Re: [tip:locking/core] rwsem: Add comments to explain the meaning of the rwsem's count field

From: Davidlohr Bueso
Date: Wed May 14 2014 - 10:27:18 EST


On Mon, 2014-05-05 at 01:46 -0700, tip-bot for Tim Chen wrote:
> Commit-ID: 3cf2f34e1a3d4d5ff209d087925cf950e52f4805
> Gitweb: http://git.kernel.org/tip/3cf2f34e1a3d4d5ff209d087925cf950e52f4805
> Author: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> AuthorDate: Fri, 2 May 2014 12:53:57 -0700
> Committer: Ingo Molnar <mingo@xxxxxxxxxx>
> CommitDate: Sun, 4 May 2014 20:34:26 +0200
>
> rwsem: Add comments to explain the meaning of the rwsem's count field
>
> It took me quite a while to understand how rwsem's count field
> mainifested itself in different scenarios.
>
> Add comments to provide a quick reference to the the rwsem's count
> field for each scenario where readers and writers are contending
> for the lock.
>
> Hopefully it will be useful for future maintenance of the code and
> for people to get up to speed on how the logic in the code works.

sigh, after this commit, the opt spin patch no longer applies, I'm
rebasing and send out v5.

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