lkml.org 
[lkml]   [2018]   [Sep]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH] genirq: Avoid race between cpu hot plug and irq_desc() allocation paths
On 2018-09-05 11:23, Thomas Gleixner wrote:
> On Wed, 5 Sep 2018, Prakruthi Deepak Heragu wrote:
>
>> One of the cores might have just allocated irq_desc() and other core
>> might be doing irq migration in the hot plug path. In the hot plug
>> path
>> during the IRQ migration, for_each_active_irq macro is trying to get
>> irqs whose bits are set in allocated_irqs bit map but there is no
>> return
>> value check after irq_to_desc for desc validity.
>
> Confused. All parts involved, irq allocation/deallocation and the CPU
> hotplug code take sparse_irq_lock to prevent exavtly that.
>
Removing the NULL pointer check and adding this sparse_irq_lock
that you suggested will solve this issue. The code looks like
this now. Is this okay?
diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index 9409b55..f2ef76e 100644
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -185,14 +185,10 @@ void irq_migrate_all_off_this_cpu(void)
{
struct irq_desc *desc;
unsigned int irq;
-
+ irq_lock_sparse();
for_each_active_irq(irq) {
bool affinity_broken;
-
desc = irq_to_desc(irq);
- if (!desc)
- continue;
-
raw_spin_lock(&desc->lock);
affinity_broken = migrate_one_irq(desc);
raw_spin_unlock(&desc->lock);
@@ -202,6 +198,7 @@ void irq_migrate_all_off_this_cpu(void)
irq, smp_processor_id());
}
}
+ irq_unlock_sparse();
}

static void irq_restore_affinity_of_irq(struct irq_desc *desc, unsigned
int cpu)
> Thanks,
>
> tglx

Thanks,
Prakruthi Deepak Heragu

\
 
 \ /
  Last update: 2018-09-06 01:28    [W:0.069 / U:0.732 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site