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

From: Peter Zijlstra <peterz@infradead.org>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: david@redhat.com, patches@lists.linux.dev,
	linux-modules@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, pmladek@suse.com,
	petr.pavlu@suse.com, prarit@redhat.com,
	torvalds@linux-foundation.org, gregkh@linuxfoundation.org,
	rafael@kernel.org, christophe.leroy@csgroup.eu,
	tglx@linutronix.de, song@kernel.org, rppt@kernel.org,
	willy@infradead.org, vbabka@suse.cz, mhocko@suse.com,
	dave.hansen@linux.intel.com
Subject: Re: [PATCH 4/7] sempahore: add a helper for a concurrency limiter
Date: Wed, 29 Mar 2023 09:21:12 +0200	[thread overview]
Message-ID: <20230329072112.GG4253@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20230329053149.3976378-5-mcgrof@kernel.org>

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@linux-foundation.org>
> Signed-off-by: Luis Chamberlain <mcgrof@kernel.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?