linux-kernel - Re: [PATCH 4/7] sempahore: add a helper for a concurrency limiter

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Date:   Wed, 29 Mar 2023 09:21:12 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     david@...hat.com, patches@...ts.linux.dev,
        linux-modules@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, pmladek@...e.com,
        petr.pavlu@...e.com, prarit@...hat.com,
        torvalds@...ux-foundation.org, gregkh@...uxfoundation.org,
        rafael@...nel.org, christophe.leroy@...roup.eu, tglx@...utronix.de,
        song@...nel.org, rppt@...nel.org, willy@...radead.org,
        vbabka@...e.cz, mhocko@...e.com, dave.hansen@...ux.intel.com
Subject: Re: [PATCH 4/7] sempahore: add a helper for a concurrency limiter

On Tue, Mar 28, 2023 at 10:31:46PM -0700, Luis Chamberlain wrote:
> While I looked at re-using the old kernel/kmod.c (now kernel/module/kmod.c)
> concurrency delimiter methodology for another place in the kernel Linus
> noted that this could be simply replaced with a sempahore [0].
> 
> So add that so we we don't re-invent the wheel and make it obvious to use.
> 
> [0] https://lore.kernel.org/all/CAHk-=whkj6=wyi201JXkw9iT_eTUTsSx+Yb9d4OgmZFjDJA18g@mail.gmail.com/
> 
> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
> ---
>  include/linux/semaphore.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/include/linux/semaphore.h b/include/linux/semaphore.h
> index 6694d0019a68..2ecdffdb9814 100644
> --- a/include/linux/semaphore.h
> +++ b/include/linux/semaphore.h
> @@ -28,6 +28,9 @@ struct semaphore {
>  #define DEFINE_SEMAPHORE(name)	\
>  	struct semaphore name = __SEMAPHORE_INITIALIZER(name, 1)
>  
> +#define CONCURRENCY_LIMITER(name, n) \
> +	struct semaphore name = __SEMAPHORE_INITIALIZER(name, n)
> +

Why should this live in semaphore.h?