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freedreno/batch: fix dependency loop detection

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We can have a scenario like:

  A -> B
  A -> C -> B

When adding the A->C dependency, it doesn't really matter that C depends
on something that A depends on, that isn't a necessary condition for a
dependency loop.

Instead what we want to know is that nothing C depends on, directly or
indirectly, depends on A.  We can detect this by recursively OR'ing the
dependents_mask of C and all it's dependencies.

Signed-off-by: Rob Clark <robdclark@chromium.org>
This commit is contained in:
Rob Clark 2019-07-31 12:30:24 -07:00
parent e1790c532a
commit 9d5beab441
1 changed files with 10 additions and 11 deletions
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21
src/gallium/drivers/freedreno/freedreno_batch.c
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@ -401,31 +401,30 @@ fd_batch_flush(struct fd_batch *batch, bool sync)
fd_batch_reference(&tmp, NULL);
}
/* does 'batch' depend directly or indirectly on 'other' ? */
static bool
batch_depends_on(struct fd_batch *batch, struct fd_batch *other)
/* find a batches dependents mask, including recursive dependencies: */
static uint32_t
recursive_dependents_mask(struct fd_batch *batch)
{
struct fd_batch_cache *cache = &batch->ctx->screen->batch_cache;
struct fd_batch *dep;
uint32_t dependents_mask = batch->dependents_mask;
if (batch->dependents_mask & (1 << other->idx))
return true;
foreach_batch(dep, cache, batch->dependents_mask)
dependents_mask |= recursive_dependents_mask(dep);
foreach_batch(dep, cache, other->dependents_mask)
if (batch_depends_on(batch, dep))
return true;
return false;
return dependents_mask;
}
void
fd_batch_add_dep(struct fd_batch *batch, struct fd_batch *dep)
{
pipe_mutex_assert_locked(batch->ctx->screen->lock);
if (batch->dependents_mask & (1 << dep->idx))
return;
/* a loop should not be possible */
debug_assert(!batch_depends_on(dep, batch));
debug_assert(!((1 << batch->idx) & recursive_dependents_mask(dep)));
struct fd_batch *other = NULL;
fd_batch_reference_locked(&other, dep);