linux-kernel - Re: WARNING and PANIC in irq_matrix

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Date:   Thu, 22 Feb 2018 22:38:49 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tariq Toukan <tariqt@...lanox.com>
cc:     linux-kernel@...r.kernel.org, Maor Gottlieb <maorg@...lanox.com>
Subject: Re: WARNING and PANIC in irq_matrix_free

On Wed, 21 Feb 2018, Tariq Toukan wrote:
> On 20/02/2018 8:18 PM, Thomas Gleixner wrote:
> > On Tue, 20 Feb 2018, Thomas Gleixner wrote:
> > > On Tue, 20 Feb 2018, Tariq Toukan wrote:
> > > 
> > > Is there CPU hotplugging in play?
> 
> No.

Ok.

> > > 
> > > I'll come back to you tomorrow with a plan how to debug that after staring
> > > into the code some more.
> > 
> > Do you have a rough idea what the test case is doing?
> > 
> 
> It arbitrary appears in different flows, like sending traffic or interface
> configuration changes.

Hmm. Looks like memory corruption, but I can't pin point it.

Find below a debug patch which should prevent the crash and might give us
some insight into the type of corruption.

Please enable the irq_matrix and vector allocation trace points. 

echo 1 >/sys/kernel/debug/tracing/events/irq_matrix/enable
echo 1 >/sys/kernel/debug/tracing/events/irq_vectors/vector*/enable

When the problem triggers the bogus vector is printed and the trace is
frozen. Please provide dmesg and the tracebuffer output.

Thanks,

	tglx

8<--------------
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -822,6 +822,12 @@ static void free_moved_vector(struct api
 	unsigned int cpu = apicd->prev_cpu;
 	bool managed = apicd->is_managed;
 
+	if (vector < FIRST_EXTERNAL_VECTOR || vector >= FIRST_SYSTEM_VECTOR) {
+		tracing_off();
+		pr_err("Trying to clear prev_vector: %u\n", vector);
+		goto out;
+	}
+
 	/*
 	 * This should never happen. Managed interrupts are not
 	 * migrated except on CPU down, which does not involve the
@@ -833,6 +839,7 @@ static void free_moved_vector(struct api
 	trace_vector_free_moved(apicd->irq, cpu, vector, managed);
 	irq_matrix_free(vector_matrix, cpu, vector, managed);
 	per_cpu(vector_irq, cpu)[vector] = VECTOR_UNUSED;
+out:
 	hlist_del_init(&apicd->clist);
 	apicd->prev_vector = 0;
 	apicd->move_in_progress = 0;