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When the target residency of the current candidate idle state is
greater than the expected time till the closest timer (the sleep
length), it does not matter whether or not the tick has already been
stopped or if it is going to be stopped. The closest timer will
trigger anyway at its due time, so if an idle state with target
residency above the sleep length is selected, energy will be wasted
and there may be excess latency.
Of course, if the closest timer were canceled before it could trigger,
a deeper idle state would be more suitable, but this is not expected
to happen (generally speaking, hrtimers are not expected to be
canceled as a rule).
Accordingly, the teo_state_ok() check done in that case causes energy to
be wasted more often than it allows any energy to be saved (if it allows
any energy to be saved at all), so drop it and let the governor use the
teo_find_shallower_state() return value as the new candidate idle state
index.
Fixes: 21d28cd2fa ("cpuidle: teo: Do not call tick_nohz_get_sleep_length() upfront")
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Tested-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/5955081.DvuYhMxLoT@rafael.j.wysocki
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.