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Subject[RFC] irq: Skip printing irq when desc->action is null even if any_count is not zero
Date
From: LiuChao <liuchao173@huawei.com>

When desc->action is empty, there is no need to print out the irq and its'
count in each cpu. The desc is not alloced in request_irq or freed in
free_irq. So some PCI devices, such as rtl8139, uses request_irq and
free_irq, which only modify the action of desc. So /proc/interrupts could
be like this:

CPU0 CPU1
2: 69397 69267 GICv3 27 Level arch_timer
4: 0 0 GICv3 33 Level uart-pl011
38: 46 0 GICv3 36 Level ehci_hcd:usb1
39: 66 0 GICv3 37 Level
40: 0 0 GICv3 38 Level virtio1
42: 0 0 GICv3 23 Level arm-pmu
43: 0 0 ARMH0061:00 3 Edge ACPI:Event
44: 1 0 ITS-MSI 32768 Edge PCIe PME, pciehp
45: 0 0 ITS-MSI 32769 Edge aerdrv

Irqbalance gets the list of interrupts according to /proc/interrupts. In
this case, irqbalance does not remove the interrupt from the balance list,
and the last string in this line,which is Level, is used as irq_name.

Or we can clear desc->kstat_irqs in each cpu in free_irq when desc->action
is null?

Signed-off-by: LiuChao <liuchao173@huawei.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
---
kernel/irq/proc.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index cfc4f088a0e7..b27169e587f4 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -439,7 +439,7 @@ int show_interrupts(struct seq_file *p, void *v)
{
static int prec;

- unsigned long flags, any_count = 0;
+ unsigned long flags;
int i = *(loff_t *) v, j;
struct irqaction *action;
struct irq_desc *desc;
@@ -466,11 +466,7 @@ int show_interrupts(struct seq_file *p, void *v)
if (!desc)
goto outsparse;

- if (desc->kstat_irqs)
- for_each_online_cpu(j)
- any_count |= *per_cpu_ptr(desc->kstat_irqs, j);
-
- if ((!desc->action || irq_desc_is_chained(desc)) && !any_count)
+ if (!desc->action || irq_desc_is_chained(desc))
goto outsparse;

seq_printf(p, "%*d: ", prec, i);
--
2.19.1
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