Netdev Archive on lore.kernel.org
help / color / mirror / Atom feed
From: David Miller <davem@davemloft.net>
To: kuba@kernel.org
Cc: netdev@vger.kernel.org, paulmck@kernel.org,
	joel@joelfernandes.org, josh@joshtriplett.org,
	peterz@infradead.org, christian.brauner@ubuntu.com,
	rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
	nikolay@cumulusnetworks.com, sfr@canb.auug.org.au,
	roopa@nvidia.com
Subject: Re: [PATCH net-next] rcu: prevent RCU_LOCKDEP_WARN() from swallowing the condition
Date: Tue, 08 Sep 2020 20:12:40 -0700 (PDT)	[thread overview]
Message-ID: <20200908.201240.821919587285621499.davem@davemloft.net> (raw)
In-Reply-To: <20200908173624.160024-1-kuba@kernel.org>

From: Jakub Kicinski <kuba@kernel.org>
Date: Tue,  8 Sep 2020 10:36:24 -0700

> We run into a unused variable warning in bridge code when
> variable is only used inside the condition of
> rcu_dereference_protected().
> 
>  #define mlock_dereference(X, br) \
> 	rcu_dereference_protected(X, lockdep_is_held(&br->multicast_lock))
> 
> Since on builds with CONFIG_PROVE_RCU=n rcu_dereference_protected()
> compiles to nothing the compiler doesn't see the variable use.
> 
> Prevent the warning by adding the condition as dead code.
> We need to un-hide the declaration of lockdep_tasklist_lock_is_held()
> and fix a bug the crept into a net/sched header.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

I ended up applying Nikolay's fix, but this situation with the rcu macros
needs to be addressed.

      parent reply	other threads:[~2020-09-09  3:12 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-08  3:00 linux-next: build warning after merge of the net-next tree Stephen Rothwell
2020-09-08  3:49 ` Jakub Kicinski
2020-09-08  7:17 ` [PATCH net-next] net: bridge: mcast: fix unused br var when lockdep isn't defined Nikolay Aleksandrov
2020-09-08 16:00   ` Jakub Kicinski
2020-09-08 16:09     ` nikolay
2020-09-08 17:36     ` [PATCH net-next] rcu: prevent RCU_LOCKDEP_WARN() from swallowing the condition Jakub Kicinski
2020-09-08 18:15       ` nikolay
2020-09-09  0:27         ` Jakub Kicinski
2020-09-14 20:21           ` Joel Fernandes
2020-09-14 22:47             ` Jakub Kicinski
2020-09-15  0:20               ` Paul E. McKenney
2020-09-15  0:30                 ` Jakub Kicinski
2020-09-15 17:02                   ` Paul E. McKenney
2020-09-15  1:34               ` Joel Fernandes
2020-09-09  3:12       ` David Miller [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200908.201240.821919587285621499.davem@davemloft.net \
    --to=davem@davemloft.net \
    --cc=christian.brauner@ubuntu.com \
    --cc=joel@joelfernandes.org \
    --cc=josh@joshtriplett.org \
    --cc=kuba@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=nikolay@cumulusnetworks.com \
    --cc=paulmck@kernel.org \
    --cc=peterz@infradead.org \
    --cc=rcu@vger.kernel.org \
    --cc=roopa@nvidia.com \
    --cc=sfr@canb.auug.org.au \
    --subject='Re: [PATCH net-next] rcu: prevent RCU_LOCKDEP_WARN() from swallowing the condition' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).