| Message ID | 20230601143109.v9.2.I4baba13e220bdd24d11400c67f137c35f07f82c7@changeid (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Add debug IPI for backtraces / kgdb; try to use NMI for it | expand |
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 --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
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(-)