linux-kernel - [PATCH v3 2/5] cdx: Introduce lock to protect controller ops

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Date:   Mon, 14 Aug 2023 15:52:20 +0530
From:   Abhijit Gangurde <abhijit.gangurde@....com>
To:     <gregkh@...uxfoundation.org>, <masahiroy@...nel.org>,
        <linux-kernel@...r.kernel.org>
CC:     <Nipun.Gupta@....com>, <nikhil.agarwal@....com>,
        <puneet.gupta@....com>, <git@....com>, <michal.simek@....com>,
        Abhijit Gangurde <abhijit.gangurde@....com>
Subject: [PATCH v3 2/5] cdx: Introduce lock to protect controller ops

Add a mutex lock to prevent race between controller ops initiated by
the bus subsystem and the controller registration/unregistration.

Signed-off-by: Abhijit Gangurde <abhijit.gangurde@....com>
---
 drivers/cdx/cdx.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/cdx/cdx.c b/drivers/cdx/cdx.c
index 1c0f76cf4f15..50df061f4537 100644
--- a/drivers/cdx/cdx.c
+++ b/drivers/cdx/cdx.c
@@ -72,6 +72,8 @@
 
 /* IDA for CDX controllers registered with the CDX bus */
 DEFINE_IDA(cdx_controller_ida);
+/* Lock to protect controller ops */
+static DEFINE_MUTEX(cdx_controller_lock);
 
 static char *compat_node_name = "xlnx,versal-net-cdx";
 
@@ -396,6 +398,8 @@ static ssize_t rescan_store(const struct bus_type *bus,
 	if (!val)
 		return -EINVAL;
 
+	mutex_lock(&cdx_controller_lock);
+
 	/* Unregister all the devices on the bus */
 	cdx_unregister_devices(&cdx_bus_type);
 
@@ -415,6 +419,8 @@ static ssize_t rescan_store(const struct bus_type *bus,
 		put_device(&pd->dev);
 	}
 
+	mutex_unlock(&cdx_controller_lock);
+
 	return count;
 }
 static BUS_ATTR_WO(rescan);
@@ -538,11 +544,13 @@ int cdx_register_controller(struct cdx_controller *cdx)
 		return ret;
 	}
 
+	mutex_lock(&cdx_controller_lock);
 	cdx->id = ret;
 
 	/* Scan all the devices */
 	cdx->ops->scan(cdx);
 	cdx->controller_registered = true;
+	mutex_unlock(&cdx_controller_lock);
 
 	return 0;
 }
@@ -553,9 +561,13 @@ void cdx_unregister_controller(struct cdx_controller *cdx)
 	if (cdx->id >= MAX_CDX_CONTROLLERS)
 		return;
 
+	mutex_lock(&cdx_controller_lock);
+
 	cdx->controller_registered = false;
 	device_for_each_child(cdx->dev, NULL, cdx_unregister_device);
 	ida_free(&cdx_controller_ida, cdx->id);
+
+	mutex_unlock(&cdx_controller_lock);
 }
 EXPORT_SYMBOL_GPL(cdx_unregister_controller);
 
-- 
2.25.1