From e2c12739ccf76aae12e9e949526a475b9d17adaa Mon Sep 17 00:00:00 2001 From: Vincent Whitchurch Date: Thu, 6 Jul 2023 16:22:25 +0200 Subject: [PATCH] genirq: Prevent nested thread vs synchronize_hardirq() deadlock There is a possibility of deadlock if synchronize_hardirq() is called when the nested threaded interrupt is active. The following scenario was observed on a uniprocessor PREEMPT_NONE system: Thread 1 Thread 2 handle_nested_thread() Set INPROGRESS Call ->thread_fn() thread_fn goes to sleep free_irq() __synchronize_hardirq() Busy-loop forever waiting for INPROGRESS to be cleared The INPROGRESS flag is only supposed to be used for hard interrupt handlers. Remove the incorrect usage in the nested threaded interrupt case and instead re-use the threads_active / wait_for_threads mechanism to wait for nested threaded interrupts to complete. Signed-off-by: Vincent Whitchurch Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20230613-genirq-nested-v3-1-ae58221143eb@axis.com --- kernel/irq/chip.c | 11 ++++------- kernel/irq/internals.h | 2 ++ kernel/irq/manage.c | 26 ++++++++++++++------------ 3 files changed, 20 insertions(+), 19 deletions(-) diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c index ee8c0acf39df19..dc94e0bf2c9408 100644 --- a/kernel/irq/chip.c +++ b/kernel/irq/chip.c @@ -473,11 +473,12 @@ void handle_nested_irq(unsigned int irq) action = desc->action; if (unlikely(!action || irqd_irq_disabled(&desc->irq_data))) { desc->istate |= IRQS_PENDING; - goto out_unlock; + raw_spin_unlock_irq(&desc->lock); + return; } kstat_incr_irqs_this_cpu(desc); - irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS); + atomic_inc(&desc->threads_active); raw_spin_unlock_irq(&desc->lock); action_ret = IRQ_NONE; @@ -487,11 +488,7 @@ void handle_nested_irq(unsigned int irq) if (!irq_settings_no_debug(desc)) note_interrupt(desc, action_ret); - raw_spin_lock_irq(&desc->lock); - irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS); - -out_unlock: - raw_spin_unlock_irq(&desc->lock); + wake_threads_waitq(desc); } EXPORT_SYMBOL_GPL(handle_nested_irq); diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h index bdd35bb9c7357c..831f383084663b 100644 --- a/kernel/irq/internals.h +++ b/kernel/irq/internals.h @@ -121,6 +121,8 @@ void irq_resend_init(struct irq_desc *desc); bool irq_wait_for_poll(struct irq_desc *desc); void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action); +void wake_threads_waitq(struct irq_desc *desc); + #ifdef CONFIG_PROC_FS extern void register_irq_proc(unsigned int irq, struct irq_desc *desc); extern void unregister_irq_proc(unsigned int irq, struct irq_desc *desc); diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index d2742af0f0fd87..d309ba84e08a9d 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -108,6 +108,16 @@ bool synchronize_hardirq(unsigned int irq) } EXPORT_SYMBOL(synchronize_hardirq); +static void __synchronize_irq(struct irq_desc *desc) +{ + __synchronize_hardirq(desc, true); + /* + * We made sure that no hardirq handler is running. Now verify that no + * threaded handlers are active. + */ + wait_event(desc->wait_for_threads, !atomic_read(&desc->threads_active)); +} + /** * synchronize_irq - wait for pending IRQ handlers (on other CPUs) * @irq: interrupt number to wait for @@ -127,16 +137,8 @@ void synchronize_irq(unsigned int irq) { struct irq_desc *desc = irq_to_desc(irq); - if (desc) { - __synchronize_hardirq(desc, true); - /* - * We made sure that no hardirq handler is - * running. Now verify that no threaded handlers are - * active. - */ - wait_event(desc->wait_for_threads, - !atomic_read(&desc->threads_active)); - } + if (desc) + __synchronize_irq(desc); } EXPORT_SYMBOL(synchronize_irq); @@ -1216,7 +1218,7 @@ static irqreturn_t irq_thread_fn(struct irq_desc *desc, return ret; } -static void wake_threads_waitq(struct irq_desc *desc) +void wake_threads_waitq(struct irq_desc *desc) { if (atomic_dec_and_test(&desc->threads_active)) wake_up(&desc->wait_for_threads); @@ -1944,7 +1946,7 @@ static struct irqaction *__free_irq(struct irq_desc *desc, void *dev_id) * supports it also make sure that there is no (not yet serviced) * interrupt in flight at the hardware level. */ - __synchronize_hardirq(desc, true); + __synchronize_irq(desc); #ifdef CONFIG_DEBUG_SHIRQ /*