linux-kernel - [tip:irq/urgent] genirq: Move irq resource handling out of spinlocked region

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Date:   Tue, 4 Jul 2017 03:49:18 -0700
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, dianders@...omium.org,
        briannorris@...omium.org, marc.zyngier@....com, tglx@...utronix.de,
        john@...anate.com, mingo@...nel.org, hpa@...or.com,
        linus.walleij@...aro.org, julia@...com, heiko@...ech.de
Subject: [tip:irq/urgent] genirq: Move irq resource handling out of
 spinlocked region

Commit-ID:  46e48e257360f0845fe17089713cbad4db611e70
Gitweb:     http://git.kernel.org/tip/46e48e257360f0845fe17089713cbad4db611e70
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Thu, 29 Jun 2017 23:33:38 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 4 Jul 2017 12:46:16 +0200

genirq: Move irq resource handling out of spinlocked region

Aside of being conceptually wrong, there is also an actual (hard to
trigger and mostly theoretical) problem.

CPU0				CPU1
free_irq(X)			interrupt X
				spin_lock(desc->lock)
				wake irq thread()
				spin_unlock(desc->lock)
spin_lock(desc->lock)
remove action()
shutdown_irq()			
release_resources()		thread_handler()
spin_unlock(desc->lock)		  access released resources.

synchronize_irq()

Move the release resources invocation after synchronize_irq() so it's
guaranteed that the threaded handler has finished.

Move the resource request call out of the desc->lock held region as well,
so the invocation context is the same for both request and release.

This solves the problems with those functions on RT as well.
 
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Marc Zyngier <marc.zyngier@....com>
Cc: Heiko Stuebner <heiko@...ech.de>
Cc: Julia Cartwright <julia@...com>
Cc: Linus Walleij <linus.walleij@...aro.org>
Cc: Brian Norris <briannorris@...omium.org>
Cc: Doug Anderson <dianders@...omium.org>
Cc: linux-rockchip@...ts.infradead.org
Cc: John Keeping <john@...anate.com>
Cc: linux-gpio@...r.kernel.org
Link: http://lkml.kernel.org/r/20170629214344.117028181@linutronix.de

---
 kernel/irq/manage.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 0139908..3e69343 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1168,6 +1168,14 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		new->flags &= ~IRQF_ONESHOT;
 
 	mutex_lock(&desc->request_mutex);
+	if (!desc->action) {
+		ret = irq_request_resources(desc);
+		if (ret) {
+			pr_err("Failed to request resources for %s (irq %d) on irqchip %s\n",
+			       new->name, irq, desc->irq_data.chip->name);
+			goto out_mutex;
+		}
+	}
 
 	chip_bus_lock(desc);
 
@@ -1271,13 +1279,6 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 	}
 
 	if (!shared) {
-		ret = irq_request_resources(desc);
-		if (ret) {
-			pr_err("Failed to request resources for %s (irq %d) on irqchip %s\n",
-			       new->name, irq, desc->irq_data.chip->name);
-			goto out_unlock;
-		}
-
 		init_waitqueue_head(&desc->wait_for_threads);
 
 		/* Setup the type (level, edge polarity) if configured: */
@@ -1386,6 +1387,10 @@ out_unlock:
 
 	chip_bus_sync_unlock(desc);
 
+	if (!desc->action)
+		irq_release_resources(desc);
+
+out_mutex:
 	mutex_unlock(&desc->request_mutex);
 
 out_thread:
@@ -1484,7 +1489,6 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 	if (!desc->action) {
 		irq_settings_clr_disable_unlazy(desc);
 		irq_shutdown(desc);
-		irq_release_resources(desc);
 		irq_remove_timings(desc);
 	}
 
@@ -1527,6 +1531,9 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 		}
 	}
 
+	if (!desc->action)
+		irq_release_resources(desc);
+
 	mutex_unlock(&desc->request_mutex);
 
 	irq_chip_pm_put(&desc->irq_data);