On Wed, Jul 21, 2021 at 10:23:57AM -0500, Jason Ekstrand wrote:
> We create a bunch of debugfs entries as a side-effect of
> ttm_global_init() and then never clean them up. This isn't usually a
> problem because we free the whole debugfs directory on module unload.
> However, if the global reference count ever goes to zero and then
> ttm_global_init() is called again, we'll re-create those debugfs entries
> and debugfs will complain in dmesg that we're creating entries that
> already exist. This patch fixes this problem by changing the lifetime
> of the whole TTM debugfs directory to match that of the TTM global
> state.
>
> Signed-off-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
I've pushed this to drm-misc-fixes since I think this entire slab debugfs
story started with 5.15-rc1, so good to get it sorted there.
-Daniel
> ---
> drivers/gpu/drm/ttm/ttm_device.c | 12 ++++++++++++
> drivers/gpu/drm/ttm/ttm_module.c | 16 ----------------
> 2 files changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
> index 519deea8e39b7..74e3b460132b3 100644
> --- a/drivers/gpu/drm/ttm/ttm_device.c
> +++ b/drivers/gpu/drm/ttm/ttm_device.c
> @@ -44,6 +44,8 @@ static unsigned ttm_glob_use_count;
> struct ttm_global ttm_glob;
> EXPORT_SYMBOL(ttm_glob);
>
> +struct dentry *ttm_debugfs_root;
> +
> static void ttm_global_release(void)
> {
> struct ttm_global *glob = &ttm_glob;
> @@ -53,6 +55,7 @@ static void ttm_global_release(void)
> goto out;
>
> ttm_pool_mgr_fini();
> + debugfs_remove(ttm_debugfs_root);
>
> __free_page(glob->dummy_read_page);
> memset(glob, 0, sizeof(*glob));
> @@ -73,6 +76,13 @@ static int ttm_global_init(void)
>
> si_meminfo(&si);
>
> + ttm_debugfs_root = debugfs_create_dir("ttm", NULL);
> + if (IS_ERR(ttm_debugfs_root)) {
> + ret = PTR_ERR(ttm_debugfs_root);
> + ttm_debugfs_root = NULL;
> + goto out;
> + }
> +
> /* Limit the number of pages in the pool to about 50% of the total
> * system memory.
> */
> @@ -100,6 +110,8 @@ static int ttm_global_init(void)
> debugfs_create_atomic_t("buffer_objects", 0444, ttm_debugfs_root,
> &glob->bo_count);
> out:
> + if (ret && ttm_debugfs_root)
> + debugfs_remove(ttm_debugfs_root);
> if (ret)
> --ttm_glob_use_count;
> mutex_unlock(&ttm_global_mutex);
> diff --git a/drivers/gpu/drm/ttm/ttm_module.c b/drivers/gpu/drm/ttm/ttm_module.c
> index 997c458f68a9a..7fcdef278c742 100644
> --- a/drivers/gpu/drm/ttm/ttm_module.c
> +++ b/drivers/gpu/drm/ttm/ttm_module.c
> @@ -72,22 +72,6 @@ pgprot_t ttm_prot_from_caching(enum ttm_caching caching, pgprot_t tmp)
> return tmp;
> }
>
> -struct dentry *ttm_debugfs_root;
> -
> -static int __init ttm_init(void)
> -{
> - ttm_debugfs_root = debugfs_create_dir("ttm", NULL);
> - return 0;
> -}
> -
> -static void __exit ttm_exit(void)
> -{
> - debugfs_remove(ttm_debugfs_root);
> -}
> -
> -module_init(ttm_init);
> -module_exit(ttm_exit);
> -
> MODULE_AUTHOR("Thomas Hellstrom, Jerome Glisse");
> MODULE_DESCRIPTION("TTM memory manager subsystem (for DRM device)");
> MODULE_LICENSE("GPL and additional rights");
> --
> 2.31.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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