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Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1phQ7O-006msJ-22; Wed, 29 Mar 2023 07:21:15 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 89D5C3002A3; Wed, 29 Mar 2023 09:21:12 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 2C6962CBE6E9B; Wed, 29 Mar 2023 09:21:12 +0200 (CEST) Date: Wed, 29 Mar 2023 09:21:12 +0200 From: Peter Zijlstra To: Luis Chamberlain 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 Message-ID: <20230329072112.GG4253@hirez.programming.kicks-ass.net> References: <20230329053149.3976378-1-mcgrof@kernel.org> <20230329053149.3976378-5-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230329053149.3976378-5-mcgrof@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: 4u4htjitts4ab9yaktzacikdkw3quu8w X-Rspamd-Queue-Id: BAAEC4000C X-HE-Tag: 1680074482-516279 X-HE-Meta: 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 9TWSJYV+ 5Ugqq+4FwKrViPRyekim/CruS+UTMeHyc9COSVMhIyczZuSUaLQ7ameckIlcL6Jt7jaKh+c8rVH80bUCZR79Eab3/9Vq9x6MsPo0uEbD5Ogzy6ILc0gCRlJgyvlCj5WGxaoK2yW4KpHgom6rxdEveDS1VXSDIgpnFC/xcAxIpfqRUHyZf+yKAa1yaUUjqk60NnaNvQyTvF4uND8LzIB0DJfuiBAl2cEn0g4/Fw+RZepyH3nbJ7y0CycXv1a91vvF2m+5M6lK2xzCc/tmbQJWqfLHRgWEGYrJ3y5mIbx2W1ysBLUI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 > Signed-off-by: Luis Chamberlain > --- > 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?