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Subject[tip:irq/urgent] genirq: Add mutex to irq desc to serialize request/free_irq()
Commit-ID:  9114014cf4e6df0b22d764380ae1fc54f1a7a8b2
Gitweb: http://git.kernel.org/tip/9114014cf4e6df0b22d764380ae1fc54f1a7a8b2
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Thu, 29 Jun 2017 23:33:37 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 4 Jul 2017 12:46:16 +0200

genirq: Add mutex to irq desc to serialize request/free_irq()

The irq_request/release_resources() callbacks ar currently invoked under
desc->lock with interrupts disabled. This is a source of problems on RT and
conceptually not required.

Add a seperate mutex to struct irq_desc which allows to serialize
request/free_irq(), which can be used to move the resource functions out of
the desc->lock held region.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Julia Cartwright <julia@ni.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Brian Norris <briannorris@chromium.org>
Cc: Doug Anderson <dianders@chromium.org>
Cc: linux-rockchip@lists.infradead.org
Cc: John Keeping <john@metanate.com>
Cc: linux-gpio@vger.kernel.org
Link: http://lkml.kernel.org/r/20170629214344.039220922@linutronix.de

---
include/linux/irqdesc.h | 3 +++
kernel/irq/irqdesc.c | 1 +
kernel/irq/manage.c | 8 ++++++++
3 files changed, 12 insertions(+)

diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index d425a3a..3e90a09 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -3,6 +3,7 @@

#include <linux/rcupdate.h>
#include <linux/kobject.h>
+#include <linux/mutex.h>

/*
* Core internal functions to deal with irq descriptors
@@ -45,6 +46,7 @@ struct pt_regs;
* IRQF_FORCE_RESUME set
* @rcu: rcu head for delayed free
* @kobj: kobject used to represent this struct in sysfs
+ * @request_mutex: mutex to protect request/free before locking desc->lock
* @dir: /proc/irq/ procfs entry
* @debugfs_file: dentry for the debugfs file
* @name: flow handler name for /proc/interrupts output
@@ -96,6 +98,7 @@ struct irq_desc {
struct rcu_head rcu;
struct kobject kobj;
#endif
+ struct mutex request_mutex;
int parent_irq;
struct module *owner;
const char *name;
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 948b50e..906a67e 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -373,6 +373,7 @@ static struct irq_desc *alloc_desc(int irq, int node, unsigned int flags,

raw_spin_lock_init(&desc->lock);
lockdep_set_class(&desc->lock, &irq_desc_lock_class);
+ mutex_init(&desc->request_mutex);
init_rcu_head(&desc->rcu);

desc_set_defaults(irq, desc, node, affinity, owner);
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 0934e02..0139908 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1167,6 +1167,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
if (desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)
new->flags &= ~IRQF_ONESHOT;

+ mutex_lock(&desc->request_mutex);
+
chip_bus_lock(desc);

/*
@@ -1350,6 +1352,7 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)

raw_spin_unlock_irqrestore(&desc->lock, flags);
chip_bus_sync_unlock(desc);
+ mutex_unlock(&desc->request_mutex);

irq_setup_timings(desc, new);

@@ -1383,6 +1386,8 @@ out_unlock:

chip_bus_sync_unlock(desc);

+ mutex_unlock(&desc->request_mutex);
+
out_thread:
if (new->thread) {
struct task_struct *t = new->thread;
@@ -1446,6 +1451,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
if (!desc)
return NULL;

+ mutex_lock(&desc->request_mutex);
chip_bus_lock(desc);
raw_spin_lock_irqsave(&desc->lock, flags);

@@ -1521,6 +1527,8 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
}
}

+ mutex_unlock(&desc->request_mutex);
+
irq_chip_pm_put(&desc->irq_data);
module_put(desc->owner);
kfree(action->secondary);
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