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[v1,0/5] cpuidle: Take possible negative "sleep length" values into account

Message ID 2764850.e9J7NaK4W3@kreacher (mailing list archive)
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Series cpuidle: Take possible negative "sleep length" values into account | expand

Message

Rafael J. Wysocki March 29, 2021, 6:12 p.m. UTC 
Hi All,

As follows from the discussion triggered by the patch at

https://lore.kernel.org/lkml/20210311123708.23501-2-frederic@kernel.org/

the cpuidle governors using tick_nohz_get_sleep_length() assume it to always
return positive values which is not correct in general.

To address this issues, first document the fact that negative values can
be returned by tick_nohz_get_sleep_length() (patch [1/5]).  Then, in
preparation for more substantial changes, change the data type of two
fields in struct cpuidle_state to s64 so they can be used in computations
involving negative numbers safely (patch [2/5]).

Next, adjust the teo governor a bit so that negative "sleep length" values
are counted like zero by it (patch [3/5]) and modify it so as to avoid
mishandling negative "sleep length" values (patch [4/5]).

Finally, make the menu governor take negative "sleep length" values into
account properly (patch [5/5]).

Please see the changelogs of the patches for details.

Thanks!

Comments

Rafael J. Wysocki April 7, 2021, 5:24 p.m. UTC | #1 
On Mon, Mar 29, 2021 at 8:38 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
>
> Hi All,
>
> As follows from the discussion triggered by the patch at
>
> https://lore.kernel.org/lkml/20210311123708.23501-2-frederic@kernel.org/
>
> the cpuidle governors using tick_nohz_get_sleep_length() assume it to always
> return positive values which is not correct in general.
>
> To address this issues, first document the fact that negative values can
> be returned by tick_nohz_get_sleep_length() (patch [1/5]).  Then, in
> preparation for more substantial changes, change the data type of two
> fields in struct cpuidle_state to s64 so they can be used in computations
> involving negative numbers safely (patch [2/5]).
>
> Next, adjust the teo governor a bit so that negative "sleep length" values
> are counted like zero by it (patch [3/5]) and modify it so as to avoid
> mishandling negative "sleep length" values (patch [4/5]).
>
> Finally, make the menu governor take negative "sleep length" values into
> account properly (patch [5/5]).
>
> Please see the changelogs of the patches for details.

Given no objections or concerns regarding this lot, let me queue it up.

Thanks!