Commit e5c9ffc6 authored by Aboorva Devarajan's avatar Aboorva Devarajan Committed by Rafael J. Wysocki
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cpuidle: Skip governor when only one idle state is available 



On certain platforms (PowerNV systems without a power-mgt DT node),
cpuidle may register only a single idle state. In cases where that
single state is a polling state (state 0), the ladder governor may
incorrectly treat state 1 as the first usable state and pass an
out-of-bounds index. This can lead to a NULL enter callback being
invoked, ultimately resulting in a system crash.

[   13.342636] cpuidle-powernv : Only Snooze is available
[   13.351854] Faulting instruction address: 0x00000000
[   13.376489] NIP [0000000000000000] 0x0
[   13.378351] LR  [c000000001e01974] cpuidle_enter_state+0x2c4/0x668

Fix this by adding a bail-out in cpuidle_select() that returns state 0
directly when state_count <= 1, bypassing the governor and keeping the
tick running.

Fixes: dc2251bf ("cpuidle: Eliminate the CPUIDLE_DRIVER_STATE_START symbol")
Signed-off-by: default avatarAboorva Devarajan <aboorvad@linux.ibm.com>
Reviewed-by: default avatarChristian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/20260216185005.1131593-2-aboorvad@linux.ibm.com


Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent c900e33e

drivers/cpuidle/cpuidle.c

+10 −0
Original line number Diff line number Diff line
@@ -359,6 +359,16 @@ noinstr int cpuidle_enter_state(struct cpuidle_device *dev, 
int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,

		   bool *stop_tick)

{

	/*

	 * If there is only a single idle state (or none), there is nothing

	 * meaningful for the governor to choose. Skip the governor and

	 * always use state 0 with the tick running.

	 */

	if (drv->state_count <= 1) {

		*stop_tick = false;

		return 0;

	}



	return cpuidle_curr_governor->select(drv, dev, stop_tick);

}