[Mesa-dev] [PATCH v5] etnaviv: fix resource usage tracking across different pipe_context's

[Boris Brezillon]

On Thu, 21 Feb 2019 23:29:53 +0100
Boris Brezillon <boris.brezillon at collabora.com> wrote:

> Christian, Marek,
> 
> On Wed, 30 Jan 2019 05:28:14 +0100
> Marek Vasut <marex at denx.de> wrote:
> 
> > From: Christian Gmeiner <christian.gmeiner at gmail.com>
> > 
> > A pipe_resource can be shared by all the pipe_context's hanging off the
> > same pipe_screen.  
> 
> We seem to be impacted by the problem you're fixing here, but, while
> this patch definitely make things much better, the problem does not
> seem to be entirely fixed (at least in our case).
> 
> A bit more context: we have Qt App using QtWebEngine to render html
> content. When we call QtWebEngine::initialize(), which as for effect
> to allow shared GL contexts, we sometimes notice that part of the web
> page is mis-rendered. That does not happen when we omit the
> QtWebEngine::initialize() call.
> As said above, this patch make those rendering issues less likely to
> happen, but we still have the problem from time to time. So I thought
> I'd share my guesses about what could cause these issues before
> debugging it further.
> 
> First thing I noticed: I couldn't reproduce the problem with [1]
> applied (+ a tiny change forcing CPU-based tiling no matter the size of
> the region to tile/untile). So, my guess is that it's related to how we
> handle GPU-based tiling/untiling.
> Also noticed that we're testing the rsc->status here [2] without the
> screen->lock held, and there might be a race with another thread calling
> resource_used(). We might also lack a resource_read(ctx, &src->base)
> here [3]. But even after fixing those problems, the rendering issues
> are not gone.

I tested again with the following diff applied on top of your patch, and
the remaining rendering issues we had seem to be gone (don't know what I
messed up in my previous tests :-/).

--->8---
diff --git a/src/gallium/drivers/etnaviv/etnaviv_rs.c b/src/gallium/drivers/etnaviv/etnaviv_rs.c
index fc4f65dbeee1..b8c8b96a6f72 100644
--- a/src/gallium/drivers/etnaviv/etnaviv_rs.c
+++ b/src/gallium/drivers/etnaviv/etnaviv_rs.c
@@ -729,6 +729,7 @@ etna_try_rs_blit(struct pipe_context *pctx,
 
    etna_submit_rs_state(ctx, &copy_to_screen);
    resource_written(ctx, &dst->base);
+   resource_read(ctx, &src->base);
    dst->seqno++;
    dst->levels[blit_info->dst.level].ts_valid = false;
    ctx->dirty |= ETNA_DIRTY_DERIVE_TS;
diff --git a/src/gallium/drivers/etnaviv/etnaviv_transfer.c b/src/gallium/drivers/etnaviv/etnaviv_transfer.c
index a3013e624ead..e4b2ac605e63 100644
--- a/src/gallium/drivers/etnaviv/etnaviv_transfer.c
+++ b/src/gallium/drivers/etnaviv/etnaviv_transfer.c
@@ -356,6 +356,7 @@ etna_transfer_map(struct pipe_context *pctx, struct pipe_resource *prsc,
     * transfers without a temporary resource.
     */
    if (trans->rsc || !(usage & PIPE_TRANSFER_UNSYNCHRONIZED)) {
+      struct etna_screen *screen = ctx->screen;
       uint32_t prep_flags = 0;
 
       /*
@@ -364,11 +365,13 @@ etna_transfer_map(struct pipe_context *pctx, struct pipe_resource *prsc,
        * current GPU usage (reads must wait for GPU writes, writes must have
        * exclusive access to the buffer).
        */
+      mtx_lock(&screen->lock);
       if ((trans->rsc && (etna_resource(trans->rsc)->status & ETNA_PENDING_WRITE)) ||
           (!trans->rsc &&
            (((usage & PIPE_TRANSFER_READ) && (rsc->status & ETNA_PENDING_WRITE)) ||
            ((usage & PIPE_TRANSFER_WRITE) && rsc->status))))
          pctx->flush(pctx, NULL, 0);
+      mtx_unlock(&screen->lock);
 
       if (usage & PIPE_TRANSFER_READ)
          prep_flags |= DRM_ETNA_PREP_READ;