From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
In general, acpi_bus_attach() can only be run safely under
acpi_scan_lock, but that lock cannot be acquired under
acpi_dep_list_lock, so make acpi_scan_clear_dep() schedule deferred
execution of acpi_bus_attach() under acpi_scan_lock instead of
calling it directly.
This also fixes a possible race between acpi_scan_clear_dep() and
device removal that might cause a device object that went away to
be accessed, because acpi_scan_clear_dep() is changed to acquire
a reference on the consumer device object.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
drivers/acpi/scan.c | 50 +++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 45 insertions(+), 5 deletions(-)
Index: linux-pm/drivers/acpi/scan.c
===================================================================
--- linux-pm.orig/drivers/acpi/scan.c
+++ linux-pm/drivers/acpi/scan.c
@@ -2115,16 +2115,56 @@ static int acpi_dev_get_first_consumer_d
return 0;
}
-static int acpi_scan_clear_dep(struct acpi_dep_data *dep, void *data)
-{
+struct acpi_scan_clear_dep_work {
+ struct work_struct work;
struct acpi_device *adev;
+};
+
+static void acpi_scan_clear_dep_fn(struct work_struct *work)
+{
+ struct acpi_scan_clear_dep_work *cdw;
+
+ cdw = container_of(work, struct acpi_scan_clear_dep_work, work);
- acpi_bus_get_device(dep->consumer, &adev);
+ acpi_scan_lock_acquire();
+ acpi_bus_attach(cdw->adev, true);
+ acpi_scan_lock_release();
+
+ acpi_dev_put(cdw->adev);
+ kfree(cdw);
+}
+
+static bool acpi_scan_clear_dep_queue(struct acpi_device *adev)
+{
+ struct acpi_scan_clear_dep_work *cdw;
+
+ if (adev->dep_unmet)
+ return false;
+
+ cdw = kmalloc(sizeof(*cdw), GFP_KERNEL);
+ if (!cdw)
+ return false;
+
+ cdw->adev = adev;
+ INIT_WORK(&cdw->work, acpi_scan_clear_dep_fn);
+ /*
+ * Since the work function may block on the lock until the entire
+ * initial enumeration of devices is complete, put it into the unbound
+ * workqueue.
+ */
+ queue_work(system_unbound_wq, &cdw->work);
+
+ return true;
+}
+
+static int acpi_scan_clear_dep(struct acpi_dep_data *dep, void *data)
+{
+ struct acpi_device *adev = acpi_bus_get_acpi_device(dep->consumer);
if (adev) {
adev->dep_unmet--;
- if (!adev->dep_unmet)
- acpi_bus_attach(adev, true);
+ if (!acpi_scan_clear_dep_queue(adev))
+ acpi_dev_put(adev);
}
list_del(&dep->node);
