[PATCH v3 13/23] drm/msm: Add priv->mm_lock to protect active/inactive lists

Rob Clark
2020-10-19T20:46:52Z

Rather than relying on the big dev->struct_mutex hammer, introduce a
more specific lock for protecting the bo lists.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Jordan Crouse <jcrouse@codeaurora.org>
---
drivers/gpu/drm/msm/msm_debugfs.c | 7 +++++++
drivers/gpu/drm/msm/msm_drv.c | 7 +++++++
drivers/gpu/drm/msm/msm_drv.h | 13 +++++++++++-
drivers/gpu/drm/msm/msm_gem.c | 28 +++++++++++++++-----------
drivers/gpu/drm/msm/msm_gem_shrinker.c | 12 +++++++++++
drivers/gpu/drm/msm/msm_gpu.h | 5 ++++-
6 files changed, 58 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_debugfs.c b/drivers/gpu/drm/msm/msm_debugfs.c
index ee2e270f464c..64afbed89821 100644
--- a/drivers/gpu/drm/msm/msm_debugfs.c
+++ b/drivers/gpu/drm/msm/msm_debugfs.c
@@ -112,6 +112,11 @@ static int msm_gem_show(struct drm_device *dev, struct seq_file *m)
{
struct msm_drm_private *priv = dev->dev_private;
struct msm_gpu *gpu = priv->gpu;
+ int ret;
+
+ ret = mutex_lock_interruptible(&priv->mm_lock);
+ if (ret)
+ return ret;

if (gpu) {
seq_printf(m, "Active Objects (%s):\n", gpu->name);
@@ -121,6 +126,8 @@ static int msm_gem_show(struct drm_device *dev, struct seq_file *m)
seq_printf(m, "Inactive Objects:\n");
msm_gem_describe_objects(&priv->inactive_list, m);

+ mutex_unlock(&priv->mm_lock);
+
return 0;
}

diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index 70bc4bb69edc..15c41786d018 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -7,6 +7,7 @@

#include <linux/dma-mapping.h>
#include <linux/kthread.h>
+#include <linux/sched/mm.h>
#include <linux/uaccess.h>
#include <uapi/linux/sched/types.h>

@@ -468,6 +469,12 @@ static int msm_drm_init(struct device *dev, struct drm_driver *drv)
init_llist_head(&priv->free_list);

INIT_LIST_HEAD(&priv->inactive_list);
+ mutex_init(&priv->mm_lock);
+
+ /* Teach lockdep about lock ordering wrt. shrinker: */
+ fs_reclaim_acquire(GFP_KERNEL);
+ might_lock(&priv->mm_lock);
+ fs_reclaim_release(GFP_KERNEL);

drm_mode_config_init(ddev);

diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index 713a0ae28125..7431d68ea102 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -174,8 +174,19 @@ struct msm_drm_private {
struct msm_rd_state *hangrd; /* debugfs to dump hanging submits */
struct msm_perf_state *perf;

- /* list of GEM objects: */
+ /*
+ * List of inactive GEM objects. Every bo is either in the inactive_list
+ * or gpu->active_list (for the gpu it is active on[1])
+ *
+ * These lists are protected by mm_lock. If struct_mutex is involved, it
+ * should be aquired prior to mm_lock. One should *not* hold mm_lock in
+ * get_pages()/vmap()/etc paths, as they can trigger the shrinker.
+ *
+ * [1] if someone ever added support for the old 2d cores, there could be
+ * more than one gpu object
+ */
struct list_head inactive_list;
+ struct mutex mm_lock;

/* worker for delayed free of objects: */
struct work_struct free_work;
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 3dcb2ef4740f..092ed152999e 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -768,13 +768,17 @@ int msm_gem_sync_object(struct drm_gem_object *obj,
void msm_gem_active_get(struct drm_gem_object *obj, struct msm_gpu *gpu)
{
struct msm_gem_object *msm_obj = to_msm_bo(obj);
- WARN_ON(!mutex_is_locked(&obj->dev->struct_mutex));
+ struct msm_drm_private *priv = obj->dev->dev_private;
+
+ might_sleep();
WARN_ON(msm_obj->madv != MSM_MADV_WILLNEED);

if (!atomic_fetch_inc(&msm_obj->active_count)) {
+ mutex_lock(&priv->mm_lock);
msm_obj->gpu = gpu;
list_del_init(&msm_obj->mm_list);
list_add_tail(&msm_obj->mm_list, &gpu->active_list);
+ mutex_unlock(&priv->mm_lock);
}
}

@@ -783,12 +787,14 @@ void msm_gem_active_put(struct drm_gem_object *obj)
struct msm_gem_object *msm_obj = to_msm_bo(obj);
struct msm_drm_private *priv = obj->dev->dev_private;

- WARN_ON(!mutex_is_locked(&obj->dev->struct_mutex));
+ might_sleep();

if (!atomic_dec_return(&msm_obj->active_count)) {
+ mutex_lock(&priv->mm_lock);
msm_obj->gpu = NULL;
list_del_init(&msm_obj->mm_list);
list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
+ mutex_unlock(&priv->mm_lock);
}
}

@@ -943,13 +949,16 @@ static void free_object(struct msm_gem_object *msm_obj)
{
struct drm_gem_object *obj = &msm_obj->base;
struct drm_device *dev = obj->dev;
+ struct msm_drm_private *priv = dev->dev_private;

WARN_ON(!mutex_is_locked(&dev->struct_mutex));

/* object should not be on active list: */
WARN_ON(is_active(msm_obj));

+ mutex_lock(&priv->mm_lock);
list_del(&msm_obj->mm_list);
+ mutex_unlock(&priv->mm_lock);

msm_gem_lock(obj);

@@ -1123,14 +1132,9 @@ static struct drm_gem_object *_msm_gem_new(struct drm_device *dev,
mapping_set_gfp_mask(obj->filp->f_mapping, GFP_HIGHUSER);
}

- if (struct_mutex_locked) {
- WARN_ON(!mutex_is_locked(&dev->struct_mutex));
- list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
- } else {
- mutex_lock(&dev->struct_mutex);
- list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
- mutex_unlock(&dev->struct_mutex);
- }
+ mutex_lock(&priv->mm_lock);
+ list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
+ mutex_unlock(&priv->mm_lock);

return obj;

@@ -1198,9 +1202,9 @@ struct drm_gem_object *msm_gem_import(struct drm_device *dev,

msm_gem_unlock(obj);

- mutex_lock(&dev->struct_mutex);
+ mutex_lock(&priv->mm_lock);
list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
- mutex_unlock(&dev->struct_mutex);
+ mutex_unlock(&priv->mm_lock);

return obj;

diff --git a/drivers/gpu/drm/msm/msm_gem_shrinker.c b/drivers/gpu/drm/msm/msm_gem_shrinker.c
index 2dc0ffa925b4..6be073b8ca08 100644
--- a/drivers/gpu/drm/msm/msm_gem_shrinker.c
+++ b/drivers/gpu/drm/msm/msm_gem_shrinker.c
@@ -51,6 +51,8 @@ msm_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
if (!msm_gem_shrinker_lock(dev, &unlock))
return 0;

+ mutex_lock(&priv->mm_lock);
+
list_for_each_entry(msm_obj, &priv->inactive_list, mm_list) {
if (!msm_gem_trylock(&msm_obj->base))
continue;
@@ -59,6 +61,8 @@ msm_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
msm_gem_unlock(&msm_obj->base);
}

+ mutex_unlock(&priv->mm_lock);
+
if (unlock)
mutex_unlock(&dev->struct_mutex);

@@ -78,6 +82,8 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
if (!msm_gem_shrinker_lock(dev, &unlock))
return SHRINK_STOP;

+ mutex_lock(&priv->mm_lock);
+
list_for_each_entry(msm_obj, &priv->inactive_list, mm_list) {
if (freed >= sc->nr_to_scan)
break;
@@ -90,6 +96,8 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
msm_gem_unlock(&msm_obj->base);
}

+ mutex_unlock(&priv->mm_lock);
+
if (unlock)
mutex_unlock(&dev->struct_mutex);

@@ -112,6 +120,8 @@ msm_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
if (!msm_gem_shrinker_lock(dev, &unlock))
return NOTIFY_DONE;

+ mutex_lock(&priv->mm_lock);
+
list_for_each_entry(msm_obj, &priv->inactive_list, mm_list) {
if (!msm_gem_trylock(&msm_obj->base))
continue;
@@ -129,6 +139,8 @@ msm_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
break;
}

+ mutex_unlock(&priv->mm_lock);
+
if (unlock)
mutex_unlock(&dev->struct_mutex);

diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index 6c9e1fdc1a76..1806e87600c0 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -94,7 +94,10 @@ struct msm_gpu {
struct msm_ringbuffer *rb[MSM_GPU_MAX_RINGS];
int nr_rings;

- /* list of GEM active objects: */
+ /*
+ * List of GEM active objects on this gpu. Protected by
+ * msm_drm_private::mm_lock
+ */
struct list_head active_list;

/* does gpu need hw_init? */
--
2.26.2