linux-kernel - Re: [RFC][PATCH] sched/wait_bit: Introduce wait_var_event()/wake_up

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Message-ID: <18971.1521125120@warthog.procyon.org.uk>
Date:   Thu, 15 Mar 2018 14:45:20 +0000
From:   David Howells <dhowells@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     dhowells@...hat.com, Dan Williams <dan.j.williams@...el.com>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Ingo Molnar <mingo@...hat.com>, Christoph Hellwig <hch@....de>,
        david <david@...morbit.com>,
        linux-xfs <linux-xfs@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Jan Kara <jack@...e.cz>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ralf Baechle <ralf@...ux-mips.org>
Subject: Re: [RFC][PATCH] sched/wait_bit: Introduce wait_var_event()/wake_up_var()

Peter Zijlstra <peterz@...radead.org> wrote:

> Does the below address things sufficiently clear?

Yep.

> +wait_queue_head_t *__var_waitqueue(void *p)
> +{
> +	if (BITS_PER_LONG == 64) {
> +		unsigned long q = (unsigned long)p;
> +
> +		return bit_waitqueue((void *)(q & ~1), q & 1);
> +	}
> +	return bit_waitqueue(p, 0);
> +}

You might be better off not using bit_waitqueue() but rather do the
calculation directly since you don't actually have a bit number.

David