[PATCH] ACPI / HOTPLUG: fix device->physical_node_lock deadlock

[Xie XiuQi]

I meet a deadlock during cpu hotplug. The code path is bellow:

Call Trace:
 [<ffffffff816e373c>] dump_stack+0x19/0x1b
 [<ffffffff810fd85a>] validate_chain.isra.43+0xf4a/0x1120
 [<ffffffff810236c9>] ? sched_clock+0x9/0x10
 [<ffffffff810ca8bd>] ? sched_clock_local+0x1d/0x80
 [<ffffffff810caa88>] ? sched_clock_cpu+0xa8/0x100
 [<ffffffff810fe846>] __lock_acquire+0x3c6/0xb70
 [<ffffffff810caa88>] ? sched_clock_cpu+0xa8/0x100
 [<ffffffff810ff7e2>] lock_acquire+0xa2/0x1f0
 [<ffffffff813ba132>] ? acpi_scan_is_offline+0x2c/0xa3
 [<ffffffff816e7a14>] mutex_lock_nested+0x94/0x3f0
 [<ffffffff813ba132>] ? acpi_scan_is_offline+0x2c/0xa3
 [<ffffffff813ba132>] ? acpi_scan_is_offline+0x2c/0xa3
 [<ffffffff810fe0fd>] ? trace_hardirqs_on+0xd/0x10
 [<ffffffff813ba132>] acpi_scan_is_offline+0x2c/0xa3	--> LOCK (DEADLOCK)
 [<ffffffff813fdac8>] acpi_container_offline+0x32/0x4e
 [<ffffffff81469e59>] container_offline+0x19/0x20
 [<ffffffff81462955>] device_offline+0x95/0xc0
 [<ffffffff813b9e53>] acpi_bus_offline+0xbc/0x126	--> LOCK
 [<ffffffff813bb83d>] acpi_device_hotplug+0x236/0x46b
 [<ffffffff813b4c75>] acpi_hotplug_work_fn+0x1e/0x29
 [<ffffffff810a6c10>] process_one_work+0x220/0x710
 [<ffffffff810a6ba4>] ? process_one_work+0x1b4/0x710
 [<ffffffff810a721b>] worker_thread+0x11b/0x3a0
 [<ffffffff810a7100>] ? process_one_work+0x710/0x710
 [<ffffffff810b061d>] kthread+0xed/0x100
 [<ffffffff810b0530>] ? insert_kthread_work+0x80/0x80
 [<ffffffff816f663c>] ret_from_fork+0x7c/0xb0
 [<ffffffff810b0530>] ? insert_kthread_work+0x80/0x80

This deadlock was introduced by commit caa73ea
("ACPI / hotplug / driver core: Handle containers in a special way").

In this patch, we just introduced a lockless version __acpi_scan_is_offline()
for acpi_container_offline(), to avoid this deadlock.

Cc: <stable@xxxxxxxxxxxxxxx> # v3.14+
Signed-off-by: Xie XiuQi <xiexiuqi@xxxxxxxxxx>
---
 drivers/acpi/container.c |  2 +-
 drivers/acpi/internal.h  |  1 +
 drivers/acpi/scan.c      | 15 ++++++++++++---
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/container.c b/drivers/acpi/container.c
index c8ead9f..43bda3b2 100644
--- a/drivers/acpi/container.c
+++ b/drivers/acpi/container.c
@@ -50,7 +50,7 @@ static int acpi_container_offline(struct container_dev *cdev)
 
 	/* Check all of the dependent devices' physical companions. */
 	list_for_each_entry(child, &adev->children, node)
-		if (!acpi_scan_is_offline(child, false))
+		if (!__acpi_scan_is_offline(child, false))
 			return -EBUSY;
 
 	return 0;
diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 56b321a..3b7a07b 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -80,6 +80,7 @@ void acpi_apd_init(void);
 acpi_status acpi_hotplug_schedule(struct acpi_device *adev, u32 src);
 bool acpi_queue_hotplug_work(struct work_struct *work);
 void acpi_device_hotplug(struct acpi_device *adev, u32 src);
+bool __acpi_scan_is_offline(struct acpi_device *adev, bool uevent);
 bool acpi_scan_is_offline(struct acpi_device *adev, bool uevent);
 
 /* --------------------------------------------------------------------------
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index bbca783..ea55a9a 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -293,13 +293,12 @@ acpi_device_modalias_show(struct device *dev, struct device_attribute *attr, cha
 }
 static DEVICE_ATTR(modalias, 0444, acpi_device_modalias_show, NULL);
 
-bool acpi_scan_is_offline(struct acpi_device *adev, bool uevent)
+/* Must be called under physical_node_lock. */
+bool __acpi_scan_is_offline(struct acpi_device *adev, bool uevent)
 {
 	struct acpi_device_physical_node *pn;
 	bool offline = true;
 
-	mutex_lock(&adev->physical_node_lock);
-
 	list_for_each_entry(pn, &adev->physical_node_list, node)
 		if (device_supports_offline(pn->dev) && !pn->dev->offline) {
 			if (uevent)
@@ -309,7 +308,17 @@ bool acpi_scan_is_offline(struct acpi_device *adev, bool uevent)
 			break;
 		}
 
+	return offline;
+}
+
+bool acpi_scan_is_offline(struct acpi_device *adev, bool uevent)
+{
+	bool offline = true;
+
+	mutex_lock(&adev->physical_node_lock);
+	offline = __acpi_scan_is_offline(adev, uevent);
 	mutex_unlock(&adev->physical_node_lock);
+
 	return offline;
 }
 
-- 
1.8.3.1

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