genirq/cpuhotplug: Restore affinity even for suspended IRQ

Commit 788019eb559f ("genirq: Retain disable depth for managed interrupts
across CPU hotplug") tried to make managed shutdown/startup properly
reference counted, but it missed the fact that the unplug and hotplug code
has an intentional imbalance by skipping IRQS_SUSPENDED interrupts on
the "restore" path.

This means that if a managed-affinity interrupt was both suspended and
managed-shutdown (such as may happen during system suspend / S3), resume
skips calling irq_startup_managed(), and would again have an unbalanced
depth this time, with a positive value (i.e., remaining unexpectedly
masked).

This IRQS_SUSPENDED check was introduced in commit a60dd06af674
("genirq/cpuhotplug: Skip suspended interrupts when restoring affinity")
for essentially the same reason as commit 788019eb559f, to prevent that
irq_startup() would unconditionally re-enable an interrupt too early.

Because irq_startup_managed() now respsects the disable-depth count, the
IRQS_SUSPENDED check is not longer needed, and instead, it causes harm.

Thus, drop the IRQS_SUSPENDED check, and restore balance.

This effectively reverts commit a60dd06af674 ("genirq/cpuhotplug: Skip
suspended interrupts when restoring affinity"), because it is replaced
by commit 788019eb559f ("genirq: Retain disable depth for managed
interrupts across CPU hotplug").

Fixes: 788019eb559f ("genirq: Retain disable depth for managed interrupts across CPU hotplug")
Reported-by: Aleksandrs Vinarskis <alex.vinarskis@gmail.com>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Aleksandrs Vinarskis <alex.vinarskis@gmail.com>
Link: https://lore.kernel.org/all/20250612183303.3433234-3-briannorris@chromium.org
Closes: https://lore.kernel.org/lkml/24ec4adc-7c80-49e9-93ee-19908a97ab84@gmail.com/

diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index f07529ae489527423b2e758ce61e7f51c46a1013..755346ea98196747f690aba2f1a39af9b0b9a16f 100644 (file)
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -210,13 +210,6 @@ static void irq_restore_affinity_of_irq(struct irq_desc *desc, unsigned int cpu)
            !irq_data_get_irq_chip(data) || !cpumask_test_cpu(cpu, affinity))
                return;
 
-       /*
-        * Don't restore suspended interrupts here when a system comes back
-        * from S3. They are reenabled via resume_device_irqs().
-        */
-       if (desc->istate & IRQS_SUSPENDED)
-               return;
-
        if (irqd_is_managed_and_shutdown(data))
                irq_startup_managed(desc);