]> git.ipfire.org Git - thirdparty/kernel/stable.git/commit
cpuidle: governors: menu: Avoid using invalid recent intervals data
authorRafael J. Wysocki <rafael.j.wysocki@intel.com>
Mon, 11 Aug 2025 15:03:11 +0000 (17:03 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 20 Aug 2025 16:40:51 +0000 (18:40 +0200)
commitd3022be0989ba4ed66a8c6576eed19db48f59599
tree9002818fe0685957d7fd489706957376823c8a3e
parent18559709889f00b4b022d71464e57e675bb3d7d7
cpuidle: governors: menu: Avoid using invalid recent intervals data

[ Upstream commit fa3fa55de0d6177fdcaf6fc254f13cc8f33c3eed ]

Marc has reported that commit 85975daeaa4d ("cpuidle: menu: Avoid
discarding useful information") caused the number of wakeup interrupts
to increase on an idle system [1], which was not expected to happen
after merely allowing shallower idle states to be selected by the
governor in some cases.

However, on the system in question, all of the idle states deeper than
WFI are rejected by the driver due to a firmware issue [2].  This causes
the governor to only consider the recent interval duriation data
corresponding to attempts to enter WFI that are successful and the
recent invervals table is filled with values lower than the scheduler
tick period.  Consequently, the governor predicts an idle duration
below the scheduler tick period length and avoids stopping the tick
more often which leads to the observed symptom.

Address it by modifying the governor to update the recent intervals
table also when entering the previously selected idle state fails, so
it knows that the short idle intervals might have been the minority
had the selected idle states been actually entered every time.

Fixes: 85975daeaa4d ("cpuidle: menu: Avoid discarding useful information")
Link: https://lore.kernel.org/linux-pm/86o6sv6n94.wl-maz@kernel.org/
Link: https://lore.kernel.org/linux-pm/7ffcb716-9a1b-48c2-aaa4-469d0df7c792@arm.com/
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Christian Loehle <christian.loehle@arm.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/2793874.mvXUDI8C0e@rafael.j.wysocki
Signed-off-by: Sasha Levin <sashal@kernel.org>
drivers/cpuidle/governors/menu.c