Patch "cxl/acpi: Move rescan to the workqueue" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    cxl/acpi: Move rescan to the workqueue

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     cxl-acpi-move-rescan-to-the-workqueue.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 2c6aa71b070247d3da2b5ed5820e41eb07a2cf17
Author: Dan Williams <dan.j.williams@xxxxxxxxx>
Date:   Thu Dec 1 13:33:48 2022 -0800

    cxl/acpi: Move rescan to the workqueue
    
    [ Upstream commit 4029c32fb601d505dfb92bdf0db9fdcc41fe1434 ]
    
    Now that the cxl_mem driver has a need to take the root device lock, the
    cxl_bus_rescan() needs to run outside of the root lock context. That
    need arises from RCH topologies and the locking that the cxl_mem driver
    does to attach a descendant to an upstream port. In the RCH case the
    lock needed is the CXL root device lock [1].
    
    Link: http://lore.kernel.org/r/166993045621.1882361.1730100141527044744.stgit@xxxxxxxxxxxxxxxxxxxxxxxxx [1]
    Tested-by: Robert Richter <rrichter@xxxxxxx>
    Link: http://lore.kernel.org/r/166993042884.1882361.5633723613683058881.stgit@xxxxxxxxxxxxxxxxxxxxxxxxx
    Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
    Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
    Stable-dep-of: 3d6ebf16438d ("cxl/port: Fix cxl_bus_rescan() vs bus_rescan_devices()")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index dd610556a3afa..d7d789211c173 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -509,7 +509,8 @@ static int cxl_acpi_probe(struct platform_device *pdev)
 		return rc;
 
 	/* In case PCI is scanned before ACPI re-trigger memdev attach */
-	return cxl_bus_rescan();
+	cxl_bus_rescan();
+	return 0;
 }
 
 static const struct acpi_device_id cxl_acpi_ids[] = {
@@ -533,7 +534,19 @@ static struct platform_driver cxl_acpi_driver = {
 	.id_table = cxl_test_ids,
 };
 
-module_platform_driver(cxl_acpi_driver);
+static int __init cxl_acpi_init(void)
+{
+	return platform_driver_register(&cxl_acpi_driver);
+}
+
+static void __exit cxl_acpi_exit(void)
+{
+	platform_driver_unregister(&cxl_acpi_driver);
+	cxl_bus_drain();
+}
+
+module_init(cxl_acpi_init);
+module_exit(cxl_acpi_exit);
 MODULE_LICENSE("GPL v2");
 MODULE_IMPORT_NS(CXL);
 MODULE_IMPORT_NS(ACPI);
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 1f1483a9e5252..f0875fa86c616 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -1786,12 +1786,27 @@ static void cxl_bus_remove(struct device *dev)
 
 static struct workqueue_struct *cxl_bus_wq;
 
-int cxl_bus_rescan(void)
+static void cxl_bus_rescan_queue(struct work_struct *w)
 {
-	return bus_rescan_devices(&cxl_bus_type);
+	int rc = bus_rescan_devices(&cxl_bus_type);
+
+	pr_debug("CXL bus rescan result: %d\n", rc);
+}
+
+void cxl_bus_rescan(void)
+{
+	static DECLARE_WORK(rescan_work, cxl_bus_rescan_queue);
+
+	queue_work(cxl_bus_wq, &rescan_work);
 }
 EXPORT_SYMBOL_NS_GPL(cxl_bus_rescan, CXL);
 
+void cxl_bus_drain(void)
+{
+	drain_workqueue(cxl_bus_wq);
+}
+EXPORT_SYMBOL_NS_GPL(cxl_bus_drain, CXL);
+
 bool schedule_cxl_memdev_detach(struct cxl_memdev *cxlmd)
 {
 	return queue_work(cxl_bus_wq, &cxlmd->detach_work);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 7750ccb7652db..827fa94cddda1 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -564,7 +564,8 @@ struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,
 				   struct cxl_dport *parent_dport);
 struct cxl_port *find_cxl_root(struct device *dev);
 int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd);
-int cxl_bus_rescan(void);
+void cxl_bus_rescan(void);
+void cxl_bus_drain(void);
 struct cxl_port *cxl_mem_find_port(struct cxl_memdev *cxlmd,
 				   struct cxl_dport **dport);
 bool schedule_cxl_memdev_detach(struct cxl_memdev *cxlmd);