From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga07-in.huawei.com (szxga07-in.huawei.com [45.249.212.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DEBCA1A4E8D for ; Tue, 3 Sep 2024 02:16:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.35 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725329793; cv=none; b=UY/zJyXR3sfIZbXDEla674oghAeff1ImnemxcO3AttZchIxJUTMbVmnT/xDqyUepAJb3Yno+cPATcI3b198+GnP4G+2cbAMtUwX1uO3CF40djf3I4Zk74KwWwLNnfAR3lh4QQ81FjSFtZddsOkgtYCnJUGqEvEJs/Ubdw62s3dg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725329793; c=relaxed/simple; bh=0sttYggSdPPS9lvkKhqI4BlH3HInIDXQnO+wAWS3/lI=; h=Subject:To:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=MfZkQFqEjOJe8uHj8HHy6pUDuv00NKH4YIjw1mk2cqHbJ0gQ113Xs1KV8BY/+71izNKDP0e+DmpvDjcNbj+RhxlLdM+4DYt4b5r83boM+U3dIAbelcVXZ8ToknYPwbpEoQgcl7SBTp8iYi7fvgeIGKj/DzFsfPO2BaNsBmP21GU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.35 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.44]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4WyTkV0LQFz1S9bC; Tue, 3 Sep 2024 10:16:02 +0800 (CST) Received: from dggpemf100006.china.huawei.com (unknown [7.185.36.228]) by mail.maildlp.com (Postfix) with ESMTPS id 3C47E14022E; Tue, 3 Sep 2024 10:16:21 +0800 (CST) Received: from [10.174.178.55] (10.174.178.55) by dggpemf100006.china.huawei.com (7.185.36.228) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 3 Sep 2024 10:16:20 +0800 Subject: Re: [PATCH 1/5] debugobjects: Fix the misuse of global variables in fill_pool() To: Thomas Gleixner , Andrew Morton , References: <20240902140532.2028-1-thunder.leizhen@huawei.com> <20240902140532.2028-2-thunder.leizhen@huawei.com> <87mskq58l5.ffs@tglx> From: "Leizhen (ThunderTown)" Message-ID: <13d2be50-4a52-7cf0-8325-65435ad47a62@huawei.com> Date: Tue, 3 Sep 2024 10:16:20 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <87mskq58l5.ffs@tglx> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemf100006.china.huawei.com (7.185.36.228) On 2024/9/3 0:22, Thomas Gleixner wrote: > On Mon, Sep 02 2024 at 22:05, Zhen Lei wrote: > >> The global variable 'obj_pool_min_free' records the lowest historical >> value of the number of nodes in the global list 'obj_pool', instead of >> being used as the lowest threshold value. This may be a mistake and > > Maybe? It's either a bug or not. Yes, it's a bug, but I'm just learning this module, so I'm not confident. > >> should be replaced with variable 'debug_objects_pool_min_level'. > > And if it's a bug then it has to be replaced. OK, I will update the commit message in V2. > > This misses another minor issue: > > static int obj_pool_min_free = ODEBUG_POOL_SIZE; > > static int __data_racy debug_objects_pool_min_level __read_mostly > = ODEBUG_POOL_MIN_LEVEL; > > As debug_objects_pool_min_level is the minimum level to keep around and > obj_pool_min_free is a statistics mechanism, __data_racy is misplaced > too. The variables should swap their position, because > debug_objects_pool_min_level is functional, but obj_pool_min_free is > pure stats. > > Also debug_objects_pool_min_level and debug_objects_pool_size should > be __ro_after_init. OK, How about modifying it like this? I further removed the __data_racy from debug_objects_pool_min_level and debug_objects_pool_size, because __ro_after_init. diff --git a/lib/debugobjects.c b/lib/debugobjects.c index d3845705db955fa..816d3d968cd9f14 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -70,7 +70,8 @@ static HLIST_HEAD(obj_to_free); * made at debug_stats_show(). Both obj_pool_min_free and obj_pool_max_used * can be off. */ -static int obj_pool_min_free = ODEBUG_POOL_SIZE; +static int __ro_after_init debug_objects_pool_size = ODEBUG_POOL_SIZE; +static int __ro_after_init debug_objects_pool_min_level = ODEBUG_POOL_MIN_LEVEL; static int obj_pool_free = ODEBUG_POOL_SIZE; static int obj_pool_used; static int obj_pool_max_used; @@ -84,10 +85,7 @@ static int __data_racy debug_objects_fixups __read_mostly; static int __data_racy debug_objects_warnings __read_mostly; static int __data_racy debug_objects_enabled __read_mostly = CONFIG_DEBUG_OBJECTS_ENABLE_DEFAULT; -static int __data_racy debug_objects_pool_size __read_mostly - = ODEBUG_POOL_SIZE; -static int __data_racy debug_objects_pool_min_level __read_mostly - = ODEBUG_POOL_MIN_LEVEL; +static int __data_racy obj_pool_min_free = ODEBUG_POOL_SIZE; static const struct debug_obj_descr *descr_test __read_mostly; static struct kmem_cache *obj_cache __ro_after_init; > >> Fixes: d26bf5056fc0 ("debugobjects: Reduce number of pool_lock acquisitions in fill_pool()") >> Fixes: 36c4ead6f6df ("debugobjects: Add global free list and the counter") > > Nice detective work! > > Thanks, > > tglx > . > -- Regards, Zhen Lei