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

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Message-Id: <20230329053149.3976378-5-mcgrof@kernel.org>
Date:   Tue, 28 Mar 2023 22:31:46 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     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
Cc:     christophe.leroy@...roup.eu, tglx@...utronix.de,
        peterz@...radead.org, song@...nel.org, rppt@...nel.org,
        willy@...radead.org, vbabka@...e.cz, mhocko@...e.com,
        dave.hansen@...ux.intel.com, mcgrof@...nel.org
Subject: [PATCH 4/7] sempahore: add a helper for a concurrency limiter

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