linux-kernel - Re: [PATCH] net: core: devlink.c: Use built-in RCU list checking

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Message-ID: <20200221172008.GA2181@nanopsycho>
Date:   Fri, 21 Feb 2020 18:20:08 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     madhuparnabhowmik10@...il.com
Cc:     jiri@...lanox.com, davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, joel@...lfernandes.org,
        frextrite@...il.com,
        linux-kernel-mentees@...ts.linuxfoundation.org, paulmck@...nel.org
Subject: Re: [PATCH] net: core: devlink.c: Use built-in RCU list checking

Fri, Feb 21, 2020 at 05:51:41PM CET, madhuparnabhowmik10@...il.com wrote:
>From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.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
>by default.
>
>Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

Reviewed-by: Jiri Pirko <jiri@...lanox.com>

Thanks.

However, there is a callpath where not devlink lock neither rcu read is
taken:
devlink_dpipe_table_register()->devlink_dpipe_table_find()

I guess that was not the trace you were seeing, right?


>---
> net/core/devlink.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
>diff --git a/net/core/devlink.c b/net/core/devlink.c
>index 4c63c9a4c09e..3e8c94155d93 100644
>--- a/net/core/devlink.c
>+++ b/net/core/devlink.c
>@@ -2107,7 +2107,8 @@ devlink_dpipe_table_find(struct list_head *dpipe_tables,
> {
> 	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;
> 	}
>-- 
>2.17.1
>