It might happen if layout is flushed from outside the script task; window resizing/device rotation being what immediately comes to mind, as today in Servo those events go straight from compositor to layout without hitting the script task at all. (As an alternative design, we could route such events through the script task; this would remove the necessity of the mutex but would block layout for such events if script is running, even if the script hasn't touched the DOM.)
Patrick On August 28, 2014 7:05:09 PM PDT, Robert O'Callahan <rob...@ocallahan.org> wrote: >On Fri, Aug 29, 2014 at 12:56 PM, Cameron Zwarich <zwar...@mozilla.com> >wrote: > >> Is it strictly enforced that the script task never sees inconsistent >views >> of layout? This came up in the other thread about threading, but what >> prevents this incorrect scenario? >> >> 1) The script task takes the mutex to access one property of layout. >> 2) The script task releases the mutex. >> 3) Layout changes the property that was accessed. >> 4) The script task takes the mutex again to access the same property, >in >> the same turn of the event loop without modifying layout in any >intervening >> work since the last attempt. >> 5) The script task reads a different value from before. >> > >I'm confused. Before or during step 1, the layout must be brought up to >date (flushed, in Gecko parlance). So step 3 shouldn't happen since >layout >would already be fully up to date. > >Rob >-- >oIo otoeololo oyooouo otohoaoto oaonoyooonoeo owohooo oioso oaonogoroyo >owoiotoho oao oboroootohoeoro oooro osoiosotoeoro owoiololo oboeo >osouobojoeocoto otooo ojouodogomoeonoto.o oAogoaoiono,o oaonoyooonoeo >owohooo >osoaoyoso otooo oao oboroootohoeoro oooro osoiosotoeoro,o >o‘oRoaocoao,o’o >oioso >oaonosowoeoroaoboloeo otooo otohoeo ocooouoroto.o oAonodo oaonoyooonoeo >owohooo >osoaoyoso,o o‘oYooouo ofooooolo!o’o owoiololo oboeo oiono odoaonogoeoro >ooofo >otohoeo ofoioroeo ooofo ohoeololo. >_______________________________________________ >dev-servo mailing list >dev-servo@lists.mozilla.org >https://lists.mozilla.org/listinfo/dev-servo -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. _______________________________________________ dev-servo mailing list dev-servo@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-servo
