Messages in this thread Patch in this message | | | Date | Wed, 05 Sep 2018 16:27:09 -0700 | From | pheragu@codeauro ... | Subject | Re: [PATCH] genirq: Avoid race between cpu hot plug and irq_desc() allocation paths |
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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
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