1765628 - Launching multiple background task instances simultaneously causes races in temp profile cleanup

Status: RESOLVED FIXED

(Toolkit :: Application Update, defect, P1)

Description

[Nick Alexander :nalexander [he/him]]

While investigating test failures re-enabling pingsender2, I discovered that launching many background task instances simultaneously causes races with the profile selection and the temp profile cleanup code.

I propose to salt the temporary profile directories with a pseudorandom value, so that it's very unlikely that two background task invocations will race to re-use the same temporary profile directory.

Salting in this manner will also make it a little harder to guess exactly where the temporary profile directory will be created, which is not crucial but may have some benefit as a defense-in-depth.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1722777

Comment 2

[Nick Alexander :nalexander [he/him]]

Attachment: Bug 1765628 - Test that launching many background tasks concurrently succeeds. r?nrishel

This verifies that stale temporary profile purging does not interfere
with concurrent temporary profile creation and locking.

Comment 3

[Nick Rishel [:nrishel]]

Attachment: Bug 1765628 - Don't delete recently created temporary profiles to avoid race between background task cleanup and background task profile locking. r=nalexander

Comment 4

[Nick Rishel [:nrishel]]

Attachment: Bug 1765628 - Pre: Account for endianness with PR_INT64_MAX and PR_INT64_MIN, also correct two's complement error for PR_INT64_MIN. r=nalexander

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/1002fb6d619e
Don't delete recently created temporary profiles to avoid race between background task cleanup and background task profile locking. r=nalexander
https://hg.mozilla.org/integration/autoland/rev/555b163d97e3
Test that launching many background tasks concurrently succeeds. r=nrishel

Comment 6

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/1002fb6d619e
https://hg.mozilla.org/mozilla-central/rev/555b163d97e3