| Re: [PATCH v3 2/2] decrement static keys on real destroy time [message #46133 is a reply to message #46132] |
Thu, 26 April 2012 22:13   |
Tejun Heo
Messages: 184
Registered: November 2006
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Senior Member |
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Hello, Glauber.
On Thu, Apr 26, 2012 at 06:58:37PM -0300, Glauber Costa wrote:
> At first I though that we could get rid of all this complication by
> calling stop machine from the static_branch API. This would all
> magically go away. I actually even tried it.
>
> However, reading the code for other architectures (other than x86),
> I found that they usually rely on the fixed instruction size to just
> patch an instruction atomically and go home happy.
>
> Using stop machine and the like would slow them down considerably.
> Not only slow down the static branch update (which is acceptable),
> but everybody else (which is horrible). It seemed to defeat the
> purpose of static branches a bit.
>
> The other users of static branches seems to be fine coping with the
> fact that in cases with multiple-sites, they will spread in time.
No, what I mean is that why can't you do about the same mutexed
activated inside static_key API function instead of requiring every
user to worry about the function returning asynchronously.
ie. synchronize inside static_key API instead of in the callers.
Thanks.
--
tejun
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