From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
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,
frextrite@gmail.com,
linux-kernel-mentees@lists.linuxfoundation.org,
paulmck@kernel.org
Subject: Re: [PATCH] net: core: devlink.c: Use built-in RCU list checking
Date: Fri, 21 Feb 2020 23:05:34 +0530 [thread overview]
Message-ID: <20200221173533.GA13198@madhuparna-HP-Notebook> (raw)
In-Reply-To: <20200221172008.GA2181@nanopsycho>
On Fri, Feb 21, 2020 at 06:20:08PM +0100, Jiri Pirko wrote:
> Fri, Feb 21, 2020 at 05:51:41PM 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
> >by default.
> >
> >Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
>
> Reviewed-by: Jiri Pirko <jiri@mellanox.com>
>
> Thanks.
>
> However, there is a callpath where not devlink lock neither rcu read is
> taken:
> devlink_dpipe_table_register()->devlink_dpipe_table_find()
>
Hi,
Yes I had noticed this, but I was not sure if there is some other lock
which is being used.
If yes, then can you please tell me which lock is held in this case,
and I can add that condition as well to list_for_each_entry_rcu() usage.
And if no lock or rcu_read_lock is held then may be we should
use rcu_read_lock/unlock here.
Let me know what you think about this.
Thank you,
Madhuparna
> 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
> >
next prev parent reply other threads:[~2020-02-21 17:36 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-21 16:51 [PATCH] net: core: devlink.c: Use built-in RCU list checking madhuparnabhowmik10
2020-02-21 17:20 ` Jiri Pirko
2020-02-21 17:35 ` Madhuparna Bhowmik [this message]
2020-02-21 17:54 ` Jiri Pirko
2020-02-21 18:00 ` Madhuparna Bhowmik
2020-02-23 11:03 ` Madhuparna Bhowmik
2020-02-23 18:19 ` Jiri Pirko
2020-02-24 0:28 ` kbuild test robot
2020-02-24 9:30 madhuparnabhowmik10
2020-02-24 10:52 ` Jiri Pirko
2020-02-25 12:09 ` Madhuparna Bhowmik
2020-02-25 12:27 madhuparnabhowmik10
2020-02-25 13:06 ` Jiri Pirko
2020-02-27 0:59 ` David Miller
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