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Date:   Thu, 7 Dec 2017 11:06:34 -0500
From:   Theodore Ts'o <>
To:     Matthew Wilcox <>
Cc:     Dave Chinner <>,
        Matthew Wilcox <>,
        Ross Zwisler <>,
        Jens Axboe <>,
        Rehas Sachdeva <>,,,,,,,,
Subject: Re: [PATCH v4 72/73] xfs: Convert mru cache to XArray

On Wed, Dec 06, 2017 at 06:06:48AM -0800, Matthew Wilcox wrote:
> > Unfortunately for you, I don't find arguments along the lines of
> > "lockdep will save us" at all convincing.  lockdep already throws
> > too many false positives to be useful as a tool that reliably and
> > accurately points out rare, exciting, complex, intricate locking
> > problems.
> But it does reliably and accurately point out "dude, you forgot to take
> the lock".  It's caught a number of real problems in my own testing that
> you never got to see.

The problem is that if it has too many false positives --- and it's
gotten *way* worse with the completion callback "feature", people will
just stop using Lockdep as being too annyoing and a waste of developer
time when trying to figure what is a legitimate locking bug versus
lockdep getting confused.

<Rant>I can't even disable the new Lockdep feature which is throwing
lots of new false positives --- it's just all or nothing.</Rant>

Dave has just said he's already stopped using Lockdep, as a result.

     	      	   			      - Ted

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