[PATCH] irqchip/gic-v3-its: Lock its device list during find and create its device

[Zheng Xiang]

Currently each PCI device under a PCI Bridge shares the same device id
and ITS device. Assume there are two PCI devices call its_msi_prepare
concurrently and they are both going to find and create their ITS
device. There is a chance that the later one couldn't find ITS device
before the other one creating the ITS device. It will cause the later
one to create a different ITS device even if they have the same
device_id.

Signed-off-by: Zheng Xiang <zhengxia...@huawei.com>
---
 drivers/irqchip/irq-gic-v3-its.c | 52 +++++++++++++++-------------------------
 1 file changed, 19 insertions(+), 33 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index db20e99..397edc8 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -2205,25 +2205,6 @@ static void its_cpu_init_collections(void)
        raw_spin_unlock(&its_lock);
 }
 
-static struct its_device *its_find_device(struct its_node *its, u32 dev_id)
-{
-       struct its_device *its_dev = NULL, *tmp;
-       unsigned long flags;
-
-       raw_spin_lock_irqsave(&its->lock, flags);
-
-       list_for_each_entry(tmp, &its->its_device_list, entry) {
-               if (tmp->device_id == dev_id) {
-                       its_dev = tmp;
-                       break;
-               }
-       }
-
-       raw_spin_unlock_irqrestore(&its->lock, flags);
-
-       return its_dev;
-}
-
 static struct its_baser *its_get_baser(struct its_node *its, u32 type)
 {
        int i;
@@ -2321,7 +2302,7 @@ static bool its_alloc_vpe_table(u32 vpe_id)
 static struct its_device *its_create_device(struct its_node *its, u32 dev_id,
                                            int nvecs, bool alloc_lpis)
 {
-       struct its_device *dev;
+       struct its_device *dev = NULL, *tmp;
        unsigned long *lpi_map = NULL;
        unsigned long flags;
        u16 *col_map = NULL;
@@ -2331,6 +2312,24 @@ static struct its_device *its_create_device(struct 
its_node *its, u32 dev_id,
        int nr_ites;
        int sz;
 
+       raw_spin_lock_irqsave(&its->lock, flags);
+       list_for_each_entry(tmp, &its->its_device_list, entry) {
+               if (tmp->device_id == dev_id) {
+                       dev = tmp;
+                       break;
+               }
+       }
+       if (dev) {
+               /*
+                * We already have seen this ID, probably through
+                * another alias (PCI bridge of some sort). No need to
+                * create the device.
+                */
+               pr_debug("Reusing ITT for devID %x\n", dev_id);
+               raw_spin_unlock_irqrestore(&its->lock, flags);
+               return dev;
+       }
+
        if (!its_alloc_device_table(its, dev_id))
                return NULL;
 
@@ -2378,7 +2377,6 @@ static struct its_device *its_create_device(struct 
its_node *its, u32 dev_id,
        dev->device_id = dev_id;
        INIT_LIST_HEAD(&dev->entry);
 
-       raw_spin_lock_irqsave(&its->lock, flags);
        list_add(&dev->entry, &its->its_device_list);
        raw_spin_unlock_irqrestore(&its->lock, flags);
 
@@ -2443,23 +2441,11 @@ static int its_msi_prepare(struct irq_domain *domain, 
struct device *dev,
                return -EINVAL;
        }
 
-       its_dev = its_find_device(its, dev_id);
-       if (its_dev) {
-               /*
-                * We already have seen this ID, probably through
-                * another alias (PCI bridge of some sort). No need to
-                * create the device.
-                */
-               pr_debug("Reusing ITT for devID %x\n", dev_id);
-               goto out;
-       }
-
        its_dev = its_create_device(its, dev_id, nvec, true);
        if (!its_dev)
                return -ENOMEM;
 
        pr_debug("ITT %d entries, %d bits\n", nvec, ilog2(nvec));
-out:
        info->scratchpad[0].ptr = its_dev;
        return 0;
 }
-- 
1.8.3.1