_nodes.list) {
+		list_for_each_safe(pos, q, &minor->debugfs_list) {
 			tmp = list_entry(pos, struct drm_info_node, list);
 			if (tmp->info_ent == &files[i]) {
 				debugfs_remove(tmp->dent);
@@ -202,6 +207,7 @@ int drm_debugfs_remove_files(struct drm_info_list *files, int count,
 			}
 		}
 	}
+	mutex_unlock(&minor->debugfs_lock);
 	return 0;
 }
 EXPORT_SYMBOL(drm_debugfs_remove_files);
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index d14b44e..4f40f1c 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1506,7 +1506,10 @@ drm_add_fake_info_node(struct drm_minor *minor,
 	node->minor = minor;
 	node->dent = ent;
 	node->info_ent = (void *) key;
-	list_add(&node->list, &minor->debugfs_nodes.list);
+
+	mutex_lock(&minor->debugfs_lock);
+	list_add(&node->list, &minor->debugfs_list);
+	mutex_unlock(&minor->debugfs_lock);
 
 	return 0;
 }
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index cf39949..1f9e951 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -990,7 +990,9 @@ struct drm_minor {
 	struct proc_dir_entry *proc_root;  /**< proc directory entry */
 	struct drm_info_node proc_nodes;
 	struct dentry *debugfs_root;
-	struct drm_info_node debugfs_nodes;
+
+	struct list_head debugfs_list;
+	struct mutex debugfs_lock; /* Protects debugfs_list. */
 
 	struct drm_master *master; /* currently active master for this node */
 	struct list_head master_list;
-- 
1.7.7.2