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Message-ID: <CAKMK7uHrP1ijVORpW0xvMX4M_0HQpfzUk2bE576gpzSPug-M6A@mail.gmail.com>
Date: Mon, 5 Oct 2020 00:15:24 +0200
From: Daniel Vetter <daniel@...ll.ch>
To: Rob Clark <robdclark@...il.com>
Cc: dri-devel <dri-devel@...ts.freedesktop.org>,
Rob Clark <robdclark@...omium.org>,
Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
"open list:DRM DRIVER FOR MSM ADRENO GPU"
<linux-arm-msm@...r.kernel.org>,
"open list:DRM DRIVER FOR MSM ADRENO GPU"
<freedreno@...ts.freedesktop.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 04/14] drm/msm: Add priv->mm_lock to protect
active/inactive lists
On Sun, Oct 4, 2020 at 9:21 PM Rob Clark <robdclark@...il.com> wrote:
>
> From: Rob Clark <robdclark@...omium.org>
>
> 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@...omium.org>
> ---
> drivers/gpu/drm/msm/msm_debugfs.c | 7 +++++++
> drivers/gpu/drm/msm/msm_drv.c | 1 +
> 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, 52 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 49685571dc0e..dc6efc089285 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/drivers/gpu/drm/msm/msm_drv.c
> @@ -441,6 +441,7 @@ 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);
I highly recommend you drop a
fs_reclaim_acquire(GFP_KERNEL);
might_lock(&priv->mm_lock);
fs_reclaim_release(GFP_KERNEL);
in here to teach lockdep about your ordering against the shrinker.
Gives you full testing every boot, even if your shrinker never gets
called.
-Daniel
>
> drm_mode_config_init(ddev);
>
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index b9dd8f8f4887..50978e5db376 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 a870b3ad129d..b04ed8b52f9d 100644
> --- a/drivers/gpu/drm/msm/msm_gem.c
> +++ b/drivers/gpu/drm/msm/msm_gem.c
> @@ -746,13 +746,17 @@ 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);
> }
> }
>
> @@ -761,12 +765,14 @@ 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);
> }
> }
>
> @@ -921,13 +927,16 @@ 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);
>
> mutex_lock(&msm_obj->lock);
>
> @@ -1103,14 +1112,9 @@ 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;
>
> @@ -1178,9 +1182,9 @@ struct drm_gem_object *msm_gem_import(struct drm_device *dev,
>
> mutex_unlock(&msm_obj->lock);
>
> - 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 482576d7a39a..c41b84a3a484 100644
> --- a/drivers/gpu/drm/msm/msm_gem_shrinker.c
> +++ b/drivers/gpu/drm/msm/msm_gem_shrinker.c
> @@ -51,11 +51,15 @@ 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 (is_purgeable(msm_obj))
> count += msm_obj->base.size >> PAGE_SHIFT;
> }
>
> + mutex_unlock(&priv->mm_lock);
> +
> if (unlock)
> mutex_unlock(&dev->struct_mutex);
>
> @@ -75,6 +79,8 @@ 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;
> @@ -84,6 +90,8 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
> }
> }
>
> + mutex_unlock(&priv->mm_lock);
> +
> if (unlock)
> mutex_unlock(&dev->struct_mutex);
>
> @@ -106,6 +114,8 @@ 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 (is_vunmapable(msm_obj)) {
> msm_gem_vunmap(&msm_obj->base, OBJ_LOCK_SHRINKER);
> @@ -118,6 +128,8 @@ msm_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
> }
> }
>
> + 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
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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