1265059 - Checking "don't show me this again" in the slow script dialog disables slow script protection forever

Status: RESOLVED WORKSFORME

(Firefox :: General, defect)

Description

[Jim Mathies [:jimm]]

Spin off from an e10s related discussion in bug 1264647 about this checkbox option.

The pref 'dom.max_script_run_time' controls whether the slow script dialog is displayed. If the value of this pref is set to 0, the slow script dialog is disabled. If the dialog is disabled, firefox will not attempt to recover from a long running script that janks the browser. [1][2]

Setting the pref to 0 is controlled by a innocuous checkbox in the slow script dialog. [3] The pref change is permanent for the profile.

This seems like a bug - turning off script jank protection should carry with it some sort of warning. Resetting the pref should probably be available through Preferences too. Alternatively the checkbox could apply only to the session or site vs. invoking a permanent change.

I wonder how many users mindlessly check this and forget it, and eventually run into problems with slow scripts hanging their browser.

[1] http://mxr.mozilla.org/mozilla-beta/source/modules/libpref/init/all.js#2549
[2] http://mxr.mozilla.org/mozilla-central/source/js/xpconnect/src/XPCJSRuntime.cpp#1395
[3] http://mxr.mozilla.org/mozilla-central/source/dom/base/nsGlobalWindow.cpp#10830
[4] http://mxr.mozilla.org/mozilla-central/source/js/xpconnect/src/XPCJSRuntime.cpp#1453

Comment 1

[Jim Mathies [:jimm]]

From our e10s beta experiment, here's data on beta users:

default (10): 452627,
0: 21129,
5: 1,
20: 49,
30: 10,
40: 8,
60: 1,
120: 1,
1000: 51,
1800: 80,
50000: 1

So around 4.6% of users have checked this checkbox and have no way to reset other than going into about:config. Also, due to bug 1264651, e10s now inherits this pref. I really think we should figure out some way to reset this on a regular basis.

Also, for reference this pref was added to telemetry env in bug 1265000.

Dolske can you help get this into the fx team's triage?

Comment 2

[:Gijs (he/him)]

We've turned the dialog off in the parent process, and the child process notification bar does not have a "don't ask me again" UI.