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 <vincent.whitchurch@axis.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230613-genirq-nested-v3-1-ae58221143eb@axis.com

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index bdd35bb9c735..831f38308466 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);