916454 - Browser hanging when reloading some pages while the debugger is open and source maps are enabled

Status: RESOLVED FIXED

(DevTools :: Debugger, defect, P2)

Description

[Victor Porof [:vporof][:vp]]

Attachment: log.txt

STR:

1. Go to http://todomvc.com/
2. Open debugger, wait for sources to be shown
3. Refresh

It takes around 20 seconds for the sources to finish fetching. The browser freezes in the meantime.

Comment 1

[Victor Porof [:vporof][:vp]]

Refreshing is instant if I disable source maps via the gear menu. Nick?

Comment 2

[Panos Astithas (he/him) [:past] (please ni?)]

Backing out bug 914930 and bug 762761 doesn't fix this FWIW.

Comment 3

[Nick Fitzgerald [:fitzgen] [⏰PST; UTC-8]]

I can reproduce, and verify that when source maps aren't enabled it doesn't happen. Will look into this.

Comment 4

[Nick Fitzgerald [:fitzgen] [⏰PST; UTC-8]]

I tried to upload a profile, but it is too big for bugzilla to accept it.

The culprit is parsing the mappings, which I think we can lazily delay until we actually query for a source mapped location. However, that will still cause a hang, just later on down the line.

Might need to change the SourceMapConsumer interface, let more stuff be async and put parsing in a yielding loop.

Comment 5

[Nick Fitzgerald [:fitzgen] [⏰PST; UTC-8]]

Attachment: bug-916454-source-maps-reload-hang.patch

This patch delays the parsing of a source map's mappings until queried for a source location.

Comment 6

[Nick Fitzgerald [:fitzgen] [⏰PST; UTC-8]]

Associate PR: https://github.com/mozilla/source-map/pull/81

Comment 7

[Panos Astithas (he/him) [:past] (please ni?)]

Comment on attachment 812360 [details] [diff] [review]
bug-916454-source-maps-reload-hang.patch

Review of attachment 812360 [details] [diff] [review]:
-----------------------------------------------------------------

I have to say Nightly no longer seems to hang with the STR in comment 0, so I'm guessing something else must have fixed this, but the change in the patch seems reasonable and works fine in my testing.

Comment 8

[Panos Astithas (he/him) [:past] (please ni?)]

Scratch that, I forgot that my main browser on Linux is the stable version of Firefox. The bug is still there on Nightly without this patch.

Comment 9

[Nick Fitzgerald [:fitzgen] [⏰PST; UTC-8]]

https://hg.mozilla.org/integration/fx-team/rev/1f6acfcba58f

Comment 10

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/1f6acfcba58f