1324814 - devtools leaks browser.xul window through _pingTelemetry, gDevTools, and TabTarget.onRemotenessChange

Status: RESOLVED INCOMPLETE

(DevTools :: General, defect, P2)

Description

[Ben Kelly [:bkelly, not reviewing]]

I got a leaked browser.xul in FF52 dev edition today.  The gc/gc logs suggest its some devtools or e10s code keeping stuff alive here:

bkelly@kosh /c/devel/tmp/cclogs/browserxul
$ /c/devel/heapgraph/find_roots.py cc-edges.1424.1482251995.log 0000019283FEE000
Parsing cc-edges.1424.1482251995.log. Done loading graph.

0000019286897060 [JS Object (Window)]
    --[UnwrapDOMObject(obj)]--> 0000019283FEE000 [nsGlobalWindow # 112 inner chrome://browser/conten
t/browser.xul]

    Root 0000019286897060 is a marked GC object.


bkelly@kosh /c/devel/tmp/cclogs/browserxul
$ /c/devel/heapgraph/find_roots.py gc-edges.1424.1482251995.log -bro 0000019286897060
Parsing gc-edges.1424.1482251995.log. Done loading graph.

via mCallback :
000001928CB312A0 [Proxy <no private>]
    --[private]--> 0000019280969F60 [Object <no private>]
    --[_pingTelemetry]--> 0000019282D84640 [Function exports.gDevToolsBrowser._pingTelemetry]
    --[fun_environment]--> 00000192845D6640 [LexicalEnvironment <no private>]
    --[gDevTools]--> 0000019280969A60 [Object <no private>]
    --[emit]--> 0000019282DBAD30 [Function bound emit]
    --[fun_environment]--> 0000019282DC8100 [Call <no private>]
    --[thisArg]--> 0000019280969C40 [Object <no private>]
    --[_eventEmitterListeners]--> 00000192FCE82070 [Map 00000192833FDD60]
    --[value]--> 000001928CBC13A0 [Array <no private>]
    --[objectElements[1]]--> 000001928D8419C0 [Function TabTarget.prototype.onRemotenessChange/on]
    --[fun_environment]--> 0000019293D93C80 [LexicalEnvironment <no private>]
    --[tab]--> 00000192FE8BE4E0 [Proxy <no private>]
    --[private]--> 000001928D031A00 [XULElement <no private>]
    --[group]--> 000001928685CEB0 [object_group]
    --[group_global]--> 0000019286897060 [Window <no private>]

Comment 1

[Alexandre Poirot [:ochameau]]

I imagine you have to open and close a top level window to have this leak?
Do you have a STR? I can't reproduce easily a leak to browser.xul.
I tried opening/closing a new browser window. Same but open the tools in the new window.
Same but open about:debugging in the new or the old window.

The report is really weird, especially about _pingTelemetry:
http://searchfox.org/mozilla-central/source/devtools/client/framework/devtools-browser.js#715-730
It does not seem to interact with browser references much.

Otherwise I looked at onRemotenessChange and haven't seen obvious error.
It could easily leak if some destruction codepath throw. So if you happen to reproduce it, it could be worth looking at the Browser Console and see if there is any actionable exception.

Comment 2

[Brian Grinstead [:bgrins]]

Marking ni? for Comment 1

Comment 3

[Ben Kelly [:bkelly, not reviewing]]

Sorry, I don't have steps to reproduce at the moment.  If I see it again I will try to narrow it down.

Comment 4

[Eric Rahm [:erahm]]

We're going to close this for now, Ben if you get STR please feel free to reopen.