988421 - spdy pushed stream concurrency counting problem

Status: RESOLVED FIXED

(Core :: Networking: HTTP, defect)

Description

[Patrick McManus [:mcmanus]]

a spdy stream pushes up mConcurrent when it is activated, but before it actually gets a stream id. that's intentional - we don't want to start buffering from more requests than we can actually send out immediately and the id cannot be assigned until the syn-stream is sent because they must be monotonically increasing.

however a pulled stream that gets hooked up with a pushed cache hit never gets assigned a real stream id (because it never sends a syn-stream, it just uses the data from the pushed stream).

This lead to a leak in the mConcurrent semaphore. The fix is just to release the mConcurrent count when a push hit is made.

HTTP-2 is better here, in that all streams get cleaned up and we explicitly track whether or not they are counted against mConcurrent.. so there isn't a leak. However I added the release code to HTTP-2 as well because it allows the concurrency slot to be utilized for another pull stream earlier rather than waiting for the cleanup.

Comment 1

[Patrick McManus [:mcmanus]]

Attachment: spdy push concurrency mismatch

Comment 2

[Patrick McManus [:mcmanus]]

https://tbpl.mozilla.org/?tree=Try&rev=1ff999575698

Comment 3

[Patrick McManus [:mcmanus]]

remote:   https://hg.mozilla.org/integration/mozilla-inbound/rev/e04599ab2ee3

Comment 4

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

https://hg.mozilla.org/mozilla-central/rev/e04599ab2ee3