[PATCH][v2] ACPI: processor_idle: Mark LPI enter functions as __cpuidle

[lirongqing]

From: Li RongQing <lirongqing at baidu.com>

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 <lirongqing at baidu.com>
---
Diff with v1: add __cpuidle to acpi_processor_ffh_lpi_enter

 drivers/acpi/processor_idle.c | 4 ++--
 drivers/acpi/riscv/cpuidle.c  | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 390ab5f..4482cf2 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -1143,7 +1143,7 @@ static int acpi_processor_get_lpi_info(struct acpi_processor *pr)
 	return 0;
 }
 
-int __weak acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi)
+int __weak __cpuidle acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi)
 {
 	return -ENODEV;
 }
@@ -1156,7 +1156,7 @@ int __weak acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi)
  *
  * Return: 0 for success or negative value for error
  */
-static int acpi_idle_lpi_enter(struct cpuidle_device *dev,
+static int __cpuidle acpi_idle_lpi_enter(struct cpuidle_device *dev,
 			       struct cpuidle_driver *drv, int index)
 {
 	struct acpi_processor *pr;
diff --git a/drivers/acpi/riscv/cpuidle.c b/drivers/acpi/riscv/cpuidle.c
index 624f9bb..c76dbab 100644
--- a/drivers/acpi/riscv/cpuidle.c
+++ b/drivers/acpi/riscv/cpuidle.c
@@ -66,7 +66,7 @@ int acpi_processor_ffh_lpi_probe(unsigned int cpu)
 	return acpi_cpu_init_idle(cpu);
 }
 
-int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi)
+int __cpuidle acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi)
 {
 	u32 state = lpi->address;
 
-- 
2.9.4