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SubjectRe: [patch 1/5] genirq: Delay deactivation in free_irq()
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Hi Thomas,

On 25/06/2019 12:13, Thomas Gleixner wrote:
> When interrupts are shutdown, they are immediately deactivated in the
> irqdomain hierarchy. While this looks obviously correct there is a subtle
> issue:
>
> There might be an interrupt in flight when free_irq() is invoking the
> shutdown. This is properly handled at the irq descriptor / primary handler
> level, but the deactivation might completely disable resources which are
> required to acknowledge the interrupt.
>
> Split the shutdown code and deactivate the interrupt after synchronization
> in free_irq(). Fixup all other usage sites where this is not an issue to
> invoke the combined shutdown_and_deactivate() function instead.
>
> This still might be an issue if the interrupt in flight servicing is
> delayed on a remote CPU beyond the invocation of synchronize_irq(), but
> that cannot be handled at that level and needs to be handled in the
> synchronize_irq() context.
>
> Fixes: f8264e34965a ("irqdomain: Introduce new interfaces to support hierarchy irqdomains")
> Reported-by: Robert Hodaszi <Robert.Hodaszi@digi.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> kernel/irq/autoprobe.c | 6 +++---
> kernel/irq/chip.c | 6 ++++++
> kernel/irq/cpuhotplug.c | 2 +-
> kernel/irq/internals.h | 1 +
> kernel/irq/manage.c | 12 +++++++++++-
> 5 files changed, 22 insertions(+), 5 deletions(-)
>
> --- a/kernel/irq/autoprobe.c
> +++ b/kernel/irq/autoprobe.c
> @@ -90,7 +90,7 @@ unsigned long probe_irq_on(void)
> /* It triggered already - consider it spurious. */
> if (!(desc->istate & IRQS_WAITING)) {
> desc->istate &= ~IRQS_AUTODETECT;
> - irq_shutdown(desc);
> + irq_shutdown_and_deactivate(desc);
> } else
> if (i < 32)
> mask |= 1 << i;
> @@ -127,7 +127,7 @@ unsigned int probe_irq_mask(unsigned lon
> mask |= 1 << i;
>
> desc->istate &= ~IRQS_AUTODETECT;
> - irq_shutdown(desc);
> + irq_shutdown_and_deactivate(desc);
> }
> raw_spin_unlock_irq(&desc->lock);
> }
> @@ -169,7 +169,7 @@ int probe_irq_off(unsigned long val)
> nr_of_irqs++;
> }
> desc->istate &= ~IRQS_AUTODETECT;
> - irq_shutdown(desc);
> + irq_shutdown_and_deactivate(desc);
> }
> raw_spin_unlock_irq(&desc->lock);
> }
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -314,6 +314,12 @@ void irq_shutdown(struct irq_desc *desc)
> }
> irq_state_clr_started(desc);
> }
> +}
> +
> +
> +void irq_shutdown_and_deactivate(struct irq_desc *desc)
> +{
> + irq_shutdown(desc);
> /*
> * This must be called even if the interrupt was never started up,
> * because the activation can happen before the interrupt is
> --- a/kernel/irq/cpuhotplug.c
> +++ b/kernel/irq/cpuhotplug.c
> @@ -116,7 +116,7 @@ static bool migrate_one_irq(struct irq_d
> */
> if (irqd_affinity_is_managed(d)) {
> irqd_set_managed_shutdown(d);
> - irq_shutdown(desc);
> + irq_shutdown_and_deactivate(desc);
> return false;
> }
> affinity = cpu_online_mask;
> --- a/kernel/irq/internals.h
> +++ b/kernel/irq/internals.h
> @@ -82,6 +82,7 @@ extern int irq_activate_and_startup(stru
> extern int irq_startup(struct irq_desc *desc, bool resend, bool force);
>
> extern void irq_shutdown(struct irq_desc *desc);
> +extern void irq_shutdown_and_deactivate(struct irq_desc *desc);
> extern void irq_enable(struct irq_desc *desc);
> extern void irq_disable(struct irq_desc *desc);
> extern void irq_percpu_enable(struct irq_desc *desc, unsigned int cpu);
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -13,6 +13,7 @@
> #include <linux/module.h>
> #include <linux/random.h>
> #include <linux/interrupt.h>
> +#include <linux/irqdomain.h>
> #include <linux/slab.h>
> #include <linux/sched.h>
> #include <linux/sched/rt.h>
> @@ -1699,6 +1700,7 @@ static struct irqaction *__free_irq(stru
> /* If this was the last handler, shut down the IRQ line: */
> if (!desc->action) {
> irq_settings_clr_disable_unlazy(desc);
> + /* Only shutdown. Deactivate after synchronize_irq() */

synchronize_hardirq()

> irq_shutdown(desc);
> }
>
> @@ -1768,6 +1770,14 @@ static struct irqaction *__free_irq(stru
> * require it to deallocate resources over the slow bus.
> */
> chip_bus_lock(desc);
> + /*
> + * There is no interrupt on the fly anymore. Deactivate it
> + * completely.
> + */
> + raw_spin_lock_irqsave(&desc->lock, flags);
> + irq_domain_deactivate_irq(&desc->irq_data);
> + raw_spin_unlock_irqrestore(&desc->lock, flags);
> +
> irq_release_resources(desc);
> chip_bus_sync_unlock(desc);
> irq_remove_timings(desc);
> @@ -1855,7 +1865,7 @@ static const void *__cleanup_nmi(unsigne
> }
>
> irq_settings_clr_disable_unlazy(desc);
> - irq_shutdown(desc);
> + irq_shutdown_and_deactivate(desc);
>
> irq_release_resources(desc);
The patch makes complete sense, so this comment is only a nit, feel free
to ignore me: I find it a bit odd that irq_shutdown() doesn't do the
full thing anymore, given that it is the "canonical" function, and that
__free_irq is the only one that has special needs. Suggestion below.

Irrespective of which version you prefer:

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

M.

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 29d6c7d070b4..aeab853fcc10 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -301,7 +301,7 @@ int irq_activate_and_startup(struct irq_desc *desc, bool resend)

static void __irq_disable(struct irq_desc *desc, bool mask);

-void irq_shutdown(struct irq_desc *desc)
+void __irq_shutdown(struct irq_desc *desc)
{
if (irqd_is_started(&desc->irq_data)) {
desc->depth = 1;
@@ -314,6 +314,11 @@ void irq_shutdown(struct irq_desc *desc)
}
irq_state_clr_started(desc);
}
+}
+
+void irq_shutdown(struct irq_desc *desc)
+{
+ __irq_shutdown(desc);
/*
* This must be called even if the interrupt was never started up,
* because the activation can happen before the interrupt is
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 70c3053bc1f6..107f7d342e3d 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -81,6 +81,7 @@ extern int irq_activate(struct irq_desc *desc);
extern int irq_activate_and_startup(struct irq_desc *desc, bool resend);
extern int irq_startup(struct irq_desc *desc, bool resend, bool force);

+extern void __irq_shutdown(struct irq_desc *desc);
extern void irq_shutdown(struct irq_desc *desc);
extern void irq_enable(struct irq_desc *desc);
extern void irq_disable(struct irq_desc *desc);
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 78f3ddeb7fe4..f19e3589989e 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -13,6 +13,7 @@
#include <linux/module.h>
#include <linux/random.h>
#include <linux/interrupt.h>
+#include <linux/irqdomain.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/sched/rt.h>
@@ -1699,7 +1700,8 @@ static struct irqaction *__free_irq(struct irq_desc *desc, void *dev_id)
/* If this was the last handler, shut down the IRQ line: */
if (!desc->action) {
irq_settings_clr_disable_unlazy(desc);
- irq_shutdown(desc);
+ /* Only shutdown. Deactivate after synchronize_hardirq() */
+ __irq_shutdown(desc);
}

#ifdef CONFIG_SMP
@@ -1768,6 +1770,14 @@ static struct irqaction *__free_irq(struct irq_desc *desc, void *dev_id)
* require it to deallocate resources over the slow bus.
*/
chip_bus_lock(desc);
+ /*
+ * There is no interrupt on the fly anymore. Deactivate it
+ * completely.
+ */
+ raw_spin_lock_irqsave(&desc->lock, flags);
+ irq_domain_deactivate_irq(&desc->irq_data);
+ raw_spin_unlock_irqrestore(&desc->lock, flags);
+
irq_release_resources(desc);
chip_bus_sync_unlock(desc);
irq_remove_timings(desc);
--
Jazz is not dead. It just smells funny...

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