arch/arm/kernel/smp.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
It is similar to ARM64 commit 916b93f4e865 ("arm64: smp: Fix missing IPI
statistics"), commit 56afcd3dbd19 ("ARM: Allow IPIs to be handled as normal
interrupts") set CPU_BACKTRACE IPI "IRQ_HIDDEN" flag but not show it in
show_ipi_list(), which cause the interrupt kstat_irqs accounting
is missing in display.
Before this patch, CPU_BACKTRACE IPI is missing (QEMU vexpress-a9):
# cat /proc/interrupts
CPU0
24: 6 GIC-0 34 Level timer
25: 455 GIC-0 29 Level twd
26: 42 GIC-0 75 Edge virtio0
29: 8 GIC-0 44 Level kmi-pl050
30: 118 GIC-0 45 Level kmi-pl050
31: 0 GIC-0 36 Level rtc-pl031
32: 0 GIC-0 41 Level mmci-pl18x (cmd)
33: 0 GIC-0 42 Level mmci-pl18x (pio)
34: 0 GIC-0 92 Level arm-pmu
35: 0 GIC-0 93 Level arm-pmu
36: 0 GIC-0 94 Level arm-pmu
37: 0 GIC-0 95 Level arm-pmu
39: 15 GIC-0 37 Level uart-pl011
IPI0: 0 CPU wakeup interrupts
IPI1: 0 Timer broadcast interrupts
IPI2: 0 Rescheduling interrupts
IPI3: 0 Function call interrupts
IPI4: 0 CPU stop interrupts
IPI5: 0 IRQ work interrupts
IPI6: 0 completion interrupts
Err: 0
After this pacth, CPU_BACKTRACE IPI is displayed:
# cat /proc/interrupts
CPU0
24: 6 GIC-0 34 Level timer
25: 687 GIC-0 29 Level twd
26: 42 GIC-0 75 Edge virtio0
29: 8 GIC-0 44 Level kmi-pl050
30: 134 GIC-0 45 Level kmi-pl050
31: 0 GIC-0 36 Level rtc-pl031
32: 0 GIC-0 41 Level mmci-pl18x (cmd)
33: 0 GIC-0 42 Level mmci-pl18x (pio)
34: 0 GIC-0 92 Level arm-pmu
35: 0 GIC-0 93 Level arm-pmu
36: 0 GIC-0 94 Level arm-pmu
37: 0 GIC-0 95 Level arm-pmu
39: 29 GIC-0 37 Level uart-pl011
IPI0: 0 CPU wakeup interrupts
IPI1: 0 Timer broadcast interrupts
IPI2: 0 Rescheduling interrupts
IPI3: 0 Function call interrupts
IPI4: 0 CPU stop interrupts
IPI5: 0 IRQ work interrupts
IPI6: 0 completion interrupts
IPI7: 0 CPU backtrace interrupts
Err: 0
Fixes: 56afcd3dbd19 ("ARM: Allow IPIs to be handled as normal interrupts")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
arch/arm/kernel/smp.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 3431c0553f45..be15cca7f8d7 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -531,7 +531,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
}
}
-static const char *ipi_types[NR_IPI] __tracepoint_string = {
+static const char *ipi_types[MAX_IPI] __tracepoint_string = {
[IPI_WAKEUP] = "CPU wakeup interrupts",
[IPI_TIMER] = "Timer broadcast interrupts",
[IPI_RESCHEDULE] = "Rescheduling interrupts",
@@ -539,6 +539,7 @@ static const char *ipi_types[NR_IPI] __tracepoint_string = {
[IPI_CPU_STOP] = "CPU stop interrupts",
[IPI_IRQ_WORK] = "IRQ work interrupts",
[IPI_COMPLETION] = "completion interrupts",
+ [IPI_CPU_BACKTRACE] = "CPU backtrace interrupts"
};
static void smp_cross_call(const struct cpumask *target, unsigned int ipinr);
@@ -547,7 +548,7 @@ void show_ipi_list(struct seq_file *p, int prec)
{
unsigned int cpu, i;
- for (i = 0; i < NR_IPI; i++) {
+ for (i = 0; i < MAX_IPI; i++) {
if (!ipi_desc[i])
continue;
--
2.34.1On Thu, Aug 01, 2024 at 05:40:22PM +0800, Jinjie Ruan wrote:
> It is similar to ARM64 commit 916b93f4e865 ("arm64: smp: Fix missing IPI
> statistics"), commit 56afcd3dbd19 ("ARM: Allow IPIs to be handled as normal
> interrupts") set CPU_BACKTRACE IPI "IRQ_HIDDEN" flag but not show it in
> show_ipi_list(), which cause the interrupt kstat_irqs accounting
> is missing in display.
I don't see why this needs to be included. If this IPI fires, it means
that the kernel has suffered a lockup and is probably not very useful.
So the chances of being able to read out from /proc/interrupts a non-
zero "CPU backtrace interrupts" figure is highly unlikely.
So, I don't see much point to this change.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
On 2024/8/2 0:36, Russell King (Oracle) wrote:
> On Thu, Aug 01, 2024 at 05:40:22PM +0800, Jinjie Ruan wrote:
>> It is similar to ARM64 commit 916b93f4e865 ("arm64: smp: Fix missing IPI
>> statistics"), commit 56afcd3dbd19 ("ARM: Allow IPIs to be handled as normal
>> interrupts") set CPU_BACKTRACE IPI "IRQ_HIDDEN" flag but not show it in
>> show_ipi_list(), which cause the interrupt kstat_irqs accounting
>> is missing in display.
>
> I don't see why this needs to be included. If this IPI fires, it means
> that the kernel has suffered a lockup and is probably not very useful.
> So the chances of being able to read out from /proc/interrupts a non-
> zero "CPU backtrace interrupts" figure is highly unlikely.
It is more of a change than a bug.
If we reset the arm32 code to before commit 56afcd3dbd19 ("ARM: Allow
IPIs to be handled as normal interrupts"), the backtrace IPI statics is
shown ok as below, but after that it is missing:
/ # cat /proc/interrupts
CPU0
24: 6 GIC-0 34 Level timer
25: 469 GIC-0 29 Level twd
26: 61 GIC-0 75 Edge virtio0
29: 8 GIC-0 44 Level kmi-pl050
30: 118 GIC-0 45 Level kmi-pl050
31: 0 GIC-0 36 Level rtc-pl031
32: 0 GIC-0 41 Level mmci-pl18x (cmd)
33: 0 GIC-0 42 Level mmci-pl18x (pio)
34: 0 GIC-0 92 Level arm-pmu
35: 0 GIC-0 93 Level arm-pmu
36: 0 GIC-0 94 Level arm-pmu
37: 0 GIC-0 95 Level arm-pmu
39: 15 GIC-0 37 Level uart-pl011
IPI0: 0 CPU wakeup interrupts
IPI1: 0 Timer broadcast interrupts
IPI2: 0 Rescheduling interrupts
IPI3: 0 Function call interrupts
IPI4: 0 CPU stop interrupts
IPI5: 0 IRQ work interrupts
IPI6: 0 completion interrupts
IPI7: 0 CPU backtrace interrupts
>
> So, I don't see much point to this change.
>
On 2024/8/2 9:39, Jinjie Ruan wrote:
>
>
> On 2024/8/2 0:36, Russell King (Oracle) wrote:
>> On Thu, Aug 01, 2024 at 05:40:22PM +0800, Jinjie Ruan wrote:
>>> It is similar to ARM64 commit 916b93f4e865 ("arm64: smp: Fix missing IPI
>>> statistics"), commit 56afcd3dbd19 ("ARM: Allow IPIs to be handled as normal
>>> interrupts") set CPU_BACKTRACE IPI "IRQ_HIDDEN" flag but not show it in
>>> show_ipi_list(), which cause the interrupt kstat_irqs accounting
>>> is missing in display.
>>
>> I don't see why this needs to be included. If this IPI fires, it means
>> that the kernel has suffered a lockup and is probably not very useful.
>> So the chances of being able to read out from /proc/interrupts a non-
>> zero "CPU backtrace interrupts" figure is highly unlikely.
>
> It is more of a change than a bug.
>
> If we reset the arm32 code to before commit 56afcd3dbd19 ("ARM: Allow
> IPIs to be handled as normal interrupts"), the backtrace IPI statics is
> shown ok as below, but after that it is missing:
Sorry, there is some mistake here, the original result has no backtrace
IPI statics.
>
> / # cat /proc/interrupts
> CPU0
> 24: 6 GIC-0 34 Level timer
> 25: 469 GIC-0 29 Level twd
> 26: 61 GIC-0 75 Edge virtio0
> 29: 8 GIC-0 44 Level kmi-pl050
> 30: 118 GIC-0 45 Level kmi-pl050
> 31: 0 GIC-0 36 Level rtc-pl031
> 32: 0 GIC-0 41 Level mmci-pl18x (cmd)
> 33: 0 GIC-0 42 Level mmci-pl18x (pio)
> 34: 0 GIC-0 92 Level arm-pmu
> 35: 0 GIC-0 93 Level arm-pmu
> 36: 0 GIC-0 94 Level arm-pmu
> 37: 0 GIC-0 95 Level arm-pmu
> 39: 15 GIC-0 37 Level uart-pl011
> IPI0: 0 CPU wakeup interrupts
> IPI1: 0 Timer broadcast interrupts
> IPI2: 0 Rescheduling interrupts
> IPI3: 0 Function call interrupts
> IPI4: 0 CPU stop interrupts
> IPI5: 0 IRQ work interrupts
> IPI6: 0 completion interrupts
> IPI7: 0 CPU backtrace interrupts
>
>
>>
>> So, I don't see much point to this change.
>>
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