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FROMGIT: genirq: Retain depth for managed IRQs across CPU hotplug

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Affinity-managed IRQs may be shut down and restarted during CPU
hotunplug/plug, and the IRQ may be left in an unexpected state.
Specifically:

 1. IRQ affines to CPU N
 2. disable_irq() -> depth is 1
 3. CPU N goes offline
 4. irq_shutdown() -> depth is set to 1 (again)
 5. CPU N goes online
 6. irq_startup() -> depth is set to 0 (BUG! client expected IRQ is
    still disabled)
 7. enable_irq() -> depth underflow / unbalanced enable_irq() WARN

It seems depth only needs preserved for managed IRQs + CPU hotplug, so
per Thomas's recommendation, we make that explicit.

I add kunit tests that cover some of this in a following patch.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Co-developed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250514201353.3481400-2-briannorris@chromium.org
Bug: 417330473
Change-Id: I9e19d182b0c16f353aa9068cac4eff8a64ffb21b
(cherry picked from commit 788019eb559fd0b365f501467ceafce540e377cc git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git)
Signed-off-by: Bart Van Assche <bvanassche@google.com>
This commit is contained in:
Brian Norris
2025-05-14 13:13:16 -07:00
committed by Sandeep Dhavale
parent 1bc40b53aa
commit 65ad590076
3 changed files with 23 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
kernel/irq/chip.c
View File

@@ -224,6 +224,19 @@ __irq_startup_managed(struct irq_desc *desc, const struct cpumask *aff,
return IRQ_STARTUP_ABORT;
return IRQ_STARTUP_MANAGED;
}
void irq_startup_managed(struct irq_desc *desc)
{
/*
* Only start it up when the disable depth is 1, so that a disable,
* hotunplug, hotplug sequence does not end up enabling it during
* hotplug unconditionally.
*/
desc->depth--;
if (!desc->depth)
irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
}
#else
static __always_inline int
__irq_startup_managed(struct irq_desc *desc, const struct cpumask *aff,
@@ -276,6 +289,7 @@ int irq_startup(struct irq_desc *desc, bool resend, bool force)
ret = __irq_startup(desc);
break;
case IRQ_STARTUP_ABORT:
desc->depth = 1;
irqd_set_managed_shutdown(d);
return 0;
}
@@ -308,7 +322,13 @@ void irq_shutdown(struct irq_desc *desc)
{
if (irqd_is_started(&desc->irq_data)) {
clear_irq_resend(desc);
desc->depth = 1;
/*
* Increment disable depth, so that a managed shutdown on
* CPU hotunplug preserves the actual disabled state when the
* CPU comes back online. See irq_startup_managed().
*/
desc->depth++;
if (desc->irq_data.chip->irq_shutdown) {
desc->irq_data.chip->irq_shutdown(&desc->irq_data);
irq_state_set_disabled(desc);

2
kernel/irq/cpuhotplug.c
View File

@@ -219,7 +219,7 @@ static void irq_restore_affinity_of_irq(struct irq_desc *desc, unsigned int cpu)
return;
if (irqd_is_managed_and_shutdown(data))
irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
irq_startup_managed(desc);
/*
* If the interrupt can only be directed to a single target

1
kernel/irq/internals.h
View File

@@ -87,6 +87,7 @@ extern void __enable_irq(struct irq_desc *desc);
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_startup_managed(struct irq_desc *desc);
extern void irq_shutdown(struct irq_desc *desc);
extern void irq_shutdown_and_deactivate(struct irq_desc *desc);