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From:   Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Date:   Tue, 25 Feb 2020 17:39:08 +0530
To:     Jiri Pirko <jiri@resnulli.us>
Cc:     madhuparnabhowmik10@gmail.com, 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: <20200225120908.GA29836@madhuparna-HP-Notebook>
References: <20200224093013.25700-1-madhuparnabhowmik10@gmail.com>
 <20200224105209.GB16270@nanopsycho>
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On Mon, Feb 24, 2020 at 11:52:09AM +0100, Jiri Pirko wrote:
> 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.
>
Sure, I will take care of this and send the updated patch soon.

Thank you,
Madhuparna
> 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
> >