Messages in this thread | | | Subject | Re: [PATCH] genirq/proc: Show percpu irq affinity | From | Yunfeng Ye <> | Date | Sat, 22 Aug 2020 17:33:39 +0800 |
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On 2020/8/13 16:27, Thomas Gleixner wrote: > Yunfeng Ye <yeyunfeng@huawei.com> writes: > >> When the "affinity=" cmdline parameter is configured, > > There is no such parameter. > >> the interrupt affinity displayed in the proc directory does not match >> with that of the the percu interrupt, and the percu interrupt uses >> desc->percu_affinity. > > And when the non-existing parameter is not on the command line then > irq->affinity is showing the correct value magically? > > Definitely not: It's unconditionally showing irq->affinity and that is > pretty unlikely to match irq->percpu_affinity in any case. > Sorry,it is "irqaffinity=" cmdline parameter. it will set irq_default_affinity mask. if the interrupt is not the managed irq, the irq_desc will use irq_default_affinity as default affinity.
For example, the cmdline "irqaffinity=0,1,126,127" on the 128 cores system:
[root@localhost ~]# cat /proc/irq/4/smp_affinity_list 0-1,126-127
The irq 4 is "arch_timer" interrupt, which is a percpu interrupt.
So is it necessary to show the percpu irq affinity correct?
thanks.
>> diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c >> index 32c071d7bc03..b9d0fa87b4b4 100644 >> --- a/kernel/irq/proc.c >> +++ b/kernel/irq/proc.c >> @@ -52,6 +52,8 @@ static int show_irq_affinity(int type, struct seq_file *m) >> case AFFINITY: >> case AFFINITY_LIST: >> mask = desc->irq_common_data.affinity; >> + if (irqd_is_per_cpu(&desc->irq_data)) >> + mask = desc->percpu_affinity; > > This breaks all architecture which mark interrupts as per CPU without > using the partition mechanism resulting in a NULL pointer dereference. > Yes, it is a problem.
> Thanks, > > tglx > > . >
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