* [PATCH v3] rcu/cpu_stall_cputime: fix the hardirq count for x86 architecture
@ 2025-02-16 8:41 Yongliang Gao
2025-02-17 2:29 ` Boqun Feng
0 siblings, 1 reply; 3+ messages in thread
From: Yongliang Gao @ 2025-02-16 8:41 UTC (permalink / raw)
To: Neeraj.Upadhyay, paulmck, frederic, thunder.leizhen
Cc: frankjpliu, kernelxing, rcu, linux-kernel, Yongliang Gao,
kernel test robot
From: Yongliang Gao <leonylgao@tencent.com>
When counting the number of hardirqs in the x86 architecture,
it is essential to add arch_irq_stat_cpu to ensure accuracy.
For example, a CPU loop within the rcu_read_lock function.
Before:
[ 70.910184] rcu: INFO: rcu_preempt self-detected stall on CPU
[ 70.910436] rcu: 3-....: (4999 ticks this GP) idle=***
[ 70.910711] rcu: hardirqs softirqs csw/system
[ 70.910870] rcu: number: 0 657 0
[ 70.911024] rcu: cputime: 0 0 2498 ==> 2498(ms)
[ 70.911278] rcu: (t=5001 jiffies g=3677 q=29 ncpus=8)
After:
[ 68.046132] rcu: INFO: rcu_preempt self-detected stall on CPU
[ 68.046354] rcu: 2-....: (4999 ticks this GP) idle=***
[ 68.046628] rcu: hardirqs softirqs csw/system
[ 68.046793] rcu: number: 2498 663 0
[ 68.046951] rcu: cputime: 0 0 2496 ==> 2496(ms)
[ 68.047244] rcu: (t=5000 jiffies g=3825 q=4 ncpus=8)
Fixes: be42f00b73a0 ("rcu: Add RCU stall diagnosis information")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501090842.SfI6QPGS-lkp@intel.com/
Signed-off-by: Yongliang Gao <leonylgao@tencent.com>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
---
Changes from v2:
- Add Reviewed-by 'Neeraj Upadhyay' information
- Link to v2: https://lore.kernel.org/all/20250109024652.1342595-1-leonylgao@gmail.com
Changes from v1:
- Fix compilation error when using arm64-allnoconfig/riscv-randconfig. [kernel test robot]
- Link to v1: https://lore.kernel.org/r/20250108065716.2888148-1-leonylgao%40gmail.com
---
---
kernel/rcu/tree.c | 10 +++++++---
kernel/rcu/tree.h | 2 +-
kernel/rcu/tree_stall.h | 4 ++--
3 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 475f31deed14..a0dab5923d03 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -781,6 +781,10 @@ static int rcu_watching_snap_save(struct rcu_data *rdp)
return 0;
}
+#ifndef arch_irq_stat_cpu
+#define arch_irq_stat_cpu(cpu) 0
+#endif
+
/*
* Returns positive if the specified CPU has passed through a quiescent state
* by virtue of being in or having passed through an dynticks idle state since
@@ -916,9 +920,9 @@ static int rcu_watching_snap_recheck(struct rcu_data *rdp)
rsrp->cputime_irq = kcpustat_field(kcsp, CPUTIME_IRQ, cpu);
rsrp->cputime_softirq = kcpustat_field(kcsp, CPUTIME_SOFTIRQ, cpu);
rsrp->cputime_system = kcpustat_field(kcsp, CPUTIME_SYSTEM, cpu);
- rsrp->nr_hardirqs = kstat_cpu_irqs_sum(rdp->cpu);
- rsrp->nr_softirqs = kstat_cpu_softirqs_sum(rdp->cpu);
- rsrp->nr_csw = nr_context_switches_cpu(rdp->cpu);
+ rsrp->nr_hardirqs = kstat_cpu_irqs_sum(cpu) + arch_irq_stat_cpu(cpu);
+ rsrp->nr_softirqs = kstat_cpu_softirqs_sum(cpu);
+ rsrp->nr_csw = nr_context_switches_cpu(cpu);
rsrp->jiffies = jiffies;
rsrp->gp_seq = rdp->gp_seq;
}
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index a9a811d9d7a3..1bba2225e744 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -168,7 +168,7 @@ struct rcu_snap_record {
u64 cputime_irq; /* Accumulated cputime of hard irqs */
u64 cputime_softirq;/* Accumulated cputime of soft irqs */
u64 cputime_system; /* Accumulated cputime of kernel tasks */
- unsigned long nr_hardirqs; /* Accumulated number of hard irqs */
+ u64 nr_hardirqs; /* Accumulated number of hard irqs */
unsigned int nr_softirqs; /* Accumulated number of soft irqs */
unsigned long long nr_csw; /* Accumulated number of task switches */
unsigned long jiffies; /* Track jiffies value */
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 925fcdad5dea..56b21219442b 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -435,8 +435,8 @@ static void print_cpu_stat_info(int cpu)
rsr.cputime_system = kcpustat_field(kcsp, CPUTIME_SYSTEM, cpu);
pr_err("\t hardirqs softirqs csw/system\n");
- pr_err("\t number: %8ld %10d %12lld\n",
- kstat_cpu_irqs_sum(cpu) - rsrp->nr_hardirqs,
+ pr_err("\t number: %8lld %10d %12lld\n",
+ kstat_cpu_irqs_sum(cpu) + arch_irq_stat_cpu(cpu) - rsrp->nr_hardirqs,
kstat_cpu_softirqs_sum(cpu) - rsrp->nr_softirqs,
nr_context_switches_cpu(cpu) - rsrp->nr_csw);
pr_err("\tcputime: %8lld %10lld %12lld ==> %d(ms)\n",
--
2.39.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v3] rcu/cpu_stall_cputime: fix the hardirq count for x86 architecture
2025-02-16 8:41 [PATCH v3] rcu/cpu_stall_cputime: fix the hardirq count for x86 architecture Yongliang Gao
@ 2025-02-17 2:29 ` Boqun Feng
2025-03-05 16:43 ` Boqun Feng
0 siblings, 1 reply; 3+ messages in thread
From: Boqun Feng @ 2025-02-17 2:29 UTC (permalink / raw)
To: Yongliang Gao
Cc: Neeraj.Upadhyay, paulmck, frederic, thunder.leizhen, frankjpliu,
kernelxing, rcu, linux-kernel, Yongliang Gao, kernel test robot,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin
Hi Yongliang,
On Sun, Feb 16, 2025 at 04:41:09PM +0800, Yongliang Gao wrote:
> From: Yongliang Gao <leonylgao@tencent.com>
>
> When counting the number of hardirqs in the x86 architecture,
> it is essential to add arch_irq_stat_cpu to ensure accuracy.
>
> For example, a CPU loop within the rcu_read_lock function.
>
> Before:
> [ 70.910184] rcu: INFO: rcu_preempt self-detected stall on CPU
> [ 70.910436] rcu: 3-....: (4999 ticks this GP) idle=***
> [ 70.910711] rcu: hardirqs softirqs csw/system
> [ 70.910870] rcu: number: 0 657 0
> [ 70.911024] rcu: cputime: 0 0 2498 ==> 2498(ms)
> [ 70.911278] rcu: (t=5001 jiffies g=3677 q=29 ncpus=8)
>
> After:
> [ 68.046132] rcu: INFO: rcu_preempt self-detected stall on CPU
> [ 68.046354] rcu: 2-....: (4999 ticks this GP) idle=***
> [ 68.046628] rcu: hardirqs softirqs csw/system
> [ 68.046793] rcu: number: 2498 663 0
> [ 68.046951] rcu: cputime: 0 0 2496 ==> 2496(ms)
> [ 68.047244] rcu: (t=5000 jiffies g=3825 q=4 ncpus=8)
>
> Fixes: be42f00b73a0 ("rcu: Add RCU stall diagnosis information")
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202501090842.SfI6QPGS-lkp@intel.com/
> Signed-off-by: Yongliang Gao <leonylgao@tencent.com>
> Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
>
Thank you for the patch, I have one minor question to x86 maintainers
(Cced): does it make sense to fold the sum of arch_irq_stat_cpu() into
kstat_cpu_irqs_sum()?
Regards,
Boqun
> ---
> Changes from v2:
> - Add Reviewed-by 'Neeraj Upadhyay' information
> - Link to v2: https://lore.kernel.org/all/20250109024652.1342595-1-leonylgao@gmail.com
> Changes from v1:
> - Fix compilation error when using arm64-allnoconfig/riscv-randconfig. [kernel test robot]
> - Link to v1: https://lore.kernel.org/r/20250108065716.2888148-1-leonylgao%40gmail.com
> ---
> ---
> kernel/rcu/tree.c | 10 +++++++---
> kernel/rcu/tree.h | 2 +-
> kernel/rcu/tree_stall.h | 4 ++--
> 3 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 475f31deed14..a0dab5923d03 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -781,6 +781,10 @@ static int rcu_watching_snap_save(struct rcu_data *rdp)
> return 0;
> }
>
> +#ifndef arch_irq_stat_cpu
> +#define arch_irq_stat_cpu(cpu) 0
> +#endif
> +
> /*
> * Returns positive if the specified CPU has passed through a quiescent state
> * by virtue of being in or having passed through an dynticks idle state since
> @@ -916,9 +920,9 @@ static int rcu_watching_snap_recheck(struct rcu_data *rdp)
> rsrp->cputime_irq = kcpustat_field(kcsp, CPUTIME_IRQ, cpu);
> rsrp->cputime_softirq = kcpustat_field(kcsp, CPUTIME_SOFTIRQ, cpu);
> rsrp->cputime_system = kcpustat_field(kcsp, CPUTIME_SYSTEM, cpu);
> - rsrp->nr_hardirqs = kstat_cpu_irqs_sum(rdp->cpu);
> - rsrp->nr_softirqs = kstat_cpu_softirqs_sum(rdp->cpu);
> - rsrp->nr_csw = nr_context_switches_cpu(rdp->cpu);
> + rsrp->nr_hardirqs = kstat_cpu_irqs_sum(cpu) + arch_irq_stat_cpu(cpu);
> + rsrp->nr_softirqs = kstat_cpu_softirqs_sum(cpu);
> + rsrp->nr_csw = nr_context_switches_cpu(cpu);
> rsrp->jiffies = jiffies;
> rsrp->gp_seq = rdp->gp_seq;
> }
> diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
> index a9a811d9d7a3..1bba2225e744 100644
> --- a/kernel/rcu/tree.h
> +++ b/kernel/rcu/tree.h
> @@ -168,7 +168,7 @@ struct rcu_snap_record {
> u64 cputime_irq; /* Accumulated cputime of hard irqs */
> u64 cputime_softirq;/* Accumulated cputime of soft irqs */
> u64 cputime_system; /* Accumulated cputime of kernel tasks */
> - unsigned long nr_hardirqs; /* Accumulated number of hard irqs */
> + u64 nr_hardirqs; /* Accumulated number of hard irqs */
> unsigned int nr_softirqs; /* Accumulated number of soft irqs */
> unsigned long long nr_csw; /* Accumulated number of task switches */
> unsigned long jiffies; /* Track jiffies value */
> diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
> index 925fcdad5dea..56b21219442b 100644
> --- a/kernel/rcu/tree_stall.h
> +++ b/kernel/rcu/tree_stall.h
> @@ -435,8 +435,8 @@ static void print_cpu_stat_info(int cpu)
> rsr.cputime_system = kcpustat_field(kcsp, CPUTIME_SYSTEM, cpu);
>
> pr_err("\t hardirqs softirqs csw/system\n");
> - pr_err("\t number: %8ld %10d %12lld\n",
> - kstat_cpu_irqs_sum(cpu) - rsrp->nr_hardirqs,
> + pr_err("\t number: %8lld %10d %12lld\n",
> + kstat_cpu_irqs_sum(cpu) + arch_irq_stat_cpu(cpu) - rsrp->nr_hardirqs,
> kstat_cpu_softirqs_sum(cpu) - rsrp->nr_softirqs,
> nr_context_switches_cpu(cpu) - rsrp->nr_csw);
> pr_err("\tcputime: %8lld %10lld %12lld ==> %d(ms)\n",
> --
> 2.39.3
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v3] rcu/cpu_stall_cputime: fix the hardirq count for x86 architecture
2025-02-17 2:29 ` Boqun Feng
@ 2025-03-05 16:43 ` Boqun Feng
0 siblings, 0 replies; 3+ messages in thread
From: Boqun Feng @ 2025-03-05 16:43 UTC (permalink / raw)
To: Yongliang Gao
Cc: Neeraj.Upadhyay, paulmck, frederic, thunder.leizhen, frankjpliu,
kernelxing, rcu, linux-kernel, Yongliang Gao, kernel test robot,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin
On Sun, Feb 16, 2025 at 06:29:54PM -0800, Boqun Feng wrote:
> Hi Yongliang,
>
> On Sun, Feb 16, 2025 at 04:41:09PM +0800, Yongliang Gao wrote:
> > From: Yongliang Gao <leonylgao@tencent.com>
> >
> > When counting the number of hardirqs in the x86 architecture,
> > it is essential to add arch_irq_stat_cpu to ensure accuracy.
> >
> > For example, a CPU loop within the rcu_read_lock function.
> >
> > Before:
> > [ 70.910184] rcu: INFO: rcu_preempt self-detected stall on CPU
> > [ 70.910436] rcu: 3-....: (4999 ticks this GP) idle=***
> > [ 70.910711] rcu: hardirqs softirqs csw/system
> > [ 70.910870] rcu: number: 0 657 0
> > [ 70.911024] rcu: cputime: 0 0 2498 ==> 2498(ms)
> > [ 70.911278] rcu: (t=5001 jiffies g=3677 q=29 ncpus=8)
> >
> > After:
> > [ 68.046132] rcu: INFO: rcu_preempt self-detected stall on CPU
> > [ 68.046354] rcu: 2-....: (4999 ticks this GP) idle=***
> > [ 68.046628] rcu: hardirqs softirqs csw/system
> > [ 68.046793] rcu: number: 2498 663 0
> > [ 68.046951] rcu: cputime: 0 0 2496 ==> 2496(ms)
> > [ 68.047244] rcu: (t=5000 jiffies g=3825 q=4 ncpus=8)
> >
> > Fixes: be42f00b73a0 ("rcu: Add RCU stall diagnosis information")
> > Reported-by: kernel test robot <lkp@intel.com>
> > Closes: https://lore.kernel.org/oe-kbuild-all/202501090842.SfI6QPGS-lkp@intel.com/
> > Signed-off-by: Yongliang Gao <leonylgao@tencent.com>
> > Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
> >
>
> Thank you for the patch, I have one minor question to x86 maintainers
> (Cced): does it make sense to fold the sum of arch_irq_stat_cpu() into
> kstat_cpu_irqs_sum()?
>
Queued for further tests and reviews, but my question for x86
maintainers remains ;-)
Regards,
Boqun
> Regards,
> Boqun
>
> > ---
> > Changes from v2:
> > - Add Reviewed-by 'Neeraj Upadhyay' information
> > - Link to v2: https://lore.kernel.org/all/20250109024652.1342595-1-leonylgao@gmail.com
> > Changes from v1:
> > - Fix compilation error when using arm64-allnoconfig/riscv-randconfig. [kernel test robot]
> > - Link to v1: https://lore.kernel.org/r/20250108065716.2888148-1-leonylgao%40gmail.com
> > ---
> > ---
> > kernel/rcu/tree.c | 10 +++++++---
> > kernel/rcu/tree.h | 2 +-
> > kernel/rcu/tree_stall.h | 4 ++--
> > 3 files changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 475f31deed14..a0dab5923d03 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -781,6 +781,10 @@ static int rcu_watching_snap_save(struct rcu_data *rdp)
> > return 0;
> > }
> >
> > +#ifndef arch_irq_stat_cpu
> > +#define arch_irq_stat_cpu(cpu) 0
> > +#endif
> > +
> > /*
> > * Returns positive if the specified CPU has passed through a quiescent state
> > * by virtue of being in or having passed through an dynticks idle state since
> > @@ -916,9 +920,9 @@ static int rcu_watching_snap_recheck(struct rcu_data *rdp)
> > rsrp->cputime_irq = kcpustat_field(kcsp, CPUTIME_IRQ, cpu);
> > rsrp->cputime_softirq = kcpustat_field(kcsp, CPUTIME_SOFTIRQ, cpu);
> > rsrp->cputime_system = kcpustat_field(kcsp, CPUTIME_SYSTEM, cpu);
> > - rsrp->nr_hardirqs = kstat_cpu_irqs_sum(rdp->cpu);
> > - rsrp->nr_softirqs = kstat_cpu_softirqs_sum(rdp->cpu);
> > - rsrp->nr_csw = nr_context_switches_cpu(rdp->cpu);
> > + rsrp->nr_hardirqs = kstat_cpu_irqs_sum(cpu) + arch_irq_stat_cpu(cpu);
> > + rsrp->nr_softirqs = kstat_cpu_softirqs_sum(cpu);
> > + rsrp->nr_csw = nr_context_switches_cpu(cpu);
> > rsrp->jiffies = jiffies;
> > rsrp->gp_seq = rdp->gp_seq;
> > }
> > diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
> > index a9a811d9d7a3..1bba2225e744 100644
> > --- a/kernel/rcu/tree.h
> > +++ b/kernel/rcu/tree.h
> > @@ -168,7 +168,7 @@ struct rcu_snap_record {
> > u64 cputime_irq; /* Accumulated cputime of hard irqs */
> > u64 cputime_softirq;/* Accumulated cputime of soft irqs */
> > u64 cputime_system; /* Accumulated cputime of kernel tasks */
> > - unsigned long nr_hardirqs; /* Accumulated number of hard irqs */
> > + u64 nr_hardirqs; /* Accumulated number of hard irqs */
> > unsigned int nr_softirqs; /* Accumulated number of soft irqs */
> > unsigned long long nr_csw; /* Accumulated number of task switches */
> > unsigned long jiffies; /* Track jiffies value */
> > diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
> > index 925fcdad5dea..56b21219442b 100644
> > --- a/kernel/rcu/tree_stall.h
> > +++ b/kernel/rcu/tree_stall.h
> > @@ -435,8 +435,8 @@ static void print_cpu_stat_info(int cpu)
> > rsr.cputime_system = kcpustat_field(kcsp, CPUTIME_SYSTEM, cpu);
> >
> > pr_err("\t hardirqs softirqs csw/system\n");
> > - pr_err("\t number: %8ld %10d %12lld\n",
> > - kstat_cpu_irqs_sum(cpu) - rsrp->nr_hardirqs,
> > + pr_err("\t number: %8lld %10d %12lld\n",
> > + kstat_cpu_irqs_sum(cpu) + arch_irq_stat_cpu(cpu) - rsrp->nr_hardirqs,
> > kstat_cpu_softirqs_sum(cpu) - rsrp->nr_softirqs,
> > nr_context_switches_cpu(cpu) - rsrp->nr_csw);
> > pr_err("\tcputime: %8lld %10lld %12lld ==> %d(ms)\n",
> > --
> > 2.39.3
> >
> >
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2025-02-16 8:41 [PATCH v3] rcu/cpu_stall_cputime: fix the hardirq count for x86 architecture Yongliang Gao
2025-02-17 2:29 ` Boqun Feng
2025-03-05 16:43 ` Boqun Feng
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