1193245 - Using Atomic in the suspend count of the media resource

Status: RESOLVED FIXED

(Core :: Audio/Video, defect)

Description

[Alastor Wu [:alwu]]

This bug is file from the bug1187092 comment34.
We need to use Atomic in the |mSuspendCount|.

Comment 1

[JW Wang [:jwwang] [:jw_wang]]

Please restate the problem so it is easier to understand what this bug tries to fix.

Comment 2

[Alastor Wu [:alwu]]

In present codebase, the |mSuspendCount| would be accessed in main thread and state machine thread, and we use the lock mechanism to avoid the race condition. 

However, we can use another more easier way to achieve it, that is using Atomic for the |mSuspendCount|.

Comment 3

[JW Wang [:jwwang] [:jw_wang]]

The problem is the lock is not always held when updating mSuspendCount which results in a data race. Since we are gonna move mSuspendCount into the suspend agent, and it is the only one member needing to be synchronized, we can just conveniently convert it to an Atomic to fix the data race.

Comment 4

[Alastor Wu [:alwu]]

Attachment: MozReview Request: Bug 1193245 - Using Atomic in the suspend count of the media resource.

Bug 1193245 - Using Atomic in the suspend count of the media resource.

In present codebase, the |mSuspendCount| would be accessed in main thread and state machine thread, and we use the lock mechanism to avoid the race condition.

However, we can use another more easier way to achieve it, that is using Atomic for the |mSuspendCount|.

Comment 5

[JW Wang [:jwwang] [:jw_wang]]

https://reviewboard.mozilla.org/r/15873/#review14111

Looks good to me.

Comment 6

[Alastor Wu [:alwu]]

Try-server result.
https://treeherder.mozilla.org/#/jobs?repo=try&revision=7e6ce8ff95e2

Comment 7

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/bbd394792e50

Comment 8

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

https://hg.mozilla.org/mozilla-central/rev/bbd394792e50

Comment 9

[Anthony Jones (:ajones, :kentuckyfriedtakahe, :k17e)]

JW - should we be using atomic?

Comment 10

[JW Wang [:jwwang] [:jw_wang]]

Per discussion on IRC and comment 3, we still prefer atomic over mutex for there is only one member to synchronize and atomic is more efficient and easier to use than mutex.