Re: [PATCH 04/14] drm/msm: Add priv->mm_lock to protect active/inactive lists

On Sun, Oct 4, 2020 at 3:15 PM Daniel Vetter daniel@ffwll.ch wrote:

On Sun, Oct 4, 2020 at 9:21 PM Rob Clark robdclark@gmail.com wrote:

...

From: Rob Clark robdclark@chromium.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@chromium.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.

Good idea..

(tbf, I have tested this with android+lockdep which pretty is great shrinker exercise.. but immediate notification of future problems is a good plan)

BR, -R