drm/panfrost: Use mutex_trylock in panfrost_gem_purge
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: 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> Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190823021216.5862-7-robh@kernel.org
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@ -36,15 +36,18 @@ panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc
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return count;
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return count;
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}
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}
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static void panfrost_gem_purge(struct drm_gem_object *obj)
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static bool panfrost_gem_purge(struct drm_gem_object *obj)
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{
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{
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struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
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struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
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mutex_lock(&shmem->pages_lock);
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if (!mutex_trylock(&shmem->pages_lock))
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return false;
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panfrost_mmu_unmap(to_panfrost_bo(obj));
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panfrost_mmu_unmap(to_panfrost_bo(obj));
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drm_gem_shmem_purge_locked(obj);
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drm_gem_shmem_purge_locked(obj);
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mutex_unlock(&shmem->pages_lock);
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mutex_unlock(&shmem->pages_lock);
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return true;
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}
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}
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static unsigned long
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static unsigned long
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@ -61,8 +64,8 @@ panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
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list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
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list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
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if (freed >= sc->nr_to_scan)
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if (freed >= sc->nr_to_scan)
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break;
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break;
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if (drm_gem_shmem_is_purgeable(shmem)) {
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if (drm_gem_shmem_is_purgeable(shmem) &&
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panfrost_gem_purge(&shmem->base);
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panfrost_gem_purge(&shmem->base)) {
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freed += shmem->base.size >> PAGE_SHIFT;
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freed += shmem->base.size >> PAGE_SHIFT;
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list_del_init(&shmem->madv_list);
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list_del_init(&shmem->madv_list);
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}
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}
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