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. > --- > 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. > + > 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. > + * @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 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. > + 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 http://blog.ffwll.ch