linux-kernel - [PATCH v2 1/4] cdx: Introduce lock to protect controller ops and controller list

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Message-ID: <20230731120813.123247-2-abhijit.gangurde@amd.com>
Date:   Mon, 31 Jul 2023 17:38:10 +0530
From:   Abhijit Gangurde <abhijit.gangurde@....com>
To:     <gregkh@...uxfoundation.org>, <masahiroy@...nel.org>,
        <linux-kernel@...r.kernel.org>
CC:     <michal.simek@....com>, <git@....com>, <nikhil.agarwal@....com>,
        <Nipun.Gupta@....com>, Abhijit Gangurde <abhijit.gangurde@....com>
Subject: [PATCH v2 1/4] cdx: Introduce lock to protect controller ops and controller list

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 | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/cdx/cdx.c b/drivers/cdx/cdx.c
index d2cad4c670a0..66797c8fe400 100644
--- a/drivers/cdx/cdx.c
+++ b/drivers/cdx/cdx.c
@@ -72,6 +72,8 @@
 
 /* CDX controllers registered with the CDX bus */
 static DEFINE_XARRAY_ALLOC(cdx_controllers);
+/* Lock to protect controller ops and controller list */
+static DEFINE_MUTEX(cdx_controller_lock);
 
 /**
  * cdx_dev_reset - Reset a CDX device
@@ -393,6 +395,8 @@ 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);
 
@@ -405,6 +409,8 @@ static ssize_t rescan_store(const struct bus_type *bus,
 			dev_err(cdx->dev, "cdx bus scanning failed\n");
 	}
 
+	mutex_unlock(&cdx_controller_lock);
+
 	return count;
 }
 static BUS_ATTR_WO(rescan);
@@ -520,9 +526,12 @@ int cdx_register_controller(struct cdx_controller *cdx)
 {
 	int ret;
 
+	mutex_lock(&cdx_controller_lock);
+
 	ret = xa_alloc(&cdx_controllers, &cdx->id, cdx,
 		       XA_LIMIT(0, MAX_CDX_CONTROLLERS - 1), GFP_KERNEL);
 	if (ret) {
+		mutex_unlock(&cdx_controller_lock);
 		dev_err(cdx->dev,
 			"No free index available. Maximum controllers already registered\n");
 		cdx->id = (u8)MAX_CDX_CONTROLLERS;
@@ -531,6 +540,7 @@ int cdx_register_controller(struct cdx_controller *cdx)
 
 	/* Scan all the devices */
 	cdx->ops->scan(cdx);
+	mutex_unlock(&cdx_controller_lock);
 
 	return 0;
 }
@@ -541,8 +551,12 @@ void cdx_unregister_controller(struct cdx_controller *cdx)
 	if (cdx->id >= MAX_CDX_CONTROLLERS)
 		return;
 
+	mutex_lock(&cdx_controller_lock);
+
 	device_for_each_child(cdx->dev, NULL, cdx_unregister_device);
 	xa_erase(&cdx_controllers, cdx->id);
+
+	mutex_unlock(&cdx_controller_lock);
 }
 EXPORT_SYMBOL_GPL(cdx_unregister_controller);
 
-- 
2.25.1