genirq: Add might_sleep() to disable_irq()

With the introduction of threaded interrupt handlers, it is virtually
never safe to call disable_irq() from non-premptible context.

Thus: Update the documentation, add an explicit might_sleep() to catch any
offenders. This is more obvious and straight forward than the implicit
might_sleep() check deeper down in the disable_irq() call chain.

Fixes: 3aa551c9b4c4 ("genirq: add threaded interrupt handler support")
Signed-off-by: Manfred Spraul <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

kernel/irq/manage.c

···
  *	to complete before returning. If you use this function while
  *	holding a resource the IRQ handler may need you will deadlock.
  *
- *	This function may be called - with care - from IRQ context.
+ *	Can only be called from preemptible code as it might sleep when
+ *	an interrupt thread is associated to @irq.
+ *
  */
 void disable_irq(unsigned int irq)
 {
+	might_sleep();
 	if (!__disable_irq_nosync(irq))
 		synchronize_irq(irq);
 }