genirq: Add return value to check_irq_resend()

In preparation for an interrupt injection interface which can be used
safely by error injection mechanisms. e.g. PCI-E/ AER, add a return value
to check_irq_resend() so errors can be propagated to the caller.

Split out the software resend code so the ugly #ifdef in check_irq_resend()
goes away and the whole thing becomes readable.

Fix up the caller in debugfs. The caller in irq_startup() does not care
about the return value as this is unconditionally invoked for all
interrupts and the resend is best effort anyway.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lkml.kernel.org/r/20200306130623.775200917@linutronix.de

kernel/irq/debugfs.c

@@ -218,8 +218,7 @@ static ssize_t irq_debug_write(struct file *file, const char __user *user_buf,
 			err = -EINVAL;
 		} else {
 			desc->istate |= IRQS_PENDING;
-			check_irq_resend(desc);
-			err = 0;
+			err = check_irq_resend(desc);
 		}
 
 		raw_spin_unlock_irqrestore(&desc->lock, flags);

kernel/irq/internals.h

@@ -108,7 +108,7 @@ irqreturn_t handle_irq_event_percpu(struct irq_desc *desc);
 irqreturn_t handle_irq_event(struct irq_desc *desc);
 
 /* Resending of interrupts :*/
-void check_irq_resend(struct irq_desc *desc);
+int check_irq_resend(struct irq_desc *desc);
 bool irq_wait_for_poll(struct irq_desc *desc);
 void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action);
 

kernel/irq/resend.c

@@ -47,57 +47,72 @@ static void resend_irqs(unsigned long arg)
 /* Tasklet to handle resend: */
 static DECLARE_TASKLET(resend_tasklet, resend_irqs, 0);
 
-#endif
-
-/*
- * IRQ resend
- *
- * Is called with interrupts disabled and desc->lock held.
- */
-void check_irq_resend(struct irq_desc *desc)
+static int irq_sw_resend(struct irq_desc *desc)
 {
+	unsigned int irq = irq_desc_get_irq(desc);
+
 	/*
-	 * We do not resend level type interrupts. Level type
-	 * interrupts are resent by hardware when they are still
-	 * active. Clear the pending bit so suspend/resume does not
-	 * get confused.
+	 * Validate whether this interrupt can be safely injected from
+	 * non interrupt context
 	 */
-	if (irq_settings_is_level(desc)) {
-		desc->istate &= ~IRQS_PENDING;
-		return;
-	}
-	if (desc->istate & IRQS_REPLAY)
-		return;
-	if (desc->istate & IRQS_PENDING) {
-		desc->istate &= ~IRQS_PENDING;
-		desc->istate |= IRQS_REPLAY;
-
-		if ((!desc->irq_data.chip->irq_retrigger ||
-		    !desc->irq_data.chip->irq_retrigger(&desc->irq_data)) &&
-		    !handle_enforce_irqctx(&desc->irq_data)) {
-#ifdef CONFIG_HARDIRQS_SW_RESEND
-			unsigned int irq = irq_desc_get_irq(desc);
+	if (handle_enforce_irqctx(&desc->irq_data))
+		return -EINVAL;
 
 	/*
-			 * If the interrupt is running in the thread
-			 * context of the parent irq we need to be
-			 * careful, because we cannot trigger it
+	 * If the interrupt is running in the thread context of the parent
+	 * irq we need to be careful, because we cannot trigger it
 	 * directly.
 	 */
 	if (irq_settings_is_nested_thread(desc)) {
 		/*
-				 * If the parent_irq is valid, we
-				 * retrigger the parent, otherwise we
-				 * do nothing.
+		 * If the parent_irq is valid, we retrigger the parent,
+		 * otherwise we do nothing.
 		 */
 		if (!desc->parent_irq)
-					return;
+			return -EINVAL;
 		irq = desc->parent_irq;
 	}
+
 	/* Set it pending and activate the softirq: */
 	set_bit(irq, irqs_resend);
 	tasklet_schedule(&resend_tasklet);
+	return 0;
+}
+
+#else
+static int irq_sw_resend(struct irq_desc *desc)
+{
+	return -EINVAL;
+}
 #endif
+
+/*
+ * IRQ resend
+ *
+ * Is called with interrupts disabled and desc->lock held.
+ */
+int check_irq_resend(struct irq_desc *desc)
+{
+	/*
+	 * We do not resend level type interrupts. Level type interrupts
+	 * are resent by hardware when they are still active. Clear the
+	 * pending bit so suspend/resume does not get confused.
+	 */
+	if (irq_settings_is_level(desc)) {
+		desc->istate &= ~IRQS_PENDING;
+		return -EINVAL;
 	}
+
+	if (desc->istate & IRQS_REPLAY)
+		return -EBUSY;
+
+	if (desc->istate & IRQS_PENDING) {
+		desc->istate &= ~IRQS_PENDING;
+		desc->istate |= IRQS_REPLAY;
+
+		if (!desc->irq_data.chip->irq_retrigger ||
+		    !desc->irq_data.chip->irq_retrigger(&desc->irq_data))
+		    return irq_sw_resend(desc);
 	}
+	return 0;
 }