1150691 - Cache Context close can race with storage invalidation

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Ben Kelly [:bkelly, not reviewing]]

While working on bug 1110485 I discovered that there is a way for QuotaManager to clear storage without the Cache Manager getting marked as invalid:

1) Manager calls Context::AllowToClose() because it thinks its idle.
2) Context is released and destroyed on background thread.
3) Context schedules a runnable to release OfflineStorage on main thread.
4) QM invalidates OfflineStorage on main thread.
5) OfflineStorage tries to invalidate Context, but its already gone.
6) OfflineStorage is desotryed when runnable from step (3) runs.

Also, the Manager is currently a bit sloppy in its determination of idle.  Right now it just checks for Listener objects, but it should also look at CacheId and BodyId references.

Comment 1

[Ben Kelly [:bkelly, not reviewing]]

Attachment: Fix Cache API race with storage invalidation. r=ehsan

https://treeherder.mozilla.org/#/jobs?repo=try&revision=04ee39679423

Comment 2

[Ben Kelly [:bkelly, not reviewing]]

I guess I should add a comment somewhere that you must do one of the following to keep your Manager reference valid:

 1) Add yourself as a listener by performing an op on the Manager
 2) Call AddRefCacheId
 3) Call AddRefBodyId

All current consumers do this, but it may not be obvious.

Alternatively, I could switch the "Manager is idle" check to a custom Release() method.  I don't really want to do that, though.

Comment 3

[(no longer active)]

Comment on attachment 8587649 [details] [diff] [review]
Fix Cache API race with storage invalidation. r=ehsan

Review of attachment 8587649 [details] [diff] [review]:
-----------------------------------------------------------------

It would be lovely if you can add comment 2 somewhere in the code.

Comment 4

[Ben Kelly [:bkelly, not reviewing]]

Landed with added comment:

remote:   https://hg.mozilla.org/integration/mozilla-inbound/rev/403400998055

Comment 5

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/403400998055