On Wed, Aug 14, 2019 at 07:26:44PM +0100, Chris Wilson wrote:
> Quoting Chris Wilson (2019-08-14 19:24:01)
> > This reverts
> > 67c97fb79a7f ("dma-buf: add reservation_object_fences helper")
> > dd7a7d1ff2f1 ("drm/i915: use new reservation_object_fences helper")
> > 0e1d8083bddb ("dma-buf: further relax reservation_object_add_shared_fence")
> > 5d344f58da76 ("dma-buf: nuke reservation_object seq number")
Oh I didn't realize they landed already.
> > The scenario that defeats simply grabbing a set of shared/exclusive
> > fences and using them blissfully under RCU is that any of those fences
> > may be reallocated by a SLAB_TYPESAFE_BY_RCU fence slab cache. In this
> > scenario, while keeping the rcu_read_lock we need to establish that no
> > fence was changed in the dma_resv after a read (or full) memory barrier.
So if I'm reading correctly what Chris is saying here I guess my half
comment in that other thread pointed at a real oversight. Since I still
haven't checked and it's too late for real review not more for now.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>
> I said I needed to go lie down, that proves it.
Yeah I guess we need to wait for Christian to wake up an have a working
brain.
-Daniel
>
> Cc: Christian König <christian.koenig@xxxxxxx>
>
> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > ---
> > drivers/dma-buf/dma-buf.c | 31 ++++-
> > drivers/dma-buf/dma-resv.c | 109 ++++++++++++-----
> > .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 7 +-
> > drivers/gpu/drm/i915/gem/i915_gem_busy.c | 24 ++--
> > include/linux/dma-resv.h | 113 ++++++++----------
> > 5 files changed, 175 insertions(+), 109 deletions(-)
> >
> > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> > index b3400d6524ab..433d91d710e4 100644
> > --- a/drivers/dma-buf/dma-buf.c
> > +++ b/drivers/dma-buf/dma-buf.c
> > @@ -199,7 +199,7 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
> > struct dma_resv_list *fobj;
> > struct dma_fence *fence_excl;
> > __poll_t events;
> > - unsigned shared_count;
> > + unsigned shared_count, seq;
> >
> > dmabuf = file->private_data;
> > if (!dmabuf || !dmabuf->resv)
> > @@ -213,8 +213,21 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
> > if (!events)
> > return 0;
> >
> > +retry:
> > + seq = read_seqcount_begin(&resv->seq);
> > rcu_read_lock();
> > - dma_resv_fences(resv, &fence_excl, &fobj, &shared_count);
> > +
> > + fobj = rcu_dereference(resv->fence);
> > + if (fobj)
> > + shared_count = fobj->shared_count;
> > + else
> > + shared_count = 0;
> > + fence_excl = rcu_dereference(resv->fence_excl);
> > + if (read_seqcount_retry(&resv->seq, seq)) {
> > + rcu_read_unlock();
> > + goto retry;
> > + }
> > +
> > if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
> > struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
> > __poll_t pevents = EPOLLIN;
> > @@ -1144,6 +1157,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
> > struct dma_resv *robj;
> > struct dma_resv_list *fobj;
> > struct dma_fence *fence;
> > + unsigned seq;
> > int count = 0, attach_count, shared_count, i;
> > size_t size = 0;
> >
> > @@ -1174,9 +1188,16 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
> > buf_obj->name ?: "");
> >
> > robj = buf_obj->resv;
> > - rcu_read_lock();
> > - dma_resv_fences(robj, &fence, &fobj, &shared_count);
> > - rcu_read_unlock();
> > + while (true) {
> > + seq = read_seqcount_begin(&robj->seq);
> > + rcu_read_lock();
> > + fobj = rcu_dereference(robj->fence);
> > + shared_count = fobj ? fobj->shared_count : 0;
> > + fence = rcu_dereference(robj->fence_excl);
> > + if (!read_seqcount_retry(&robj->seq, seq))
> > + break;
> > + rcu_read_unlock();
> > + }
> >
> > if (fence)
> > seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
> > diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
> > index f5142683c851..42a8f3f11681 100644
> > --- a/drivers/dma-buf/dma-resv.c
> > +++ b/drivers/dma-buf/dma-resv.c
> > @@ -49,6 +49,12 @@
> > DEFINE_WD_CLASS(reservation_ww_class);
> > EXPORT_SYMBOL(reservation_ww_class);
> >
> > +struct lock_class_key reservation_seqcount_class;
> > +EXPORT_SYMBOL(reservation_seqcount_class);
> > +
> > +const char reservation_seqcount_string[] = "reservation_seqcount";
> > +EXPORT_SYMBOL(reservation_seqcount_string);
> > +
> > /**
> > * dma_resv_list_alloc - allocate fence list
> > * @shared_max: number of fences we need space for
> > @@ -96,6 +102,9 @@ static void dma_resv_list_free(struct dma_resv_list *list)
> > void dma_resv_init(struct dma_resv *obj)
> > {
> > ww_mutex_init(&obj->lock, &reservation_ww_class);
> > +
> > + __seqcount_init(&obj->seq, reservation_seqcount_string,
> > + &reservation_seqcount_class);
> > RCU_INIT_POINTER(obj->fence, NULL);
> > RCU_INIT_POINTER(obj->fence_excl, NULL);
> > }
> > @@ -225,6 +234,9 @@ void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
> > fobj = dma_resv_get_list(obj);
> > count = fobj->shared_count;
> >
> > + preempt_disable();
> > + write_seqcount_begin(&obj->seq);
> > +
> > for (i = 0; i < count; ++i) {
> >
> > old = rcu_dereference_protected(fobj->shared[i],
> > @@ -242,6 +254,9 @@ void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
> > RCU_INIT_POINTER(fobj->shared[i], fence);
> > /* pointer update must be visible before we extend the shared_count */
> > smp_store_mb(fobj->shared_count, count);
> > +
> > + write_seqcount_end(&obj->seq);
> > + preempt_enable();
> > dma_fence_put(old);
> > }
> > EXPORT_SYMBOL(dma_resv_add_shared_fence);
> > @@ -269,10 +284,12 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
> > dma_fence_get(fence);
> >
> > preempt_disable();
> > - rcu_assign_pointer(obj->fence_excl, fence);
> > - /* pointer update must be visible before we modify the shared_count */
> > + write_seqcount_begin(&obj->seq);
> > + /* write_seqcount_begin provides the necessary memory barrier */
> > + RCU_INIT_POINTER(obj->fence_excl, fence);
> > if (old)
> > - smp_store_mb(old->shared_count, 0);
> > + old->shared_count = 0;
> > + write_seqcount_end(&obj->seq);
> > preempt_enable();
> >
> > /* inplace update, no shared fences */
> > @@ -295,15 +312,17 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
> > {
> > struct dma_resv_list *src_list, *dst_list;
> > struct dma_fence *old, *new;
> > - unsigned int i, shared_count;
> > + unsigned i;
> >
> > dma_resv_assert_held(dst);
> >
> > rcu_read_lock();
> > + src_list = rcu_dereference(src->fence);
> >
> > retry:
> > - dma_resv_fences(src, &new, &src_list, &shared_count);
> > - if (shared_count) {
> > + if (src_list) {
> > + unsigned shared_count = src_list->shared_count;
> > +
> > rcu_read_unlock();
> >
> > dst_list = dma_resv_list_alloc(shared_count);
> > @@ -311,14 +330,14 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
> > return -ENOMEM;
> >
> > rcu_read_lock();
> > - dma_resv_fences(src, &new, &src_list, &shared_count);
> > - if (!src_list || shared_count > dst_list->shared_max) {
> > + src_list = rcu_dereference(src->fence);
> > + if (!src_list || src_list->shared_count > shared_count) {
> > kfree(dst_list);
> > goto retry;
> > }
> >
> > dst_list->shared_count = 0;
> > - for (i = 0; i < shared_count; ++i) {
> > + for (i = 0; i < src_list->shared_count; ++i) {
> > struct dma_fence *fence;
> >
> > fence = rcu_dereference(src_list->shared[i]);
> > @@ -328,6 +347,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
> >
> > if (!dma_fence_get_rcu(fence)) {
> > dma_resv_list_free(dst_list);
> > + src_list = rcu_dereference(src->fence);
> > goto retry;
> > }
> >
> > @@ -342,18 +362,18 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
> > dst_list = NULL;
> > }
> >
> > - if (new && !dma_fence_get_rcu(new)) {
> > - dma_resv_list_free(dst_list);
> > - goto retry;
> > - }
> > + new = dma_fence_get_rcu_safe(&src->fence_excl);
> > rcu_read_unlock();
> >
> > src_list = dma_resv_get_list(dst);
> > old = dma_resv_get_excl(dst);
> >
> > preempt_disable();
> > - rcu_assign_pointer(dst->fence_excl, new);
> > - rcu_assign_pointer(dst->fence, dst_list);
> > + write_seqcount_begin(&dst->seq);
> > + /* write_seqcount_begin provides the necessary memory barrier */
> > + RCU_INIT_POINTER(dst->fence_excl, new);
> > + RCU_INIT_POINTER(dst->fence, dst_list);
> > + write_seqcount_end(&dst->seq);
> > preempt_enable();
> >
> > dma_resv_list_free(src_list);
> > @@ -388,18 +408,19 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
> >
> > do {
> > struct dma_resv_list *fobj;
> > - unsigned int i;
> > + unsigned int i, seq;
> > size_t sz = 0;
> >
> > - i = 0;
> > + shared_count = i = 0;
> >
> > rcu_read_lock();
> > - dma_resv_fences(obj, &fence_excl, &fobj,
> > - &shared_count);
> > + seq = read_seqcount_begin(&obj->seq);
> >
> > + fence_excl = rcu_dereference(obj->fence_excl);
> > if (fence_excl && !dma_fence_get_rcu(fence_excl))
> > goto unlock;
> >
> > + fobj = rcu_dereference(obj->fence);
> > if (fobj)
> > sz += sizeof(*shared) * fobj->shared_max;
> >
> > @@ -427,6 +448,7 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
> > break;
> > }
> > shared = nshared;
> > + shared_count = fobj ? fobj->shared_count : 0;
> > for (i = 0; i < shared_count; ++i) {
> > shared[i] = rcu_dereference(fobj->shared[i]);
> > if (!dma_fence_get_rcu(shared[i]))
> > @@ -434,7 +456,7 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
> > }
> > }
> >
> > - if (i != shared_count) {
> > + if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
> > while (i--)
> > dma_fence_put(shared[i]);
> > dma_fence_put(fence_excl);
> > @@ -478,17 +500,18 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
> > bool wait_all, bool intr,
> > unsigned long timeout)
> > {
> > - struct dma_resv_list *fobj;
> > struct dma_fence *fence;
> > - unsigned shared_count;
> > + unsigned seq, shared_count;
> > long ret = timeout ? timeout : 1;
> > int i;
> >
> > retry:
> > + shared_count = 0;
> > + seq = read_seqcount_begin(&obj->seq);
> > rcu_read_lock();
> > i = -1;
> >
> > - dma_resv_fences(obj, &fence, &fobj, &shared_count);
> > + fence = rcu_dereference(obj->fence_excl);
> > if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
> > if (!dma_fence_get_rcu(fence))
> > goto unlock_retry;
> > @@ -503,6 +526,11 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
> > }
> >
> > if (wait_all) {
> > + struct dma_resv_list *fobj = rcu_dereference(obj->fence);
> > +
> > + if (fobj)
> > + shared_count = fobj->shared_count;
> > +
> > for (i = 0; !fence && i < shared_count; ++i) {
> > struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
> >
> > @@ -525,6 +553,11 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
> >
> > rcu_read_unlock();
> > if (fence) {
> > + if (read_seqcount_retry(&obj->seq, seq)) {
> > + dma_fence_put(fence);
> > + goto retry;
> > + }
> > +
> > ret = dma_fence_wait_timeout(fence, intr, ret);
> > dma_fence_put(fence);
> > if (ret > 0 && wait_all && (i + 1 < shared_count))
> > @@ -567,19 +600,23 @@ static inline int dma_resv_test_signaled_single(struct dma_fence *passed_fence)
> > */
> > bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
> > {
> > - struct dma_resv_list *fobj;
> > - struct dma_fence *fence_excl;
> > - unsigned shared_count;
> > + unsigned seq, shared_count;
> > int ret;
> >
> > rcu_read_lock();
> > retry:
> > ret = true;
> > + shared_count = 0;
> > + seq = read_seqcount_begin(&obj->seq);
> >
> > - dma_resv_fences(obj, &fence_excl, &fobj, &shared_count);
> > if (test_all) {
> > unsigned i;
> >
> > + struct dma_resv_list *fobj = rcu_dereference(obj->fence);
> > +
> > + if (fobj)
> > + shared_count = fobj->shared_count;
> > +
> > for (i = 0; i < shared_count; ++i) {
> > struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
> >
> > @@ -589,14 +626,24 @@ bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
> > else if (!ret)
> > break;
> > }
> > - }
> >
> > - if (!shared_count && fence_excl) {
> > - ret = dma_resv_test_signaled_single(fence_excl);
> > - if (ret < 0)
> > + if (read_seqcount_retry(&obj->seq, seq))
> > goto retry;
> > }
> >
> > + if (!shared_count) {
> > + struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
> > +
> > + if (fence_excl) {
> > + ret = dma_resv_test_signaled_single(fence_excl);
> > + if (ret < 0)
> > + goto retry;
> > +
> > + if (read_seqcount_retry(&obj->seq, seq))
> > + goto retry;
> > + }
> > + }
> > +
> > rcu_read_unlock();
> > return ret;
> > }
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > index bc4ec6b20a87..76e3516484e7 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > @@ -251,7 +251,12 @@ static int amdgpu_amdkfd_remove_eviction_fence(struct amdgpu_bo *bo,
> > new->shared_max = old->shared_max;
> > new->shared_count = k;
> >
> > - rcu_assign_pointer(resv->fence, new);
> > + /* Install the new fence list, seqcount provides the barriers */
> > + preempt_disable();
> > + write_seqcount_begin(&resv->seq);
> > + RCU_INIT_POINTER(resv->fence, new);
> > + write_seqcount_end(&resv->seq);
> > + preempt_enable();
> >
> > /* Drop the references to the removed fences or move them to ef_list */
> > for (i = j, k = 0; i < old->shared_count; ++i) {
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
> > index a2aff1d8290e..3d4f5775a4ba 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
> > @@ -83,8 +83,7 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
> > struct drm_i915_gem_busy *args = data;
> > struct drm_i915_gem_object *obj;
> > struct dma_resv_list *list;
> > - unsigned int i, shared_count;
> > - struct dma_fence *excl;
> > + unsigned int seq;
> > int err;
> >
> > err = -ENOENT;
> > @@ -110,18 +109,29 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
> > * to report the overall busyness. This is what the wait-ioctl does.
> > *
> > */
> > - dma_resv_fences(obj->base.resv, &excl, &list, &shared_count);
> > +retry:
> > + seq = raw_read_seqcount(&obj->base.resv->seq);
> >
> > /* Translate the exclusive fence to the READ *and* WRITE engine */
> > - args->busy = busy_check_writer(excl);
> > + args->busy =
> > + busy_check_writer(rcu_dereference(obj->base.resv->fence_excl));
> >
> > /* Translate shared fences to READ set of engines */
> > - for (i = 0; i < shared_count; ++i) {
> > - struct dma_fence *fence = rcu_dereference(list->shared[i]);
> > + list = rcu_dereference(obj->base.resv->fence);
> > + if (list) {
> > + unsigned int shared_count = list->shared_count, i;
> >
> > - args->busy |= busy_check_reader(fence);
> > + for (i = 0; i < shared_count; ++i) {
> > + struct dma_fence *fence =
> > + rcu_dereference(list->shared[i]);
> > +
> > + args->busy |= busy_check_reader(fence);
> > + }
> > }
> >
> > + if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq))
> > + goto retry;
> > +
> > err = 0;
> > out:
> > rcu_read_unlock();
> > diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
> > index 38f2802afabb..ee50d10f052b 100644
> > --- a/include/linux/dma-resv.h
> > +++ b/include/linux/dma-resv.h
> > @@ -46,6 +46,8 @@
> > #include <linux/rcupdate.h>
> >
> > extern struct ww_class reservation_ww_class;
> > +extern struct lock_class_key reservation_seqcount_class;
> > +extern const char reservation_seqcount_string[];
> >
> > /**
> > * struct dma_resv_list - a list of shared fences
> > @@ -69,6 +71,7 @@ struct dma_resv_list {
> > */
> > struct dma_resv {
> > struct ww_mutex lock;
> > + seqcount_t seq;
> >
> > struct dma_fence __rcu *fence_excl;
> > struct dma_resv_list __rcu *fence;
> > @@ -77,24 +80,6 @@ struct dma_resv {
> > #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
> > #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)
> >
> > -/**
> > - * dma_resv_get_excl - get the reservation object's
> > - * exclusive fence, with update-side lock held
> > - * @obj: the reservation object
> > - *
> > - * Returns the exclusive fence (if any). Does NOT take a
> > - * reference. Writers must hold obj->lock, readers may only
> > - * hold a RCU read side lock.
> > - *
> > - * RETURNS
> > - * The exclusive fence or NULL
> > - */
> > -static inline struct dma_fence *dma_resv_get_excl(struct dma_resv *obj)
> > -{
> > - return rcu_dereference_protected(obj->fence_excl,
> > - dma_resv_held(obj));
> > -}
> > -
> > /**
> > * dma_resv_get_list - get the reservation object's
> > * shared fence list, with update-side lock held
> > @@ -109,53 +94,6 @@ static inline struct dma_resv_list *dma_resv_get_list(struct dma_resv *obj)
> > dma_resv_held(obj));
> > }
> >
> > -/**
> > - * dma_resv_fences - read consistent fence pointers
> > - * @obj: reservation object where we get the fences from
> > - * @excl: pointer for the exclusive fence
> > - * @list: pointer for the shared fence list
> > - *
> > - * Make sure we have a consisten exclusive fence and shared fence list.
> > - * Must be called with rcu read side lock held.
> > - */
> > -static inline void dma_resv_fences(struct dma_resv *obj,
> > - struct dma_fence **excl,
> > - struct dma_resv_list **list,
> > - u32 *shared_count)
> > -{
> > - do {
> > - *excl = rcu_dereference(obj->fence_excl);
> > - *list = rcu_dereference(obj->fence);
> > - *shared_count = *list ? (*list)->shared_count : 0;
> > - smp_rmb(); /* See dma_resv_add_excl_fence */
> > - } while (rcu_access_pointer(obj->fence_excl) != *excl);
> > -}
> > -
> > -/**
> > - * dma_resv_get_excl_rcu - get the reservation object's
> > - * exclusive fence, without lock held.
> > - * @obj: the reservation object
> > - *
> > - * If there is an exclusive fence, this atomically increments it's
> > - * reference count and returns it.
> > - *
> > - * RETURNS
> > - * The exclusive fence or NULL if none
> > - */
> > -static inline struct dma_fence *dma_resv_get_excl_rcu(struct dma_resv *obj)
> > -{
> > - struct dma_fence *fence;
> > -
> > - if (!rcu_access_pointer(obj->fence_excl))
> > - return NULL;
> > -
> > - rcu_read_lock();
> > - fence = dma_fence_get_rcu_safe(&obj->fence_excl);
> > - rcu_read_unlock();
> > -
> > - return fence;
> > -}
> > -
> > /**
> > * dma_resv_lock - lock the reservation object
> > * @obj: the reservation object
> > @@ -290,6 +228,51 @@ static inline void dma_resv_unlock(struct dma_resv *obj)
> > ww_mutex_unlock(&obj->lock);
> > }
> >
> > +/**
> > + * dma_resv_get_excl - get the reservation object's
> > + * exclusive fence, with update-side lock held
> > + * @obj: the reservation object
> > + *
> > + * Returns the exclusive fence (if any). Does NOT take a
> > + * reference. Writers must hold obj->lock, readers may only
> > + * hold a RCU read side lock.
> > + *
> > + * RETURNS
> > + * The exclusive fence or NULL
> > + */
> > +static inline struct dma_fence *
> > +dma_resv_get_excl(struct dma_resv *obj)
> > +{
> > + return rcu_dereference_protected(obj->fence_excl,
> > + dma_resv_held(obj));
> > +}
> > +
> > +/**
> > + * dma_resv_get_excl_rcu - get the reservation object's
> > + * exclusive fence, without lock held.
> > + * @obj: the reservation object
> > + *
> > + * If there is an exclusive fence, this atomically increments it's
> > + * reference count and returns it.
> > + *
> > + * RETURNS
> > + * The exclusive fence or NULL if none
> > + */
> > +static inline struct dma_fence *
> > +dma_resv_get_excl_rcu(struct dma_resv *obj)
> > +{
> > + struct dma_fence *fence;
> > +
> > + if (!rcu_access_pointer(obj->fence_excl))
> > + return NULL;
> > +
> > + rcu_read_lock();
> > + fence = dma_fence_get_rcu_safe(&obj->fence_excl);
> > + rcu_read_unlock();
> > +
> > + return fence;
> > +}
> > +
> > void dma_resv_init(struct dma_resv *obj);
> > void dma_resv_fini(struct dma_resv *obj);
> > int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences);
> > --
> > 2.23.0.rc1
> >
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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