dma-buf: add reservation_object_fences helper

Add a new helper to get a consistent set of pointers from the reservation
object. While at it group all access helpers together in the header file.

v2: correctly return shared_count as well

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/322378/?series=64837&rev=1

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index f45bfb29ef960346ae122dc94c067286fcf8c7de..67510f2be8bc3f2d9152a8b37b0d89f1b7534b27 100644 (file)
--- 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 reservation_object_list *fobj;
        struct dma_fence *fence_excl;
        __poll_t events;
-       unsigned shared_count, seq;
+       unsigned shared_count;
 
        dmabuf = file->private_data;
        if (!dmabuf || !dmabuf->resv)
@@ -213,21 +213,8 @@ 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();
-
-       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;
-       }
-
+       reservation_object_fences(resv, &fence_excl, &fobj, &shared_count);
        if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
                struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
                __poll_t pevents = EPOLLIN;
@@ -1157,7 +1144,6 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
        struct reservation_object *robj;
        struct reservation_object_list *fobj;
        struct dma_fence *fence;
-       unsigned seq;
        int count = 0, attach_count, shared_count, i;
        size_t size = 0;
 
@@ -1188,16 +1174,9 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
                                buf_obj->name ?: "");
 
                robj = buf_obj->resv;
-               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();
-               }
+               rcu_read_lock();
+               reservation_object_fences(robj, &fence, &fobj, &shared_count);
+               rcu_read_unlock();
 
                if (fence)
                        seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",

diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
index ad6775b32a73c24cde1df382ff3e473f3e7f5a2e..8fcaddffd5d47cf45b10c770eaf39a8a376fb4b1 100644 (file)
--- a/drivers/dma-buf/reservation.c
+++ b/drivers/dma-buf/reservation.c
@@ -317,17 +317,15 @@ int reservation_object_copy_fences(struct reservation_object *dst,
 {
        struct reservation_object_list *src_list, *dst_list;
        struct dma_fence *old, *new;
-       unsigned i;
+       unsigned int i, shared_count;
 
        reservation_object_assert_held(dst);
 
        rcu_read_lock();
-       src_list = rcu_dereference(src->fence);
 
 retry:
-       if (src_list) {
-               unsigned shared_count = src_list->shared_count;
-
+       reservation_object_fences(src, &new, &src_list, &shared_count);
+       if (shared_count) {
                rcu_read_unlock();
 
                dst_list = reservation_object_list_alloc(shared_count);
@@ -335,14 +333,14 @@ retry:
                        return -ENOMEM;
 
                rcu_read_lock();
-               src_list = rcu_dereference(src->fence);
-               if (!src_list || src_list->shared_count > shared_count) {
+               reservation_object_fences(src, &new, &src_list, &shared_count);
+               if (!src_list || shared_count > dst_list->shared_max) {
                        kfree(dst_list);
                        goto retry;
                }
 
                dst_list->shared_count = 0;
-               for (i = 0; i < src_list->shared_count; ++i) {
+               for (i = 0; i < shared_count; ++i) {
                        struct dma_fence *fence;
 
                        fence = rcu_dereference(src_list->shared[i]);
@@ -352,7 +350,6 @@ retry:
 
                        if (!dma_fence_get_rcu(fence)) {
                                reservation_object_list_free(dst_list);
-                               src_list = rcu_dereference(src->fence);
                                goto retry;
                        }
 
@@ -367,7 +364,10 @@ retry:
                dst_list = NULL;
        }
 
-       new = dma_fence_get_rcu_safe(&src->fence_excl);
+       if (new && !dma_fence_get_rcu(new)) {
+               reservation_object_list_free(dst_list);
+               goto retry;
+       }
        rcu_read_unlock();
 
        src_list = reservation_object_get_list(dst);
@@ -413,19 +413,18 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj,
 
        do {
                struct reservation_object_list *fobj;
-               unsigned int i, seq;
+               unsigned int i;
                size_t sz = 0;
 
-               shared_count = i = 0;
+               i = 0;
 
                rcu_read_lock();
-               seq = read_seqcount_begin(&obj->seq);
+               reservation_object_fences(obj, &fence_excl, &fobj,
+                                         &shared_count);
 
-               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;
 
@@ -453,7 +452,6 @@ int reservation_object_get_fences_rcu(struct reservation_object *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]))
@@ -461,7 +459,7 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj,
                        }
                }
 
-               if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
+               if (i != shared_count) {
                        while (i--)
                                dma_fence_put(shared[i]);
                        dma_fence_put(fence_excl);
@@ -505,18 +503,17 @@ long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
                                         bool wait_all, bool intr,
                                         unsigned long timeout)
 {
+       struct reservation_object_list *fobj;
        struct dma_fence *fence;
-       unsigned seq, shared_count;
+       unsigned shared_count;
        long ret = timeout ? timeout : 1;
        int i;
 
 retry:
-       shared_count = 0;
-       seq = read_seqcount_begin(&obj->seq);
        rcu_read_lock();
        i = -1;
 
-       fence = rcu_dereference(obj->fence_excl);
+       reservation_object_fences(obj, &fence, &fobj, &shared_count);
        if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
                if (!dma_fence_get_rcu(fence))
                        goto unlock_retry;
@@ -531,12 +528,6 @@ retry:
        }
 
        if (wait_all) {
-               struct reservation_object_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]);
 
@@ -559,11 +550,6 @@ retry:
 
        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))
@@ -608,24 +594,19 @@ reservation_object_test_signaled_single(struct dma_fence *passed_fence)
 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
                                          bool test_all)
 {
-       unsigned seq, shared_count;
+       struct reservation_object_list *fobj;
+       struct dma_fence *fence_excl;
+       unsigned shared_count;
        int ret;
 
        rcu_read_lock();
 retry:
        ret = true;
-       shared_count = 0;
-       seq = read_seqcount_begin(&obj->seq);
 
+       reservation_object_fences(obj, &fence_excl, &fobj, &shared_count);
        if (test_all) {
                unsigned i;
 
-               struct reservation_object_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]);
 
@@ -635,23 +616,12 @@ retry:
                        else if (!ret)
                                break;
                }
-
-               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 = reservation_object_test_signaled_single(
-                                                               fence_excl);
-                       if (ret < 0)
-                               goto retry;
-
-                       if (read_seqcount_retry(&obj->seq, seq))
-                               goto retry;
-               }
+       if (!shared_count && fence_excl) {
+               ret = reservation_object_test_signaled_single(fence_excl);
+               if (ret < 0)
+                       goto retry;
        }
 
        rcu_read_unlock();

diff --git a/include/linux/reservation.h b/include/linux/reservation.h
index 56b782fec49bf8d364ca00e36b6c5b52cf6641ca..c6c8c93785c40255e9eac271465c8ecb6c771f6c 100644 (file)
--- a/include/linux/reservation.h
+++ b/include/linux/reservation.h
@@ -81,6 +81,25 @@ struct reservation_object {
 #define reservation_object_assert_held(obj) \
        lockdep_assert_held(&(obj)->lock.base)
 
+/**
+ * reservation_object_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 *
+reservation_object_get_excl(struct reservation_object *obj)
+{
+       return rcu_dereference_protected(obj->fence_excl,
+                                        reservation_object_held(obj));
+}
+
 /**
  * reservation_object_get_list - get the reservation object's
  * shared fence list, with update-side lock held
@@ -96,6 +115,57 @@ reservation_object_get_list(struct reservation_object *obj)
                                         reservation_object_held(obj));
 }
 
+/**
+ * reservation_object_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
+reservation_object_fences(struct reservation_object *obj,
+                         struct dma_fence **excl,
+                         struct reservation_object_list **list,
+                         u32 *shared_count)
+{
+       unsigned int seq;
+
+       do {
+               seq = read_seqcount_begin(&obj->seq);
+               *excl = rcu_dereference(obj->fence_excl);
+               *list = rcu_dereference(obj->fence);
+               *shared_count = *list ? (*list)->shared_count : 0;
+       } while (read_seqcount_retry(&obj->seq, seq));
+}
+
+/**
+ * reservation_object_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 *
+reservation_object_get_excl_rcu(struct reservation_object *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;
+}
+
 /**
  * reservation_object_lock - lock the reservation object
  * @obj: the reservation object
@@ -239,51 +309,6 @@ reservation_object_unlock(struct reservation_object *obj)
        ww_mutex_unlock(&obj->lock);
 }
 
-/**
- * reservation_object_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 *
-reservation_object_get_excl(struct reservation_object *obj)
-{
-       return rcu_dereference_protected(obj->fence_excl,
-                                        reservation_object_held(obj));
-}
-
-/**
- * reservation_object_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 *
-reservation_object_get_excl_rcu(struct reservation_object *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 reservation_object_init(struct reservation_object *obj);
 void reservation_object_fini(struct reservation_object *obj);
 int reservation_object_reserve_shared(struct reservation_object *obj,