kernel/linux.git/drivers/acpi/processor_idle.c, branch v7.2-rc1

ACPI: processor_idle: Mark LPI enter functions as __cpuidle

2026-06-24T13:15:53+00:00

When function tracing or Kprobes is enabled, entering an ACPI Low Power Idle (LPI) state triggers the following RCU splat: RCU not on for: acpi_idle_lpi_enter+0x4/0xd8 WARNING: CPU: 8 PID: 0 at include/linux/trace_recursion.h:162 function_trace_call+0x1e8/0x228 The acpi_idle_lpi_enter() function is invoked within the cpuidle path after RCU has already been disabled for the current local CPU. Consequently, ftrace's function_trace_call() expects RCU to be actively watching before recording trace data, emitting a warning if it is not. Fix this by annotating acpi_idle_lpi_enter(), the generic __weak stub, and the RISC-V implementation of acpi_processor_ffh_lpi_enter() with __cpuidle. This moves these functions into the '.cpuidle.text' section, implicitly disabling ftrace instrumentation (notrace) along this sensitive path and preventing trace-induced RCU warnings during idle entry. Fixes: a36a7fecfe60 ("ACPI / processor_idle: Add support for Low Power Idle(LPI) states") Signed-off-by: Li RongQing Acked-by: lihuisong@huawei.com Link: https://patch.msgid.link/20260616072617.2272-1-lirongqing@baidu.com Signed-off-by: Rafael J. Wysocki

ACPI: processor: Add cpuidle driver check in acpi_processor_register_idle_driver()

2026-06-08T12:42:07+00:00

Commit 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle driver registration") moved the ACPI idle driver registration to acpi_processor_driver_init(), but it didn't check whether a cpuidle driver was already registered. For example, on Intel platforms, if the intel_idle driver is already loaded, the code would still evaluate the _CST object in the ACPI table and attempt to register the acpi_idle driver. This registration would fail with -EBUSY due to the existing check in cpuidle_register_driver. Add a check at the beginning of acpi_processor_register_idle_driver() to avoid unnecessary _CST evaluate and potential registration failures. Fixes: 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle driver registration") Signed-off-by: Tony W Wang-oc Link: https://patch.msgid.link/20260608190359.3254-1-TonyWWang-oc@zhaoxin.com Signed-off-by: Rafael J. Wysocki

ACPI: processor: idle: Reset cpuidle on C-state list changes

2026-04-07T13:32:20+00:00

When a power notification event occurs, existing ACPI idle states may become obsolete. The current implementation only performs a partial update, leaving critical cpuidle parameters, like target_residency_ns and exit_latency_ns, stale. Furthermore, per-CPU cpuidle_device data, including last_residency_ns, states_usage, and the disable flag, are not properly synchronized. Using these stale values leads to incorrect power management decisions. To ensure all parameters are correctly synchronized, modify the notification handling logic: 1. Unregister all cpuidle_device instances to ensure a clean slate. 2. Unregister and re-register the ACPI idle driver. This forces the framework to re-evaluate global state parameters and ensures the driver state matches the new hardware power profile. 3. Re-initialize power information and re-register cpuidle_device for all possible CPUs to restore functional idle management. This complete reset ensures that the cpuidle framework and the underlying ACPI states are perfectly synchronized after a power state change. Signed-off-by: Huisong Li [ rjw: Subject rewrite ] Link: https://patch.msgid.link/20260407081141.2493581-3-lihuisong@huawei.com Signed-off-by: Rafael J. Wysocki

ACPI: processor: idle: Fix NULL pointer dereference in hotplug path

2026-04-04T18:42:37+00:00

A cpuidle_device might fail to register during boot, but the system can continue to run. In such cases, acpi_processor_hotplug() can trigger a NULL pointer dereference when accessing the per-cpu acpi_cpuidle_device. So add NULL pointer check for the per-cpu acpi_cpuidle_device in acpi_processor_hotplug. Signed-off-by: Huisong Li Link: https://patch.msgid.link/20260403090253.998322-1-lihuisong@huawei.com Signed-off-by: Rafael J. Wysocki

ACPI: processor: idle: Reset power_setup_done flag on initialization failure

2026-04-04T18:41:01+00:00

The 'power_setup_done' flag is a key indicator used across the ACPI processor driver to determine if cpuidle are properly configured and available for a given CPU. Currently, this flag is set during the early stages of initialization. However, if the subsequent registration of the cpuidle driver in acpi_processor_register_idle_driver() or the per-CPU device registration in acpi_processor_power_init() fails, this flag remains set. This may lead to some issues where other functions in ACPI idle driver use these flags. Fix this by explicitly resetting this flag to 0 in these error paths. Signed-off-by: Huisong Li Link: https://patch.msgid.link/20260403085343.866440-1-lihuisong@huawei.com Signed-off-by: Rafael J. Wysocki

ACPI: processor: idle: Replace strlcat() with better alternative

2026-03-18T19:55:39+00:00

strlcpy() and strlcat() are confusing APIs and the former one already gone from the kernel. In preparation to kill strlcat() replace it with the better alternative. Signed-off-by: Andy Shevchenko Link: https://patch.msgid.link/20260317080218.1814693-1-andriy.shevchenko@linux.intel.com Signed-off-by: Rafael J. Wysocki

ACPI: processor: idle: Remove redundant static variable and rename cstate check function

2026-03-11T18:26:28+00:00

The function acpi_processor_cstate_first_run_checks() is currently called only once during initialization in acpi_processor_register_idle_driver(). Since its execution is already limited by the caller's lifecycle, the internal static 'first_run' variable is redundant and can be safely removed. Additionally, the current function name is no longer descriptive of its behavior, so rename the function to acpi_processor_update_max_cstate() to better reflect its actual purpose. Signed-off-by: Huisong Li Link: https://patch.msgid.link/20260311065038.4151558-4-lihuisong@huawei.com [ rjw: Changelog edits ] Signed-off-by: Rafael J. Wysocki

ACPI: processor: idle: Move max_cstate update out of the loop

2026-03-11T18:26:13+00:00

The acpi_processor_cstate_first_run_checks() function, which updates max_cstate on certain platforms, only needs to be executed once. Move this call outside of the loop to avoid redundant executions. Signed-off-by: Huisong Li Link: https://patch.msgid.link/20260311065038.4151558-3-lihuisong@huawei.com Signed-off-by: Rafael J. Wysocki

ACPI: processor: idle: Remove redundant cstate check in acpi_processor_power_init

2026-03-11T18:25:14+00:00

The function acpi_processor_cstate_first_run_checks() is responsible for updating max_cstate and performing initial hardware validation. Currently, this function is invoked within acpi_processor_power_init(). However, the initialization flow already ensures this is called during acpi_processor_register_idle_driver(). Therefore, the call in acpi_processor_power_init() is redundant and effectively performs no work, so remove it. Signed-off-by: Huisong Li Link: https://patch.msgid.link/20260311065038.4151558-2-lihuisong@huawei.com [ rjw: Changelog edits ] Signed-off-by: Rafael J. Wysocki

ACPI: processor: idle: Add missing bounds check in flatten_lpi_states()

2026-03-09T18:52:00+00:00

The inner loop in flatten_lpi_states() that combines composite LPI states can increment flat_state_cnt multiple times within the loop. The condition that guards this (checks bounds against ACPI_PROCESSOR _MAX_POWER) occurs at the top of the outer loop. flat_state_cnt might exceed ACPI_PROCESSOR_MAX_POWER if it is incremented multiple times within the inner loop between outer loop iterations. Add a bounds check after the increment inside the inner loop so that it breaks out when flat_state_cnt reaches ACPI_PROCESSOR_MAX_POWER. The existing check in the outer loop will then handle the warning. Signed-off-by: Jingkai Tan Reviewed-by: Sudeep Holla Link: https://patch.msgid.link/20260305213831.53985-1-contact@jingk.ai Signed-off-by: Rafael J. Wysocki