[SyncFS] Add exclusive task support for TaskDependencyManager

[SyncFS] Add exclusive task support for TaskDependencyManager

BUG=344769
NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=260104

[tzik, 2014-03-27 05:25:44]

PTL.

We need to run some tasks as a exclusive task.
That means, no other background task runs parallel to a exclusive task.

[nhiroki, 2014-03-27 05:41:56]

On 2014/03/27 05:25:44, tzik wrote:
> PTL.
> 
> We need to run some tasks as a exclusive task.
> That means, no other background task runs parallel to a exclusive task.

Looks good to me. Just in case, can you tell me what kind of tasks should run
exclusively?

[tzik, 2014-03-27 06:29:25]

On 2014/03/27 05:41:56, nhiroki wrote:
> On 2014/03/27 05:25:44, tzik wrote:
> > PTL.
> > 
> > We need to run some tasks as a exclusive task.
> > That means, no other background task runs parallel to a exclusive task.
> 
> Looks good to me. Just in case, can you tell me what kind of tasks should run
> exclusively?

ListChangesTask should be exclusive for now.
Since its dependency is unpredictable until very last phase of its sequence,
 this needs to be exclusive to avoid race.

[nhiroki, 2014-03-27 13:10:49]

On 2014/03/27 06:29:25, tzik wrote:
> On 2014/03/27 05:41:56, nhiroki wrote:
> > On 2014/03/27 05:25:44, tzik wrote:
> > > PTL.
> > > 
> > > We need to run some tasks as a exclusive task.
> > > That means, no other background task runs parallel to a exclusive task.
> > 
> > Looks good to me. Just in case, can you tell me what kind of tasks should
run
> > exclusively?
> 
> ListChangesTask should be exclusive for now.
> Since its dependency is unpredictable until very last phase of its sequence,
>  this needs to be exclusive to avoid race.

I see, thanks! LGTM

[tzik, 2014-03-28 03:54:54]

The CQ bit was checked by tzik@chromium.org

[commit-bot: I haz the power, 2014-03-28 03:56:32]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tzik@chromium.org/212203003/1

[commit-bot: I haz the power, 2014-03-28 07:08:19]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-03-28 07:08:20]

Retried try job too often on ios_dbg_simulator for step(s) base_unittests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=ios_dbg_si...

[tzik, 2014-03-28 09:43:30]

The CQ bit was checked by tzik@chromium.org

[commit-bot: I haz the power, 2014-03-28 09:43:53]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tzik@chromium.org/212203003/1

[commit-bot: I haz the power, 2014-03-28 11:15:54]

Change committed as 260104