linux-kernel - Re: [PATCH 2/7] sched: change wake_up_bit() and related function to expect unsigned long *

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Message-ID: <20240916112810.GY4723@noisy.programming.kicks-ass.net>
Date: Mon, 16 Sep 2024 13:28:10 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: NeilBrown <neilb@...e.de>
Cc: Ingo Molnar <mingo@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH 2/7] sched: change wake_up_bit() and related function to
 expect unsigned long *

On Mon, Aug 26, 2024 at 04:30:59PM +1000, NeilBrown wrote:
> wake_up_bit() currently allows a "void *".  While this isn't strictly a
> problem as the address is never dereferenced, it is inconsistent with
> the corresponding wait_var_event() which requires "unsigned long *" and
> does dereference the pointer.

I'm having trouble parsing this. The way I read it, you're contradicting
yourself. Where does wait_var_event() require 'unsigned long *' ?

> And code that needs to wait for a change in something other than an
> unsigned long would be better served by wake_up_var().

This, afaict the whole var thing is size invariant. It only cares about
the address.