[patch V2 02/31] genirq/msi: Add mutex for MSI list protection

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

For upcoming runtime extensions of MSI-X interrupts it's required to
protect the MSI descriptor list. Add a mutex to struct msi_device_data and
provide lock/unlock functions.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 include/linux/msi.h |    5 +++++
 kernel/irq/msi.c    |   25 +++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -3,6 +3,7 @@
 #define LINUX_MSI_H
 
 #include <linux/cpumask.h>
+#include <linux/mutex.h>
 #include <linux/list.h>
 #include <linux/bits.h>
 #include <asm/msi.h>
@@ -146,12 +147,14 @@ struct msi_desc {
  * @attrs:             Pointer to the sysfs attribute group
  * @platform_data:     Platform-MSI specific data
  * @list:              List of MSI descriptors associated to the device
+ * @mutex:             Mutex protecting the MSI list
  */
 struct msi_device_data {
        unsigned long                   properties;
        const struct attribute_group    **attrs;
        struct platform_msi_priv_data   *platform_data;
        struct list_head                list;
+       struct mutex                    mutex;
 };
 
 int msi_setup_device_data(struct device *dev);
@@ -173,6 +176,8 @@ static inline void msi_device_set_proper
 #endif
 
 unsigned int msi_get_virq(struct device *dev, unsigned int index);
+void msi_lock_descs(struct device *dev);
+void msi_unlock_descs(struct device *dev);
 
 /* Helpers to hide struct msi_desc implementation details */
 #define msi_desc_to_dev(desc)          ((desc)->dev)
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -127,12 +127,37 @@ int msi_setup_device_data(struct device
                return -ENOMEM;
 
        INIT_LIST_HEAD(&md->list);
+       mutex_init(&md->mutex);
        dev->msi.data = md;
        devres_add(dev, md);
        return 0;
 }
 
 /**
+ * msi_lock_descs - Lock the MSI descriptor storage of a device
+ * @dev:       Device to operate on
+ */
+void msi_lock_descs(struct device *dev)
+{
+       if (WARN_ON_ONCE(!dev->msi.data))
+               return;
+       mutex_lock(&dev->msi.data->mutex);
+}
+EXPORT_SYMBOL_GPL(msi_lock_descs);
+
+/**
+ * msi_unlock_descs - Unlock the MSI descriptor storage of a device
+ * @dev:       Device to operate on
+ */
+void msi_unlock_descs(struct device *dev)
+{
+       if (WARN_ON_ONCE(!dev->msi.data))
+               return;
+       mutex_unlock(&dev->msi.data->mutex);
+}
+EXPORT_SYMBOL_GPL(msi_unlock_descs);
+
+/**
  * msi_get_virq - Return Linux interrupt number of a MSI interrupt
  * @dev:       Device to operate on
  * @index:     MSI interrupt index to look for (0-based)