1700676 - Updating if an origin is accessed on the in-memory object is not guaranteed to be done before shutting down storage

Status: RESOLVED FIXED

(Core :: Storage: Quota Manager, defect, P2)

Description

[Tom Tung [:tt, :ttung]]

I found this while running originInit.js with my patches in the verify mode (more accurately in the chaos mode).

The test cases basically create a normal cache origin and then check files in the testing cache directory.
In short, the steps roughly are:

1. Running a script with some normal cache operations.
2. Resetting.
3. Checking files.
4. Initializing.
5. Checking files again.

In step 4, I expected that the testing origin should be initialized (In other words, InitOrigin should be called).

However, actually, in some extreme cases, that InitOrigin wasn't called and thus some test cases fail because of that.

After looking into it, I think what happened was:
a. In step 1, on the Background thread, Cache registers a directory lock.
b. In step 2, on the Background thread, the Reset operation registers a directory lock and it waits for the blocking lock in step 1 to be released.
c. In steps 2, after the lock is destructed, on the IO thread, the Reset operation shuts down the storage and then writes whether the origin is accessed into database.
d. In steps 2, on the Background thread, the access time and if the origin has been accessed are updated when unregistering the directory lock.
e. In step 4, on the Background thread, it only initializes the origins that are marked as accessed.

In general case, the sequence is like: a->b->d>c->e.
However, it's possible to be like: a->b->c->d->e. It's possible that the origin isn't marked as accessed on the Background thread before shutting down the storage on the IO thread.

For the fix, I think we should unregister the lock before unlocks other blocked locks. So that whether an origin is accessed is updated before updating the SQL statement.

Comment 1

[Tom Tung [:tt, :ttung]]

Attachment: Bug 1700676 - Unregister the lock itself before unblock other locks;

Depends on D109639

Comment 2

[Tom Tung [:tt, :ttung]]

try: https://treeherder.mozilla.org/#/jobs?repo=try&revision=91ae72a061d0f1482532f310f8a0983a515735b4

Comment 3

[Tom Tung [:tt, :ttung]]

Last full try push: https://treeherder.mozilla.org/#/jobs?repo=try&revision=c04f614e2fd4b2701e8207c92d523b324ae0343e

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/10f3e7d643a7
Unregister the lock itself before unblock other locks; r=dom-storage-reviewers,sg,janv

Comment 5

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/10f3e7d643a7