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Date: Thu, 9 Apr 2015 10:12:07 -0700
Message-ID: <CA+55aFwNgcWpcWZ31VAZOJtKSwdhaqHQOJ6hDifhr7eyAEPxag@mail.gmail.com>
Subject: Re: [PATCH v4 6/9] rbtree: Implement generic latch_tree
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>, Ingo Molnar <mingo@kernel.org>,
        Rusty Russell <rusty@rustcorp.com.au>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andi Kleen <andi@firstfloor.org>, Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Michel Lespinasse <walken@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        David Woodhouse <David.Woodhouse@intel.com>,
        Rik van Riel <riel@redhat.com>
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On Thu, Apr 9, 2015 at 9:59 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> I was a little surprised myself it worked, but its a constant after
> all so it 'should'.

Well, it should actually work for non-constants too, even when that
'idx' isn't inlined to one of the fixed constants. So even if this
will ever hit the "seq & 1" case for lookup, it should all work. It's
just an expression, after all.

All that is really required is that you can do '&(x->y)' on it, where
'x' is the type, and 'y' is the "member".

It's just unusual, which I think makes it slightly harder to read for
a *human* just because it breaks the normal pattern of those things.
But there's nothing technically wrong with it.

                        Linus
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