linux-kernel - Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock

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Date:	Mon, 4 Apr 2016 18:02:41 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Sedat Dilek <sedat.dilek@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Alfredo Alvarez Fernandez <alfredoalvarezfernandez@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Theodore Ts'o <tytso@....edu>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at
 kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260

On Mon, Apr 04, 2016 at 05:31:40PM +0200, Sedat Dilek wrote:
> > +/* https://en.wikipedia.org/wiki/Xorshift#xorshift.2A */
> > +#define UINT64_C(x) x##ULL
> > +static inline u64 xorshift64star(u64 x)
> > +{
> > +       x ^= x >> 12; // a
> > +       x ^= x << 25; // b
> > +       x ^= x >> 27; // c
> > +       return x * UINT64_C(2685821657736338717);
> > +}

> Will you push that also to peterz/queue.git#locking/urgent?

Only after I've had a play and observed it making any difference; Dmitry
supposedly has a reproducer, but I've not yet had a moment to try.

> - Sedat -
> 
> P.S.: "lockdep: print chain_key collision information" in your above
> tree differs from the upstream one.

I'll drop mine, I just hadn't moved to the very latestestest tip.