Am 25.05.21 um 14:38 schrieb Daniel Vetter:
On Mon, May 24, 2021 at 03:04:35PM -0500, Jason Ekstrand wrote:
On Fri, May 21, 2021 at 12:48 PM Daniel Vetter <daniel@xxxxxxxx> wrote:
On Thu, May 20, 2021 at 02:00:05PM -0500, Jason Ekstrand wrote:
Add a helper function to get a single fence representing
all fences in a dma_resv object.
This fence is either the only one in the object or all not
signaled fences of the object in a flatted out dma_fence_array.
v2 (Jason Ekstrand):
- Take reference of fences both for creating the dma_fence_array and in
the case where we return one fence.
- Handle the case where dma_resv_get_list() returns NULL
v3 (Jason Ekstrand):
- Add an _rcu suffix because it is read-only
- Rewrite to use dma_resv_get_fences_rcu so it's RCU-safe
- Add an EXPORT_SYMBOL_GPL declaration
- Re-author the patch to Jason since very little is left of Christian
König's original patch
- Remove the extra fence argument
v4 (Jason Ekstrand):
- Restore the extra fence argument
Signed-off-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
get_singleton
Spurious thing here.
Fixed.
---
drivers/dma-buf/dma-resv.c | 122 +++++++++++++++++++++++++++++++++++++
include/linux/dma-resv.h | 3 +
2 files changed, 125 insertions(+)
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 6ddbeb5dfbf65..25995fc15c370 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -33,6 +33,8 @@
*/
#include <linux/dma-resv.h>
+#include <linux/dma-fence-chain.h>
+#include <linux/dma-fence-array.h>
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/sched/mm.h>
@@ -49,6 +51,19 @@
* write-side updates.
*/
+/**
+ * dma_fence_deep_dive_for_each - deep dive into the fence containers
+ * @fence: resulting fence
+ * @chain: variable for a dma_fence_chain
+ * @index: index into a dma_fence_array
+ * @head: starting point
+ *
+ * Helper to deep dive into the fence containers for flattening them.
+ */
+#define dma_fence_deep_dive_for_each(fence, chain, index, head) \
+ dma_fence_chain_for_each(chain, head) \
+ dma_fence_array_for_each(fence, index, chain)
Since this is is just internal helper in the .c file we generally don't
document it. Maybe small comment if you feel it's worth it.
Sure, I can write LESS documentation. :-P
+
DEFINE_WD_CLASS(reservation_ww_class);
EXPORT_SYMBOL(reservation_ww_class);
@@ -517,6 +532,113 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
}
EXPORT_SYMBOL_GPL(dma_resv_get_fences_rcu);
+/**
+ * dma_resv_get_singleton - get a single fence for the dma_resv object
Name doesn't match here.
Fixed.
+ * @obj: the reservation object
+ * @extra: extra fence to add to the resulting array
+ * @result: resulting dma_fence
+ *
+ * Get a single fence representing all unsignaled fences in the dma_resv object
+ * plus the given extra fence. If we got only one fence return a new
+ * reference to that, otherwise return a dma_fence_array object.
+ *
+ * RETURNS
+ * Returns -NOMEM if allocations fail, zero otherwise.
Kernel often encodes this in ERR_PTR so that you don't have to pass a
pointer to store the result. Would feel more kerenl-y I think that way. So
no result parameter, and on alloc failure you'd return
Done.
return ERR_PTR(-ENOMEM);
+ */
+int dma_resv_get_singleton_rcu(struct dma_resv *obj, struct dma_fence *extra,
tbh the _rcu here is confusing. I think _unlocked is the better suffix,
maybe we should rename dma_resv_get_fences_rcu too for consistency. The
rcu-ness of the lookup isn't leaked to callers at all, so no point giving
them a panic.
I can make that change. I'll also include a patch in the next re-send
that renames all the _rcu helpers to _unlocked for consistency.
Maybe double-check with Christian König whether he's on board with this
bikeshed, but the current _rcu postfix we have in some dma_resv functions
really confuses me.
Well I would say yes please :)
The _rcu postfix was something I was always wondering about as well.
Christian.
-Daniel
--Jason
+ struct dma_fence **result)
+{
+ struct dma_fence **resv_fences, *fence, *chain, **fences;
+ struct dma_fence_array *array;
+ unsigned int num_resv_fences, num_fences;
+ unsigned int ret, i, j;
+
+ ret = dma_resv_get_fences_rcu(obj, NULL, &num_resv_fences, &resv_fences);
+ if (ret)
+ return ret;
+
+ num_fences = 0;
+ *result = NULL;
+
+ if (num_resv_fences == 0 && !extra)
+ return 0;
+
+ for (i = 0; i < num_resv_fences; ++i) {
+ dma_fence_deep_dive_for_each(fence, chain, j, resv_fences[i]) {
+ if (dma_fence_is_signaled(fence))
+ continue;
+
+ *result = fence;
+ ++num_fences;
+ }
+ }
+
+ if (extra) {
+ dma_fence_deep_dive_for_each(fence, chain, j, extra) {
+ if (dma_fence_is_signaled(fence))
+ continue;
+
+ *result = fence;
+ ++num_fences;
+ }
+ }
+
+ if (num_fences <= 1) {
+ *result = dma_fence_get(*result);
+ goto put_resv_fences;
+ }
+
+ fences = kmalloc_array(num_fences, sizeof(struct dma_fence*),
+ GFP_KERNEL);
+ if (!fences) {
+ *result = NULL;
+ ret = -ENOMEM;
+ goto put_resv_fences;
+ }
+
+ num_fences = 0;
+ for (i = 0; i < num_resv_fences; ++i) {
+ dma_fence_deep_dive_for_each(fence, chain, j, resv_fences[i]) {
+ if (!dma_fence_is_signaled(fence))
+ fences[num_fences++] = dma_fence_get(fence);
+ }
+ }
+
+ if (extra) {
+ dma_fence_deep_dive_for_each(fence, chain, j, extra) {
+ if (dma_fence_is_signaled(fence))
+ fences[num_fences++] = dma_fence_get(fence);
+ }
+ }
+
+ if (num_fences <= 1) {
+ *result = num_fences ? fences[0] : NULL;
+ kfree(fences);
+ goto put_resv_fences;
+ }
+
+ array = dma_fence_array_create(num_fences, fences,
+ dma_fence_context_alloc(1),
+ 1, false);
+ if (array) {
+ *result = &array->base;
+ } else {
+ *result = NULL;
+ while (num_fences--)
+ dma_fence_put(fences[num_fences]);
+ kfree(fences);
+ ret = -ENOMEM;
+ }
+
+put_resv_fences:
+ while (num_resv_fences--)
+ dma_fence_put(resv_fences[num_resv_fences]);
+ kfree(resv_fences);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dma_resv_get_singleton_rcu);
With the nits addressed:
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
+
/**
* dma_resv_wait_timeout_rcu - Wait on reservation's objects
* shared and/or exclusive fences.
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
index d44a77e8a7e34..d49ca263e78b4 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h
@@ -285,6 +285,9 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src);
+int dma_resv_get_singleton_rcu(struct dma_resv *obj, struct dma_fence *extra,
+ struct dma_fence **result);
+
long dma_resv_wait_timeout_rcu(struct dma_resv *obj, bool wait_all, bool intr,
unsigned long timeout);
--
2.31.1
--
Daniel Vetter
Software Engineer, Intel Corporation
https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&data=04%7C01%7Cchristian.koenig%40amd.com%7C4bfa8c05efd842e47f3b08d91f7a0121%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637575431134167291%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=8y%2BHz5GldUZK6Ey%2FuZUQUMg%2BObKticrSVX2gx3NBDOw%3D&reserved=0
