linux-kernel - [tip:irq/core] genirq: Warn when IRQ_NOAUTOEN is used with shared interrupts

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Date:   Sun, 4 Jun 2017 05:48:27 -0700
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     marc.zyngier@....com, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, jeffy.chen@...k-chips.com,
        hpa@...or.com, mingo@...nel.org, briannorris@...omium.org
Subject: [tip:irq/core] genirq: Warn when IRQ_NOAUTOEN is used with shared
 interrupts

Commit-ID:  04c848d398797a626608ff48804d809ae6687163
Gitweb:     http://git.kernel.org/tip/04c848d398797a626608ff48804d809ae6687163
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Wed, 31 May 2017 11:58:33 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sun, 4 Jun 2017 14:38:41 +0200

genirq: Warn when IRQ_NOAUTOEN is used with shared interrupts

Shared interrupts do not go well with disabling auto enable:

1) The sharing interrupt might request it while it's still disabled and
   then wait for interrupts forever.

2) The interrupt might have been requested by the driver sharing the line
   before IRQ_NOAUTOEN has been set. So the driver which expects that
   disabled state after calling request_irq() will not get what it wants.
   Even worse, when it calls enable_irq() later, it will trigger the
   unbalanced enable_irq() warning.

Reported-by: Brian Norris <briannorris@...omium.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: dianders@...omium.org
Cc: jeffy <jeffy.chen@...k-chips.com>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: tfiga@...omium.org
Link: http://lkml.kernel.org/r/20170531100212.210682135@linutronix.de
---
 kernel/irq/chip.c   |  7 +++++++
 kernel/irq/manage.c | 12 ++++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index e0051d5..bc1331f 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -935,6 +935,13 @@ void irq_modify_status(unsigned int irq, unsigned long clr, unsigned long set)
 
 	if (!desc)
 		return;
+
+	/*
+	 * Warn when a driver sets the no autoenable flag on an already
+	 * active interrupt.
+	 */
+	WARN_ON_ONCE(!desc->depth && (set & _IRQ_NOAUTOEN));
+
 	irq_settings_clr_and_set(desc, clr, set);
 
 	irqd_clear(&desc->irq_data, IRQD_NO_BALANCING | IRQD_PER_CPU |
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 5705610..49c37f1 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1334,11 +1334,19 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		if (new->flags & IRQF_ONESHOT)
 			desc->istate |= IRQS_ONESHOT;
 
-		if (irq_settings_can_autoenable(desc))
+		if (irq_settings_can_autoenable(desc)) {
 			irq_startup(desc, true);
-		else
+		} else {
+			/*
+			 * Shared interrupts do not go well with disabling
+			 * auto enable. The sharing interrupt might request
+			 * it while it's still disabled and then wait for
+			 * interrupts forever.
+			 */
+			WARN_ON_ONCE(new->flags & IRQF_SHARED);
 			/* Undo nested disables: */
 			desc->depth = 1;
+		}
 
 		/* Exclude IRQ from balancing if requested */
 		if (new->flags & IRQF_NOBALANCING) {