| Message ID | 20190823021216.5862-7-robh@kernel.org |
|---|---|
| State | Accepted |
| Commit | 55b9a0549e4303ca43481f9ba2cdfa305277d97d |
| Headers | show |
| Series | [v2,1/8] drm/panfrost: Fix possible suspend in panfrost_remove | expand |
On 23/08/2019 03:12, Rob Herring wrote: > Lockdep reports a circular locking dependency with pages_lock taken in > the shrinker callback. The deadlock can't actually happen with current > users at least as a BO will never be purgeable when pages_lock is held. > To be safe, let's use mutex_trylock() instead and bail if a BO is locked > already. > > Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com> > Cc: Steven Price <steven.price@arm.com> > Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com> > Cc: David Airlie <airlied@linux.ie> > Cc: Daniel Vetter <daniel@ffwll.ch> > Signed-off-by: Rob Herring <robh@kernel.org> Reviewed-by: Steven Price <steven.price@arm.com> > --- > v2: new patch > > drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c > index d191632b6197..458f0fa68111 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c > +++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c > @@ -36,15 +36,18 @@ panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc > return count; > } > > -static void panfrost_gem_purge(struct drm_gem_object *obj) > +static bool panfrost_gem_purge(struct drm_gem_object *obj) > { > struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); > - mutex_lock(&shmem->pages_lock); > + > + if (!mutex_trylock(&shmem->pages_lock)) > + return false; > > panfrost_mmu_unmap(to_panfrost_bo(obj)); > drm_gem_shmem_purge_locked(obj); > > mutex_unlock(&shmem->pages_lock); > + return true; > } > > static unsigned long > @@ -61,8 +64,8 @@ panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc) > list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) { > if (freed >= sc->nr_to_scan) > break; > - if (drm_gem_shmem_is_purgeable(shmem)) { > - panfrost_gem_purge(&shmem->base); > + if (drm_gem_shmem_is_purgeable(shmem) && > + panfrost_gem_purge(&shmem->base)) { > freed += shmem->base.size >> PAGE_SHIFT; > list_del_init(&shmem->madv_list); > } >
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c index d191632b6197..458f0fa68111 100644 --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c +++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c @@ -36,15 +36,18 @@ panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc return count; } -static void panfrost_gem_purge(struct drm_gem_object *obj) +static bool panfrost_gem_purge(struct drm_gem_object *obj) { struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); - mutex_lock(&shmem->pages_lock); + + if (!mutex_trylock(&shmem->pages_lock)) + return false; panfrost_mmu_unmap(to_panfrost_bo(obj)); drm_gem_shmem_purge_locked(obj); mutex_unlock(&shmem->pages_lock); + return true; } static unsigned long @@ -61,8 +64,8 @@ panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc) list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) { if (freed >= sc->nr_to_scan) break; - if (drm_gem_shmem_is_purgeable(shmem)) { - panfrost_gem_purge(&shmem->base); + if (drm_gem_shmem_is_purgeable(shmem) && + panfrost_gem_purge(&shmem->base)) { freed += shmem->base.size >> PAGE_SHIFT; list_del_init(&shmem->madv_list); }
Lockdep reports a circular locking dependency with pages_lock taken in the shrinker callback. The deadlock can't actually happen with current users at least as a BO will never be purgeable when pages_lock is held. To be safe, let's use mutex_trylock() instead and bail if a BO is locked already. Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com> Cc: Steven Price <steven.price@arm.com> Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com> Cc: David Airlie <airlied@linux.ie> Cc: Daniel Vetter <daniel@ffwll.ch> Signed-off-by: Rob Herring <robh@kernel.org> --- v2: new patch drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)