1395884 - Fix null TimeStamp compare MOZ_ASSERT failure in RequestContext::Notify

Status: RESOLVED FIXED

(Core :: Networking, defect)

Description

[Honza Bambas (:mayhemer)]

There is apparently a race between the time and low resolution now that can make mUntailAt timestamp be cleared just before the time is about to fire.

Comment 1

[Honza Bambas (:mayhemer)]

Attachment: v1

mUntailAt <= TimeStamp::NowLoRes() may eval to true just few milliseconds before the timer is scheduled to fire, but we don't cancel the timer.  In Notify() - when the timer fired - we than compare against null mUntailAt.  

Though, the condition is redundant, since mUntailAt is always exactly:
- non-null when we are inside the "keep tailed" interval
- null otherwise (after the timer has fired)

This is ensured by the code.  Hence, checking only if mUntailAt.IsNull() is enough to evaluate the condition correctly.

Comment 2

[Honza Bambas (:mayhemer)]

Credits for reporting and verifying the fix locally: Paul Adenot.  Thanks! :)

Comment 3

[Honza Bambas (:mayhemer)]

Attachment: v1.1

We can also remove the null TimeStamp() assignment (it's a no op).

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/b1f99cdeddec
Remove potential timer race and assertion in RequestContext tailing feature, r=dragana

Comment 5

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/b1f99cdeddec