diff mbox

[v2] arm: use irq_set_affinity with force=false when migrating irqs

Message ID 1409581297-29216-1-git-send-email-sudeep.holla@arm.com (mailing list archive)
State New, archived
Headers show

Commit Message

Sudeep Holla Sept. 1, 2014, 2:21 p.m. UTC
From: Sudeep Holla <sudeep.holla@arm.com>

Since commit 1dbfa187dad ("ARM: irq migration: force migration off CPU
going down") the ARM interrupt migration code on cpu offline calls
irqchip.irq_set_affinity() with the argument force=true. At the point
of this change the argument had no effect because it was not used by
any interrupt chip driver and there was no semantics defined.

This changed with commit 01f8fa4f01d8 ("genirq: Allow forcing cpu
affinity of interrupts") which made the force argument useful to route
interrupts to not yet online cpus without checking the target cpu
against the cpu online mask. The following commit ffde1de64012
("irqchip: gic: Support forced affinity setting") implemented this for
the GIC interrupt controller.

As a consequence the ARM cpu offline irq migration fails if CPU0 is
offlined, because CPU0 is still set in the affinity mask and the
validataion against cpu online mask is skipped to the force argument
being true. The following first_cpu(mask) selection always selects
CPU0 as the target.

Solve the issue by calling irq_set_affinity() with force=false from
the CPU offline irq migration code so the GIC driver validates the
affinity mask against CPU online mask and therefore removes CPU0 from
the possible target candidates.

Tested on TC2 hotpluging CPU0 in and out. Without this patch the system
locks up as the IRQs are not migrated away from CPU0.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: <stable@vger.kernel.org> # 3.10.x
---
 arch/arm/kernel/irq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Change v1->v2:
 - Updated the changelog to reflect the actual history behind
   this change as suggested by tglx and added his ack

Comments

Mark Rutland Sept. 1, 2014, 3:50 p.m. UTC | #1
On Mon, Sep 01, 2014 at 03:21:37PM +0100, Sudeep Holla wrote:
> From: Sudeep Holla <sudeep.holla@arm.com>
> 
> Since commit 1dbfa187dad ("ARM: irq migration: force migration off CPU
> going down") the ARM interrupt migration code on cpu offline calls
> irqchip.irq_set_affinity() with the argument force=true. At the point
> of this change the argument had no effect because it was not used by
> any interrupt chip driver and there was no semantics defined.
> 
> This changed with commit 01f8fa4f01d8 ("genirq: Allow forcing cpu
> affinity of interrupts") which made the force argument useful to route
> interrupts to not yet online cpus without checking the target cpu
> against the cpu online mask. The following commit ffde1de64012
> ("irqchip: gic: Support forced affinity setting") implemented this for
> the GIC interrupt controller.
> 
> As a consequence the ARM cpu offline irq migration fails if CPU0 is
> offlined, because CPU0 is still set in the affinity mask and the
> validataion against cpu online mask is skipped to the force argument
> being true. The following first_cpu(mask) selection always selects
> CPU0 as the target.
> 
> Solve the issue by calling irq_set_affinity() with force=false from
> the CPU offline irq migration code so the GIC driver validates the
> affinity mask against CPU online mask and therefore removes CPU0 from
> the possible target candidates.
> 
> Tested on TC2 hotpluging CPU0 in and out. Without this patch the system
> locks up as the IRQs are not migrated away from CPU0.
> 
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> Acked-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: <stable@vger.kernel.org> # 3.10.x

Acked-by: Mark Rutland <mark.rutland@arm.com>

It's nice to finally know what we should be doing here. :)

Would you be able to take a look at doing the same for arm64? The
current solution (now in -stable) allows for hotplugging CPU0 but IIRC
it would break the affinity mask unnecessarily.

Cheers,
Mark.

> ---
>  arch/arm/kernel/irq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Change v1->v2:
>  - Updated the changelog to reflect the actual history behind
>    this change as suggested by tglx and added his ack
> 
> diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
> index 2c4257604513..5c4d38e32a51 100644
> --- a/arch/arm/kernel/irq.c
> +++ b/arch/arm/kernel/irq.c
> @@ -175,7 +175,7 @@ static bool migrate_one_irq(struct irq_desc *desc)
>  	c = irq_data_get_irq_chip(d);
>  	if (!c->irq_set_affinity)
>  		pr_debug("IRQ%u: unable to set affinity\n", d->irq);
> -	else if (c->irq_set_affinity(d, affinity, true) == IRQ_SET_MASK_OK && ret)
> +	else if (c->irq_set_affinity(d, affinity, false) == IRQ_SET_MASK_OK && ret)
>  		cpumask_copy(d->affinity, affinity);
>  
>  	return ret;
> -- 
> 1.8.3.2
>
diff mbox

Patch

diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
index 2c4257604513..5c4d38e32a51 100644
--- a/arch/arm/kernel/irq.c
+++ b/arch/arm/kernel/irq.c
@@ -175,7 +175,7 @@  static bool migrate_one_irq(struct irq_desc *desc)
 	c = irq_data_get_irq_chip(d);
 	if (!c->irq_set_affinity)
 		pr_debug("IRQ%u: unable to set affinity\n", d->irq);
-	else if (c->irq_set_affinity(d, affinity, true) == IRQ_SET_MASK_OK && ret)
+	else if (c->irq_set_affinity(d, affinity, false) == IRQ_SET_MASK_OK && ret)
 		cpumask_copy(d->affinity, affinity);
 
 	return ret;