2022-11-13 23:48:42

by Dmitry Osipenko

Subject: [PATCH v1] drm/gem-vram: Fix deadlock in drm_gem_vram_vmap()

Recently DRM framebuffer core and all drivers were moved to unlocked
vmapping functions that take the reservation lock. The drm_gem_vram_vmap()
was missed out by accident and now deadlocks drivers that use drm_gem_vram
helpers when framebuffer is updated, like Bochs driver. Remove the locking
from drm_gem_vram_v[un]map() functions to fix the deadlock.

Reported-by: Dmitry Vyukov <[email protected]>
Fixes: 79e2cf2e7a19 ("drm/gem: Take reservation lock for vmap/vunmap operations")
Signed-off-by: Dmitry Osipenko <[email protected]>
---
drivers/gpu/drm/drm_gem_vram_helper.c | 18 +++---------------
1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
index 125160b534be..b6c7e3803bb3 100644
--- a/drivers/gpu/drm/drm_gem_vram_helper.c
+++ b/drivers/gpu/drm/drm_gem_vram_helper.c
@@ -433,25 +433,19 @@ int drm_gem_vram_vmap(struct drm_gem_vram_object *gbo, struct iosys_map *map)
{
int ret;

- ret = ttm_bo_reserve(&gbo->bo, true, false, NULL);
- if (ret)
- return ret;
+ dma_resv_assert_held(gbo->bo.base.resv);

ret = drm_gem_vram_pin_locked(gbo, 0);
if (ret)
- goto err_ttm_bo_unreserve;
+ return ret;
ret = drm_gem_vram_kmap_locked(gbo, map);
if (ret)
goto err_drm_gem_vram_unpin_locked;

- ttm_bo_unreserve(&gbo->bo);
-
return 0;

err_drm_gem_vram_unpin_locked:
drm_gem_vram_unpin_locked(gbo);
-err_ttm_bo_unreserve:
- ttm_bo_unreserve(&gbo->bo);
return ret;
}
EXPORT_SYMBOL(drm_gem_vram_vmap);
@@ -467,16 +461,10 @@ EXPORT_SYMBOL(drm_gem_vram_vmap);
void drm_gem_vram_vunmap(struct drm_gem_vram_object *gbo,
struct iosys_map *map)
{
- int ret;
-
- ret = ttm_bo_reserve(&gbo->bo, false, false, NULL);
- if (WARN_ONCE(ret, "ttm_bo_reserve_failed(): ret=%d\n", ret))
- return;
+ dma_resv_assert_held(gbo->bo.base.resv);

drm_gem_vram_kunmap_locked(gbo, map);
drm_gem_vram_unpin_locked(gbo);
-
- ttm_bo_unreserve(&gbo->bo);
}
EXPORT_SYMBOL(drm_gem_vram_vunmap);

--
2.37.3

2022-11-14 10:40:14

by Christian König

Subject: Re: [PATCH v1] drm/gem-vram: Fix deadlock in drm_gem_vram_vmap()

Am 14.11.22 um 00:38 schrieb Dmitry Osipenko:
> Recently DRM framebuffer core and all drivers were moved to unlocked
> vmapping functions that take the reservation lock. The drm_gem_vram_vmap()
> was missed out by accident and now deadlocks drivers that use drm_gem_vram
> helpers when framebuffer is updated, like Bochs driver. Remove the locking
> from drm_gem_vram_v[un]map() functions to fix the deadlock.
>
> Reported-by: Dmitry Vyukov <[email protected]>
> Fixes: 79e2cf2e7a19 ("drm/gem: Take reservation lock for vmap/vunmap operations")
> Signed-off-by: Dmitry Osipenko <[email protected]>

Reviewed-by: Christian König <[email protected]

> ---
> drivers/gpu/drm/drm_gem_vram_helper.c | 18 +++---------------
> 1 file changed, 3 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
> index 125160b534be..b6c7e3803bb3 100644
> --- a/drivers/gpu/drm/drm_gem_vram_helper.c
> +++ b/drivers/gpu/drm/drm_gem_vram_helper.c
> @@ -433,25 +433,19 @@ int drm_gem_vram_vmap(struct drm_gem_vram_object *gbo, struct iosys_map *map)
> {
> int ret;
>
> - ret = ttm_bo_reserve(&gbo->bo, true, false, NULL);
> - if (ret)
> - return ret;
> + dma_resv_assert_held(gbo->bo.base.resv);
>
> ret = drm_gem_vram_pin_locked(gbo, 0);
> if (ret)
> - goto err_ttm_bo_unreserve;
> + return ret;
> ret = drm_gem_vram_kmap_locked(gbo, map);
> if (ret)
> goto err_drm_gem_vram_unpin_locked;
>
> - ttm_bo_unreserve(&gbo->bo);
> -
> return 0;
>
> err_drm_gem_vram_unpin_locked:
> drm_gem_vram_unpin_locked(gbo);
> -err_ttm_bo_unreserve:
> - ttm_bo_unreserve(&gbo->bo);
> return ret;
> }
> EXPORT_SYMBOL(drm_gem_vram_vmap);
> @@ -467,16 +461,10 @@ EXPORT_SYMBOL(drm_gem_vram_vmap);
> void drm_gem_vram_vunmap(struct drm_gem_vram_object *gbo,
> struct iosys_map *map)
> {
> - int ret;
> -
> - ret = ttm_bo_reserve(&gbo->bo, false, false, NULL);
> - if (WARN_ONCE(ret, "ttm_bo_reserve_failed(): ret=%d\n", ret))
> - return;
> + dma_resv_assert_held(gbo->bo.base.resv);
>
> drm_gem_vram_kunmap_locked(gbo, map);
> drm_gem_vram_unpin_locked(gbo);
> -
> - ttm_bo_unreserve(&gbo->bo);
> }
> EXPORT_SYMBOL(drm_gem_vram_vunmap);
>

2022-11-14 13:27:24

by Dmitry Osipenko

Subject: Re: [PATCH v1] drm/gem-vram: Fix deadlock in drm_gem_vram_vmap()

On 11/14/22 02:38, Dmitry Osipenko wrote:
> Recently DRM framebuffer core and all drivers were moved to unlocked
> vmapping functions that take the reservation lock. The drm_gem_vram_vmap()
> was missed out by accident and now deadlocks drivers that use drm_gem_vram
> helpers when framebuffer is updated, like Bochs driver. Remove the locking
> from drm_gem_vram_v[un]map() functions to fix the deadlock.
>
> Reported-by: Dmitry Vyukov <[email protected]>
> Fixes: 79e2cf2e7a19 ("drm/gem: Take reservation lock for vmap/vunmap operations")
> Signed-off-by: Dmitry Osipenko <[email protected]>
> ---
> drivers/gpu/drm/drm_gem_vram_helper.c | 18 +++---------------
> 1 file changed, 3 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
> index 125160b534be..b6c7e3803bb3 100644
> --- a/drivers/gpu/drm/drm_gem_vram_helper.c
> +++ b/drivers/gpu/drm/drm_gem_vram_helper.c
> @@ -433,25 +433,19 @@ int drm_gem_vram_vmap(struct drm_gem_vram_object *gbo, struct iosys_map *map)
> {
> int ret;
>
> - ret = ttm_bo_reserve(&gbo->bo, true, false, NULL);
> - if (ret)
> - return ret;
> + dma_resv_assert_held(gbo->bo.base.resv);
>
> ret = drm_gem_vram_pin_locked(gbo, 0);
> if (ret)
> - goto err_ttm_bo_unreserve;
> + return ret;
> ret = drm_gem_vram_kmap_locked(gbo, map);
> if (ret)
> goto err_drm_gem_vram_unpin_locked;
>
> - ttm_bo_unreserve(&gbo->bo);
> -
> return 0;
>
> err_drm_gem_vram_unpin_locked:
> drm_gem_vram_unpin_locked(gbo);
> -err_ttm_bo_unreserve:
> - ttm_bo_unreserve(&gbo->bo);
> return ret;
> }
> EXPORT_SYMBOL(drm_gem_vram_vmap);
> @@ -467,16 +461,10 @@ EXPORT_SYMBOL(drm_gem_vram_vmap);
> void drm_gem_vram_vunmap(struct drm_gem_vram_object *gbo,
> struct iosys_map *map)
> {
> - int ret;
> -
> - ret = ttm_bo_reserve(&gbo->bo, false, false, NULL);
> - if (WARN_ONCE(ret, "ttm_bo_reserve_failed(): ret=%d\n", ret))
> - return;
> + dma_resv_assert_held(gbo->bo.base.resv);
>
> drm_gem_vram_kunmap_locked(gbo, map);
> drm_gem_vram_unpin_locked(gbo);
> -
> - ttm_bo_unreserve(&gbo->bo);
> }
> EXPORT_SYMBOL(drm_gem_vram_vunmap);
>

Applied to drm-misc-next

--
Best regards,
Dmitry