This should be possible now since we don't have the distinction between exclusive and shared fences any more.
The only possible pitfall is that a dma_fence would be reused during the RCU grace period, but even that could be handled with a single extra check.
Signed-off-by: Christian König christian.koenig@amd.com --- drivers/dma-buf/dma-resv.c | 33 ++++++++++++--------------------- drivers/dma-buf/st-dma-resv.c | 2 +- include/linux/dma-resv.h | 12 ------------ 3 files changed, 13 insertions(+), 34 deletions(-)
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index 5b64aa554c36..0cce6e4ec946 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c @@ -133,7 +133,6 @@ 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_ww_mutex_init(&obj->seq, &obj->lock);
RCU_INIT_POINTER(obj->fences, NULL); } @@ -292,28 +291,24 @@ void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence, fobj = dma_resv_fences_list(obj); count = fobj->num_fences;
- write_seqcount_begin(&obj->seq); - for (i = 0; i < count; ++i) { enum dma_resv_usage old_usage;
dma_resv_list_entry(fobj, i, obj, &old, &old_usage); if ((old->context == fence->context && old_usage >= usage) || - dma_fence_is_signaled(old)) - goto replace; + dma_fence_is_signaled(old)) { + dma_resv_list_set(fobj, i, fence, usage); + dma_fence_put(old); + return; + } }
BUG_ON(fobj->num_fences >= fobj->max_fences); - old = NULL; count++;
-replace: dma_resv_list_set(fobj, i, fence, usage); /* pointer update must be visible before we extend the num_fences */ smp_store_mb(fobj->num_fences, count); - - write_seqcount_end(&obj->seq); - dma_fence_put(old); } EXPORT_SYMBOL(dma_resv_add_fence);
@@ -341,7 +336,6 @@ void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context, dma_resv_assert_held(obj);
list = dma_resv_fences_list(obj); - write_seqcount_begin(&obj->seq); for (i = 0; list && i < list->num_fences; ++i) { struct dma_fence *old;
@@ -352,14 +346,12 @@ void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context, dma_resv_list_set(list, i, replacement, usage); dma_fence_put(old); } - write_seqcount_end(&obj->seq); } EXPORT_SYMBOL(dma_resv_replace_fences);
/* Restart the unlocked iteration by initializing the cursor object. */ static void dma_resv_iter_restart_unlocked(struct dma_resv_iter *cursor) { - cursor->seq = read_seqcount_begin(&cursor->obj->seq); cursor->index = 0; cursor->num_fences = 0; cursor->fences = dma_resv_fences_list(cursor->obj); @@ -388,8 +380,10 @@ static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor) cursor->obj, &cursor->fence, &cursor->fence_usage); cursor->fence = dma_fence_get_rcu(cursor->fence); - if (!cursor->fence) - break; + if (!cursor->fence) { + dma_resv_iter_restart_unlocked(cursor); + continue; + }
if (!dma_fence_is_signaled(cursor->fence) && cursor->usage >= cursor->fence_usage) @@ -415,7 +409,7 @@ struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor) do { dma_resv_iter_restart_unlocked(cursor); dma_resv_iter_walk_unlocked(cursor); - } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq)); + } while (dma_resv_fences_list(cursor->obj) != cursor->fences); rcu_read_unlock();
return cursor->fence; @@ -438,13 +432,13 @@ struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor)
rcu_read_lock(); cursor->is_restarted = false; - restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq); + restart = dma_resv_fences_list(cursor->obj) != cursor->fences; do { if (restart) dma_resv_iter_restart_unlocked(cursor); dma_resv_iter_walk_unlocked(cursor); restart = true; - } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq)); + } while (dma_resv_fences_list(cursor->obj) != cursor->fences); rcu_read_unlock();
return cursor->fence; @@ -540,10 +534,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src) } dma_resv_iter_end(&cursor);
- write_seqcount_begin(&dst->seq); list = rcu_replace_pointer(dst->fences, list, dma_resv_held(dst)); - write_seqcount_end(&dst->seq); - dma_resv_list_free(list); return 0; } diff --git a/drivers/dma-buf/st-dma-resv.c b/drivers/dma-buf/st-dma-resv.c index 8ace9e84c845..813779e3c9be 100644 --- a/drivers/dma-buf/st-dma-resv.c +++ b/drivers/dma-buf/st-dma-resv.c @@ -217,7 +217,7 @@ static int test_for_each_unlocked(void *arg) if (r == -ENOENT) { r = -EINVAL; /* That should trigger an restart */ - cursor.seq--; + cursor.fences = (void*)~0; } else if (r == -EINVAL) { r = 0; } diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h index 1db759eacc98..c8ccbc94d5d2 100644 --- a/include/linux/dma-resv.h +++ b/include/linux/dma-resv.h @@ -155,15 +155,6 @@ struct dma_resv { */ struct ww_mutex lock;
- /** - * @seq: - * - * Sequence count for managing RCU read-side synchronization, allows - * read-only access to @fences while ensuring we take a consistent - * snapshot. - */ - seqcount_ww_mutex_t seq; - /** * @fences: * @@ -202,9 +193,6 @@ struct dma_resv_iter { /** @fence_usage: the usage of the current fence */ enum dma_resv_usage fence_usage;
- /** @seq: sequence number to check for modifications */ - unsigned int seq; - /** @index: index into the shared fences */ unsigned int index;