1346062 - stylo: bogus entries in the style sharing cache

Status: RESOLVED INVALID

(Core :: CSS Parsing and Computation, defect, P1)

Description

[Bobby Holley (:bholley)]

See https://github.com/servo/servo/pull/15891#issuecomment-285542560

Just getting this on file since it's more serious than the PR it was discovered in.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Just to summarize the discussion on IRC:

 * The failures are subpixel failures, and there's a single rule in the page that reads |body > span { border: 3px solid blue; }|, so it seems at least a bit more dubious that they're styling-related.
 * The DOM in that page is really small, which probably makes the sequential traversal come in. The style sharing cache currently barely works for that case (bug 1332525).
 * Cannot repro locally.
 * Xidorn found a very similar reftest failure when accidentally disabling all style sharing. This is probably related.

Thus, I believe the diagnostic may be a bit different. Tomorrow I'll debug it if they don't end up being Servo intermittents.

Comment 2

[Emilio Cobos Álvarez (:emilio)]

This is a servo layout bug, read from http://logs.glob.uno/?c=mozilla%23servo&s=10+Mar+2017&e=10+Mar+2017#c628410.

We're not inserting twice as I thought in the first time. This happens to manifest itself because we share with a different pattern with my patch, and we wipe the cache on different circumstances as an optimization for parallel traversal.

The permalink to the exact line causing the failure is https://github.com/servo/servo/blob/336aa795b4b9933436c9df0200de64e18b6f3b7e/components/layout/inline.rs#L1771. I'm not sure what's the intention of that line of code tbh.

Comment 3

[Bobby Holley (:bholley)]

Man, crazy bug - glad it wasn't in the style system though. Thanks for tracking it down emilio!