Re: [PATCH 2/6] dma-buf: Add dma_resv_get_singleton (v6)

Am 10.06.21 um 23:09 schrieb Jason Ekstrand:

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

v5 (Daniel Vetter):

• Rename from _rcu to _unlocked since it doesn't leak RCU details to the caller
• Fix docs
• Use ERR_PTR for error handling rather than an output dma_fence**

v5 (Jason Ekstrand):

• Drop the extra fence param and leave that to a separate patch

v6 (Jason Ekstrand):

• Rename to dma_resv_get_singleton to match the new naming convention for dma_resv helpers which work without taking a lock.

Signed-off-by: Jason Ekstrand jason@jlekstrand.net Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

Reviewed-by: Christian König christian.koenig@amd.com

Cc: Christian König christian.koenig@amd.com Cc: Maarten Lankhorst maarten.lankhorst@linux.intel.com

---

drivers/dma-buf/dma-resv.c | 91 ++++++++++++++++++++++++++++++++++++++ include/linux/dma-resv.h | 1 + 2 files changed, 92 insertions(+)

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index f26c71747d43a..1b26aa7e5d81c 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c @@ -34,6 +34,8 @@ */

#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> @@ -50,6 +52,10 @@

• write-side updates.

*/

+#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)
  

• DEFINE_WD_CLASS(reservation_ww_class); EXPORT_SYMBOL(reservation_ww_class);

@@ -495,6 +501,91 @@ int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **pfence_excl, } EXPORT_SYMBOL_GPL(dma_resv_get_fences);

+/**

• • dma_resv_get_singleton - get a single fence for the dma_resv object
• • @obj: the reservation object
• • 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
• • The singleton dma_fence on success or an ERR_PTR on failure
• */

+struct dma_fence *dma_resv_get_singleton(struct dma_resv *obj) +{

• struct dma_fence *result, **resv_fences, *fence, *chain, **fences;
• struct dma_fence_array *array;
• unsigned int num_resv_fences, num_fences;
• unsigned int err, i, j;
• err = dma_resv_get_fences(obj, NULL, &num_resv_fences, &resv_fences);
• if (err)

• return ERR_PTR(err);
  

• if (num_resv_fences == 0)

• return NULL;
  

• num_fences = 0;
• result = NULL;
• 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 (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 = ERR_PTR(-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 (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 = ERR_PTR(-ENOMEM);
  

• while (num_fences--)
  

• 	dma_fence_put(fences[num_fences]);
  

• kfree(fences);
  

• }

+put_resv_fences:

• while (num_resv_fences--)

• dma_fence_put(resv_fences[num_resv_fences]);
  

• kfree(resv_fences);
• return result;

+} +EXPORT_SYMBOL_GPL(dma_resv_get_singleton);

• /**
  • dma_resv_wait_timeout - 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 562b885cf9c3d..d60982975a786 100644 --- a/include/linux/dma-resv.h +++ b/include/linux/dma-resv.h @@ -275,6 +275,7 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence); int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **pfence_excl, unsigned *pshared_count, struct dma_fence ***pshared); int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src); +struct dma_fence *dma_resv_get_singleton(struct dma_resv *obj); long dma_resv_wait_timeout(struct dma_resv *obj, bool wait_all, bool intr, unsigned long timeout); bool dma_resv_test_signaled(struct dma_resv *obj, bool test_all);