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

From: Luis Chamberlain <mcgrof@kernel.org>
To: 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
Cc: christophe.leroy@csgroup.eu, tglx@linutronix.de,
	peterz@infradead.org, song@kernel.org, rppt@kernel.org,
	willy@infradead.org, vbabka@suse.cz, mhocko@suse.com,
	dave.hansen@linux.intel.com, mcgrof@kernel.org
Subject: [PATCH 4/7] sempahore: add a helper for a concurrency limiter
Date: Tue, 28 Mar 2023 22:31:46 -0700	[thread overview]
Message-ID: <20230329053149.3976378-5-mcgrof@kernel.org> (raw)
In-Reply-To: <20230329053149.3976378-1-mcgrof@kernel.org>

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)
+
 static inline void sema_init(struct semaphore *sem, int val)
 {
 	static struct lock_class_key __key;
-- 
2.39.2

