linux-kernel - Re: [PATCH v2] binder: use bitmap for faster descriptor lookup

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Date: Wed, 15 May 2024 23:42:11 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Carlos Llamas <cmllamas@...gle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Arve Hjønnevåg <arve@...roid.com>, 
	Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>, 
	Joel Fernandes <joel@...lfernandes.org>, Christian Brauner <brauner@...nel.org>, 
	Suren Baghdasaryan <surenb@...gle.com>, linux-kernel@...r.kernel.org, kernel-team@...roid.com, 
	Tim Murray <timmurray@...gle.com>, John Stultz <jstultz@...gle.com>, 
	Steven Moreland <smoreland@...gle.com>, Nick Chen <chenjia3@...o.com>
Subject: Re: [PATCH v2] binder: use bitmap for faster descriptor lookup

On Wed, May 15, 2024 at 6:43 PM Carlos Llamas <cmllamas@...gle.com> wrote:
>
> On Wed, May 15, 2024 at 04:38:51PM +0000, Carlos Llamas wrote:
> > On Wed, May 15, 2024 at 05:29:29PM +0200, Alice Ryhl wrote:
> > > On Tue, May 14, 2024 at 6:09 PM Carlos Llamas <cmllamas@...gle.com> wrote:
> > > > +static inline int
> > > > +dbitmap_get_first_zero_bit(struct dbitmap *dmap, unsigned long *bit)
> > > > +{
> > > > +       unsigned long n;
> > > > +
> > > > +       n = find_first_zero_bit(dmap->map, dmap->nbits);
> > > > +       if (unlikely(n == dmap->nbits))
> > > > +               return -ENOSPC;
> > > > +
> > > > +       *bit = n;
> > > > +       set_bit(n, dmap->map);
> > > > +
> > > > +       return 0;
> > > > +}
> > >
> > > Could we rename this method to something that makes it more clear that
> > > it's not just a getter, but that it actually also sets the bit?
> > >
> > > Alice
> >
> > Sure, what were you thinking? I had picked "get" and not just "find" to
> > indicate this behavior. However, I'll take any better ideas. The option
> > of dbitmap_find_and_set_first_zero_bit() seemed too long for me.
> >
> > --
> > Carlos Llamas
>
> I like dbitmap_acquire_first_zero_bit(). Sounds better?

acquire sounds good!

Alice