linux-kernel - Re: linux-next: manual merge of the workqueues tree with the tip tree

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Message-ID: <20191118090000.hpnibmk6xculuwii@linutronix.de>
Date:   Mon, 18 Nov 2019 10:00:00 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Tejun Heo <tj@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: linux-next: manual merge of the workqueues tree with the tip tree

On 2019-11-18 15:08:58 [+1100], Stephen Rothwell wrote:
> Hi all,
Hi,

> Today's linux-next merge of the workqueues tree got a conflict in:
> 
>   kernel/workqueue.c
> 
> between commit:
> 
>   5a6446626d7e ("workqueue: Convert for_each_wq to use built-in list check")
> 
> from the tip tree and commit:
> 
>   49e9d1a9faf2 ("workqueue: Add RCU annotation for pwq list walk")
> 
> from the workqueues tree.

urgh. So the RCU warning is introduced in commit
   28875945ba98d ("rcu: Add support for consolidated-RCU reader checking")

which was merged in v5.4-rc1. I enabled it around -rc7 and saw a few
warnings including in the workqueue code. I asked about this and posted
later a patch which was applied by Tejun. Now I see that the tip tree
has a patch for this warning…
I would vote for the patch in -tip since it also removes the
assert_rcu_or_wq_mutex() macro.
It would be nice if this could be part of v5.4 since once the RCU
warning is enabled it will yell.

Sebastian