1485712 - SkTypeface memory leak in ScaledFonts with P-OMTP

Status: RESOLVED FIXED

(Core :: Graphics, defect, P1)

Description

[Lee Salzman [:lsalzman]]

Attachment: set SkTypeface atomically in ScaledFonts

There is a race condition in ScaledFont::GetSkTypeface when multiple threads try to call GetSkTypeface at the same time. This bug unfortunately affects all platforms, not just Linux.

To work around this, I have made mTypeface an atomic pointer, and we use a compare-and-swap with null to verify we're actually the first one initializing this pointer. In the event that a thread loses, it just derefs/deallocates the typeface and all is well.

This strategy is lock-free and will avoid any extra locks/blocking so we shouldn't see added overhead from it when we go to render text.

I've restructured the code a bit to move the details of the atomic initialization into ScaledFontBase, so that each ScaledFont implementation does not have to reproduce it.

Comment 1

[Ryan Hunt [:rhunt]]

Comment on attachment 9003502 [details] [diff] [review]
set SkTypeface atomically in ScaledFonts

Review of attachment 9003502 [details] [diff] [review]:
-----------------------------------------------------------------

Nice catch.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/582994eb6fa9
set SkTypeface atomically in ScaledFonts. r=rhunt

Comment 3

[Tiberius Oros[:tiberius_oros]]

https://hg.mozilla.org/mozilla-central/rev/582994eb6fa9