linux-kernel - Re: [PATCH v3 3/3] debugobjects: Reduce contention on pool lock in fill

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <90546c16-52e3-b92c-d99b-724278647809@huawei.com>
Date: Wed, 11 Sep 2024 17:04:19 +0800
From: "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To: Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner
	<tglx@...utronix.de>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] debugobjects: Reduce contention on pool lock in
 fill_pool()



On 2024/9/11 16:35, Zhen Lei wrote:
> If the conditions for starting fill are met, it means that all cores that
> call fill() later are blocked until the first core completes the fill
> operation.
> 
> Since it is low cost to move a set of free nodes from list obj_to_free
> into obj_pool, once it is necessary to fill, trying to move regardless
> of whether the context is preemptible. To reduce contention on pool
> lock, use atomic operation to test state. Only the first comer is allowed
> to try. If the last comer finds that someone is already trying, it will
> give up.
> 
> Scenarios that use allocated node filling can also be applied lockless
> mechanisms, but slightly different. The global list obj_to_free can only
> be operated exclusively by one core, while kmem_cache_zalloc() can be
> invoked by multiple cores simultaneously. Use atomic counting to mark how
> many cores are filling, to reduce atomic write conflicts during check. In
> principle, only the first comer is allowed to fill, but there is a very
> low probability that multiple comers may fill at the time.
> 
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>

Hi, Thomas:
  I was going to mark "Signed-off-by" as you. Because except for the
following line of changes, you wrote everything. But you're maintainer.
It doesn't seem good if I post a patch with your Signed-off-by. Please
feel free to change it, but do not forget to add "Reported-by" or
"Tested-by" for me.

@@ -174,14 +198,14 @@ static void fill_pool(void)
 				last = new;
 		}
 		if (!cnt)
-			return;
+			break;

-- 
Regards,
  Zhen Lei