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From:   Leon Romanovsky <leon@kernel.org>
To:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>
Cc:     Leon Romanovsky <leonro@nvidia.com>,
        Ido Schimmel <idosch@nvidia.com>,
        Ingo Molnar <mingo@redhat.com>, Jiri Pirko <jiri@nvidia.com>,
        linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
        mlxsw@nvidia.com, Moshe Shemesh <moshe@nvidia.com>,
        netdev@vger.kernel.org, Saeed Mahameed <saeedm@nvidia.com>,
        Salil Mehta <salil.mehta@huawei.com>,
        Shay Drory <shayd@nvidia.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Tariq Toukan <tariqt@nvidia.com>,
        Yisen Zhuang <yisen.zhuang@huawei.com>
Subject: [PATCH net-next v3 2/5] devlink: Annotate devlink API calls
Date:   Thu,  7 Oct 2021 09:55:16 +0300
Message-Id: <19f798d89eae110593055db5e15eb3bbf07adb2c.1633589385.git.leonro@nvidia.com>
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From: Leon Romanovsky <leonro@nvidia.com>

Initial annotation patch to separate calls that needs to be executed
before or after devlink_register().

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 net/core/devlink.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/net/core/devlink.c b/net/core/devlink.c
index 9642429cec65..4e484afeadea 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -154,6 +154,22 @@ static const struct nla_policy devlink_function_nl_policy[DEVLINK_PORT_FUNCTION_
 static DEFINE_XARRAY_FLAGS(devlinks, XA_FLAGS_ALLOC);
 #define DEVLINK_REGISTERED XA_MARK_1
 
+/* devlink instances are open to the access from the user space after
+ * devlink_register() call. Such logical barrier allows us to have certain
+ * expectations related to locking.
+ *
+ * Before *_register() - we are in initialization stage and no parallel
+ * access possible to the devlink instance. All drivers perform that phase
+ * by implicitly holding device_lock.
+ *
+ * After *_register() - users and driver can access devlink instance at
+ * the same time.
+ */
+#define ASSERT_DEVLINK_REGISTERED(d)                                           \
+	WARN_ON_ONCE(!xa_get_mark(&devlinks, (d)->index, DEVLINK_REGISTERED))
+#define ASSERT_DEVLINK_NOT_REGISTERED(d)                                       \
+	WARN_ON_ONCE(xa_get_mark(&devlinks, (d)->index, DEVLINK_REGISTERED))
+
 /* devlink_mutex
  *
  * An overall lock guarding every operation coming from userspace.
@@ -9115,6 +9131,10 @@ static void devlink_notify_unregister(struct devlink *devlink)
  */
 void devlink_register(struct devlink *devlink)
 {
+	ASSERT_DEVLINK_NOT_REGISTERED(devlink);
+	/* Make sure that we are in .probe() routine */
+	device_lock_assert(devlink->dev);
+
 	mutex_lock(&devlink_mutex);
 	xa_set_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
 	devlink_notify_register(devlink);
@@ -9129,6 +9149,10 @@ EXPORT_SYMBOL_GPL(devlink_register);
  */
 void devlink_unregister(struct devlink *devlink)
 {
+	ASSERT_DEVLINK_REGISTERED(devlink);
+	/* Make sure that we are in .remove() routine */
+	device_lock_assert(devlink->dev);
+
 	devlink_put(devlink);
 	wait_for_completion(&devlink->comp);
 
@@ -9183,6 +9207,8 @@ EXPORT_SYMBOL_GPL(devlink_reload_disable);
  */
 void devlink_free(struct devlink *devlink)
 {
+	ASSERT_DEVLINK_NOT_REGISTERED(devlink);
+
 	mutex_destroy(&devlink->reporters_lock);
 	mutex_destroy(&devlink->lock);
 	WARN_ON(!list_empty(&devlink->trap_policer_list));
-- 
2.31.1