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

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Message-id: <172651905368.17050.16487291202431244979@noble.neil.brown.name>
Date: Tue, 17 Sep 2024 06:37:33 +1000
From: "NeilBrown" <neilb@...e.de>
To: "Peter Zijlstra" <peterz@...radead.org>
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 Tue, 17 Sep 2024, Peter Zijlstra wrote:
> On Mon, Sep 16, 2024 at 09:48:11PM +1000, NeilBrown wrote:
> > On Mon, 16 Sep 2024, Peter Zijlstra wrote:
> > > 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 *' ?
> > 
> > Sorry, that is meant so as "the corresponding wait_on_bit()".
> > 
> > 
> > > 
> > > > 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.
> > > 
> > 
> > Again - wake_up_bit().  Sorry - bits are vars were swimming around my
> > brain and I didn't proof-read properly.
> > 
> > This patch is all "bit", no "var".
> 
> OK :-)
> 
> Anyway, other than that the patches look fine, but given we're somewhat
> in the middle of the merge window and all traveling to get into Vienna
> and have a few beers, I would much prefer merging these patches after
> -rc1, that okay?
> 

Yes, that's OK.  Thanks for having a look.  Have fun in Vienna.

NeilBrown