diff mbox series

[v9,2/7] arm64: idle: Tag the arm64 idle functions as __cpuidle

Message ID 20230601143109.v9.2.I4baba13e220bdd24d11400c67f137c35f07f82c7@changeid
State New
Headers
Series arm64: Add debug IPI for backtraces / kgdb; try to use NMI for it |

Commit Message

Doug Anderson June 1, 2023, 9:31 p.m. UTC 
  As per the (somewhat recent) comment before the definition of
`__cpuidle`, the tag is like `noinstr` but also marks a function so it
can be identified by cpu_in_idle(). Let'a add this.

After doing this then when we dump stack traces of all processors
using nmi_cpu_backtrace() then instead of getting useless backtraces
we get things like:

  NMI backtrace for cpu N skipped: idling at cpu_do_idle+0x94/0x98

NOTE: this patch won't make cpu_in_idle() work perfectly for arm64,
but it doesn't hurt and does catch some cases. Specifically an example
that wasn't caught in my testing looked like this:

 gic_cpu_sys_reg_init+0x1f8/0x314
 gic_cpu_pm_notifier+0x40/0x78
 raw_notifier_call_chain+0x5c/0x134
 cpu_pm_notify+0x38/0x64
 cpu_pm_exit+0x20/0x2c
 psci_enter_idle_state+0x48/0x70
 cpuidle_enter_state+0xb8/0x260
 cpuidle_enter+0x44/0x5c
 do_idle+0x188/0x30c

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v9:
- Added to commit message that this doesn't catch all cases.

Changes in v8:
- "Tag the arm64 idle functions as __cpuidle" new for v8

 arch/arm64/kernel/idle.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Mark Rutland Aug. 7, 2023, 9:52 a.m. UTC | #1 
On Thu, Jun 01, 2023 at 02:31:46PM -0700, Douglas Anderson wrote:
> As per the (somewhat recent) comment before the definition of
> `__cpuidle`, the tag is like `noinstr` but also marks a function so it
> can be identified by cpu_in_idle(). Let'a add this.
> 
> After doing this then when we dump stack traces of all processors
> using nmi_cpu_backtrace() then instead of getting useless backtraces
> we get things like:
> 
>   NMI backtrace for cpu N skipped: idling at cpu_do_idle+0x94/0x98
> 
> NOTE: this patch won't make cpu_in_idle() work perfectly for arm64,
> but it doesn't hurt and does catch some cases. Specifically an example
> that wasn't caught in my testing looked like this:
> 
>  gic_cpu_sys_reg_init+0x1f8/0x314
>  gic_cpu_pm_notifier+0x40/0x78
>  raw_notifier_call_chain+0x5c/0x134
>  cpu_pm_notify+0x38/0x64
>  cpu_pm_exit+0x20/0x2c
>  psci_enter_idle_state+0x48/0x70
>  cpuidle_enter_state+0xb8/0x260
>  cpuidle_enter+0x44/0x5c
>  do_idle+0x188/0x30c
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

I don't have strong feelings either way for this, so:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
Mark.

> ---
> 
> Changes in v9:
> - Added to commit message that this doesn't catch all cases.
> 
> Changes in v8:
> - "Tag the arm64 idle functions as __cpuidle" new for v8
> 
>  arch/arm64/kernel/idle.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/idle.c b/arch/arm64/kernel/idle.c
> index c1125753fe9b..05cfb347ec26 100644
> --- a/arch/arm64/kernel/idle.c
> +++ b/arch/arm64/kernel/idle.c
> @@ -20,7 +20,7 @@
>   *	ensure that interrupts are not masked at the PMR (because the core will
>   *	not wake up if we block the wake up signal in the interrupt controller).
>   */
> -void noinstr cpu_do_idle(void)
> +void __cpuidle cpu_do_idle(void)
>  {
>  	struct arm_cpuidle_irq_context context;
>  
> @@ -35,7 +35,7 @@ void noinstr cpu_do_idle(void)
>  /*
>   * This is our default idle handler.
>   */
> -void noinstr arch_cpu_idle(void)
> +void __cpuidle arch_cpu_idle(void)
>  {
>  	/*
>  	 * This should do all the clock switching and wait for interrupt
> -- 
> 2.41.0.rc2.161.g9c6817b8e7-goog
>
diff mbox series

Patch

diff --git a/arch/arm64/kernel/idle.c b/arch/arm64/kernel/idle.c
index c1125753fe9b..05cfb347ec26 100644
--- a/arch/arm64/kernel/idle.c
+++ b/arch/arm64/kernel/idle.c
@@ -20,7 +20,7 @@ 
  *	ensure that interrupts are not masked at the PMR (because the core will
  *	not wake up if we block the wake up signal in the interrupt controller).
  */
-void noinstr cpu_do_idle(void)
+void __cpuidle cpu_do_idle(void)
 {
 	struct arm_cpuidle_irq_context context;
 
@@ -35,7 +35,7 @@  void noinstr cpu_do_idle(void)
 /*
  * This is our default idle handler.
  */
-void noinstr arch_cpu_idle(void)
+void __cpuidle arch_cpu_idle(void)
 {
 	/*
 	 * This should do all the clock switching and wait for interrupt