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

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Date:   Sat, 26 Jan 2019 14:16:24 +0800
From:   Zheng Xiang <zhengxiang9@...wei.com>
To:     <linux-kernel@...r.kernel.org>
CC:     <tglx@...utronix.de>, <jason@...edaemon.net>,
        <marc.zyngier@....com>, <wanghaibin.wang@...wei.com>,
        Zheng Xiang <zhengxiang9@...wei.com>
Subject: [PATCH] irqchip/gic-v3-its: Lock its device list during find and create its device

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 <zhengxiang9@...wei.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