In the Linux kernel, the following vulnerability has been resolved:

ACPI: processor idle: Mark LPI enter functions as cpuidle

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.