From 788019eb559fd0b365f501467ceafce540e377cc Mon Sep 17 00:00:00 2001 From: Brian Norris Date: Wed, 14 May 2025 13:13:16 -0700 Subject: [PATCH] genirq: Retain disable depth for managed interrupts across CPU hotplug Affinity-managed interrupts can be shut down and restarted during CPU hotunplug/plug. Thereby the interrupt may be left in an unexpected state. Specifically: 1. Interrupt is affine 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! driver expects that the interrupt still disabled) 7. enable_irq() -> depth underflow / unbalanced enable_irq() warning This is only a problem for managed interrupts and CPU hotplug, all other cases like request()/free()/request() truly needs to reset a possibly stale disable depth value. Provide a startup function, which takes the disable depth into account, and invoked it for the managed interrupts in the CPU hotplug path. This requires to change irq_shutdown() to do a depth increment instead of setting it to 1, which allows to retain the disable depth, but is harmless for the other code paths using irq_startup(), which will still reset the disable depth unconditionally to keep the original correct behaviour. A kunit tests will be added separately to cover some of these aspects. [ tglx: Massaged changelog ] Suggested-by: Thomas Gleixner Signed-off-by: Brian Norris Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250514201353.3481400-2-briannorris@chromium.org --- kernel/irq/chip.c | 22 +++++++++++++++++++++- kernel/irq/cpuhotplug.c | 2 +- kernel/irq/internals.h | 1 + 3 files changed, 23 insertions(+), 2 deletions(-) diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c index 1d45c84d7356b..b0e0a7332993c 100644 --- a/kernel/irq/chip.c +++ b/kernel/irq/chip.c @@ -202,6 +202,19 @@ __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, @@ -269,6 +282,7 @@ 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; } @@ -301,7 +315,13 @@ 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); diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c index e77ca6db5e11e..f07529ae48952 100644 --- a/kernel/irq/cpuhotplug.c +++ b/kernel/irq/cpuhotplug.c @@ -218,7 +218,7 @@ 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 diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h index 476a20fd9bfce..aebfe225c9a6d 100644 --- a/kernel/irq/internals.h +++ b/kernel/irq/internals.h @@ -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); -- 2.47.2