Messages in this thread Patch in this message | | | From | Xiongfeng Wang <> | Subject | [PATCH] irqchip/gic-v3-its: Select housekeeping CPUs preferentially for managed IRQs | Date | Mon, 24 Jan 2022 15:34:40 +0800 |
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When using kernel parameter 'isolcpus=managed_irq,xxxx' to bind the managed IRQs to housekeeping CPUs, the effective_affinity sometimes still contains the non-housekeeping CPUs.
irq_do_set_affinity() passes the housekeeping cpumask to chip->irq_set_affinity(), but ITS driver select CPU according to irq_common_data->affinity. While 'irq_common_data->affinity' is updated after chip->irq_set_affinity() is called in irq_do_set_affinity(). Also 'irq_common_data->affinity' may contains non-housekeeping CPUs. I found the below link explaining the reason. https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2267032.html
To modify CPU selecting logic to prefer housekeeping CPUs, select CPU from the input cpumask parameter first. If none of it is online, then select CPU from 'irq_common_data->affinity'.
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com> --- drivers/irqchip/irq-gic-v3-its.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c index d25b7a864bbb..17c15d3b2784 100644 --- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -1624,7 +1624,10 @@ static int its_select_cpu(struct irq_data *d, cpu = cpumask_pick_least_loaded(d, tmpmask); } else { - cpumask_and(tmpmask, irq_data_get_affinity_mask(d), cpu_online_mask); + cpumask_and(tmpmask, aff_mask, cpu_online_mask); + if (cpumask_empty(tmpmask)) + cpumask_and(tmpmask, irq_data_get_affinity_mask(d), + cpu_online_mask); /* If we cannot cross sockets, limit the search to that node */ if ((its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) && -- 2.20.1
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