linux-kernel - Re: waitqueue lockdep annotation

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Message-ID: <20171206235141.GB17876@lst.de>
Date:   Thu, 7 Dec 2017 00:51:41 +0100
From:   Christoph Hellwig <hch@....de>
To:     Jason Baron <jbaron@...mai.com>
Cc:     Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dave@...olabs.net>
Subject: Re: waitqueue lockdep annotation

On Tue, Dec 05, 2017 at 10:24:34AM -0500, Jason Baron wrote:
> On 12/01/2017 06:03 PM, Christoph Hellwig wrote:
> > On Fri, Dec 01, 2017 at 05:34:50PM -0500, Jason Baron wrote:
> >> hmmm...I'm not sure how this suggestion would change the locking rules
> >> from what we currently have. Right now, we use ep->lock, if we remove
> >> that and use ep->wq->lock instead, there is just a 1-to-1 mapping there
> >> that has not changed, since ep->wq->lock currently is completely not
> >> being used.
> > 
> > True.  The patch below survives the amazing complex booting and starting
> > systemd with lockdep enabled test.  Do we have something resembling a
> > epoll test suite?
> >
> 
> I don't think we have any in the kernel tree proper (other than some
> selftests using epoll) but there are tests in ltp and some performance
> tests such as:
> 
> http://linux-scalability.org/epoll/epoll-test.c

That one just seems to keep running until interrupted.  I've run
it for a while and it seems fine, but I doesn't seem to get any
ok/failed kind of status.

> http://www.xmailserver.org/linux-patches/pipetest.c

Seems to work fine as well, so I'm going to resend the updated patch.