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Date:   Mon, 24 Feb 2020 11:52:09 +0100
From:   Jiri Pirko <jiri@resnulli.us>
To:     madhuparnabhowmik10@gmail.com
Cc:     jiri@mellanox.com, davem@davemloft.net, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, joel@joelfernandes.org,
        linux-kernel-mentees@lists.linuxfoundation.org,
        frextrite@gmail.com, paulmck@kernel.org
Subject: Re: [PATCH] net: core: devlink.c: Use built-in RCU list checking
Message-ID: <20200224105209.GB16270@nanopsycho>
References: <20200224093013.25700-1-madhuparnabhowmik10@gmail.com>
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Mon, Feb 24, 2020 at 10:30:13AM CET, madhuparnabhowmik10@gmail.com wrote:
>From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
>
>list_for_each_entry_rcu() has built-in RCU and lock checking.
>
>Pass cond argument to list_for_each_entry_rcu() to silence
>false lockdep warning when CONFIG_PROVE_RCU_LIST is enabled.
>
>The devlink->lock is held when devlink_dpipe_table_find()
>is called in non RCU read side section. Therefore, pass struct devlink
>to devlink_dpipe_table_find() for lockdep checking.
>
>Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
>---
> net/core/devlink.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
>diff --git a/net/core/devlink.c b/net/core/devlink.c
>index e82750bdc496..dadf5fa79bb1 100644
>--- a/net/core/devlink.c
>+++ b/net/core/devlink.c
>@@ -2103,11 +2103,11 @@ static int devlink_dpipe_entry_put(struct sk_buff *skb,
> 
> static struct devlink_dpipe_table *
> devlink_dpipe_table_find(struct list_head *dpipe_tables,
>-			 const char *table_name)
>+			 const char *table_name, struct devlink *devlink)
> {
> 	struct devlink_dpipe_table *table;
>-
>-	list_for_each_entry_rcu(table, dpipe_tables, list) {
>+	list_for_each_entry_rcu(table, dpipe_tables, list,
>+				lockdep_is_held(&devlink->lock)) {
> 		if (!strcmp(table->name, table_name))
> 			return table;
> 	}
>@@ -2226,7 +2226,7 @@ static int devlink_nl_cmd_dpipe_entries_get(struct sk_buff *skb,
> 
> 	table_name = nla_data(info->attrs[DEVLINK_ATTR_DPIPE_TABLE_NAME]);
> 	table = devlink_dpipe_table_find(&devlink->dpipe_table_list,
>-					 table_name);
>+					 table_name, devlink);
> 	if (!table)
> 		return -EINVAL;
> 
>@@ -2382,7 +2382,7 @@ static int devlink_dpipe_table_counters_set(struct devlink *devlink,
> 	struct devlink_dpipe_table *table;
> 
> 	table = devlink_dpipe_table_find(&devlink->dpipe_table_list,
>-					 table_name);
>+					 table_name, devlink);
> 	if (!table)
> 		return -EINVAL;
> 
>@@ -6814,7 +6814,7 @@ bool devlink_dpipe_table_counter_enabled(struct devlink *devlink,
> 
> 	rcu_read_lock();
> 	table = devlink_dpipe_table_find(&devlink->dpipe_table_list,
>-					 table_name);
>+					 table_name, devlink);
> 	enabled = false;
> 	if (table)
> 		enabled = table->counters_enabled;
>@@ -6845,7 +6845,7 @@ int devlink_dpipe_table_register(struct devlink *devlink,
> 
> 	mutex_lock(&devlink->lock);
> 
>-	if (devlink_dpipe_table_find(&devlink->dpipe_table_list, table_name)) {
>+	if (devlink_dpipe_table_find(&devlink->dpipe_table_list, table_name, devlink)) {

Run scripts/checkpatch.pl on your patch. You are breaking 80-cols limit
here.

Otherwise, the patch looks fine.

> 		err = -EEXIST;
> 		goto unlock;
> 	}
>@@ -6881,7 +6881,7 @@ void devlink_dpipe_table_unregister(struct devlink *devlink,
> 
> 	mutex_lock(&devlink->lock);
> 	table = devlink_dpipe_table_find(&devlink->dpipe_table_list,
>-					 table_name);
>+					 table_name, devlink);
> 	if (!table)
> 		goto unlock;
> 	list_del_rcu(&table->list);
>@@ -7038,7 +7038,7 @@ int devlink_dpipe_table_resource_set(struct devlink *devlink,
> 
> 	mutex_lock(&devlink->lock);
> 	table = devlink_dpipe_table_find(&devlink->dpipe_table_list,
>-					 table_name);
>+					 table_name, devlink);
> 	if (!table) {
> 		err = -EINVAL;
> 		goto out;
>-- 
>2.17.1
>