op 07-11-13 22:11, Rom Lemarchand schreef:

Hi Maarten, I tested your changes and needed the attached patch: behavior now seems equivalent as android sync. I haven't tested performance.

The issue resolved by this patch happens when i_b < b->num_fences and i_a >= a->num_fences (or vice versa). Then, pt_a is invalid and so dereferencing pt_a->context causes a crash.

Oops, thinko. :) Originally I had it correct by doing this:

+ /* + * Assume sync_fence a and b are both ordered and have no + * duplicates with the same context. + * + * If a sync_fence can only be created with sync_fence_merge + * and sync_fence_create, this is a reasonable assumption. + */ + for (i = i_a = i_b = 0; i_a < a->num_fences && i_b < b->num_fences; ) { + struct fence *pt_a = a->cbs[i_a].sync_pt; + struct fence *pt_b = b->cbs[i_b].sync_pt; + + if (pt_a->context < pt_b->context) { + sync_fence_add_pt(fence, &i, pt_a); + + i_a++; + } else if (pt_a->context > pt_b->context) { + sync_fence_add_pt(fence, &i, pt_b); + + i_b++; + } else { + if (pt_a->seqno - pt_b->seqno <= INT_MAX) + sync_fence_add_pt(fence, &i, pt_a); + else + sync_fence_add_pt(fence, &i, pt_b); + + i_a++; + i_b++; + } + } + + /* Add remaining fences from a or b*/ + for (; i_a < a->num_fences; i_a++) + sync_fence_add_pt(fence, &i, a->cbs[i_a].sync_pt); + + for (; i_b < b->num_fences; i_b++) + sync_fence_add_pt(fence, &i, b->cbs[i_b].sync_pt);

Then I thought I could clean it up by merging it, but that ended up being more unreadable and crashing... so I guess I'll revert back to this version. :)