From: Yongliang Gao <leonyl...@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 <l...@intel.com>
Closes:
https://lore.kernel.org/oe-kbuild-all/202501090842.sfi6qpgs-...@intel.com/
Signed-off-by: Yongliang Gao <leonyl...@tencent.com>
Reviewed-by: Neeraj Upadhyay <neeraj.upadh...@amd.com>
---
Changes from v2:
- Add Reviewed-by 'Neeraj Upadhyay' information
- Link to v2:
https://lore.kernel.org/all/20250109024652.1342595-1-leonyl...@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
