From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) (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 167C41A4E6B for ; Tue, 3 Sep 2024 03:22:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725333777; cv=none; b=BxS5Or5CXwVpNIDZNnYKTAXCuGbZBq3I3Zl2yRSMBFTq3Dr4SPgQC6HbFYYmiXqITg/z50DSVzh9kvliKZFVwyFgcf8S3/e90mf27oYDYfqD+4lBDEx5MR8bM+usK0iHLvT3CeLfxfFK01SUwoZR1mabtGDFGyrkhiPTcC2Z5RQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725333777; c=relaxed/simple; bh=UNFiPx1a8ps39k17drwmAYk8T7SbMM8+ejVqOvUINYk=; h=Subject:From:To:References:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=pzXZhWLFyoWQRqr7njm1ctarPL1wQaX5gG7ru+KCQSCy9bF+IG7sRE+XdTDs+pnmJMQHFS5A+qJFt2k8Ctp9c4+42bkzoIZoKN7L/qgRx+2NZrI4WRZIWgiHuxpWjPMGwHQ5f2ToN3WFosOCeo5GsUK53rAR1sy1BcOo0bKXc2g= 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=45.249.212.187 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 [172.19.163.174]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4WyWBw0Qx0zyRQ5; Tue, 3 Sep 2024 11:22:16 +0800 (CST) Received: from dggpemf100006.china.huawei.com (unknown [7.185.36.228]) by mail.maildlp.com (Postfix) with ESMTPS id AB08C140258; Tue, 3 Sep 2024 11:22:52 +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 11:22:52 +0800 Subject: Re: [PATCH 1/5] debugobjects: Fix the misuse of global variables in fill_pool() From: "Leizhen (ThunderTown)" To: Thomas Gleixner , Andrew Morton , References: <20240902140532.2028-1-thunder.leizhen@huawei.com> <20240902140532.2028-2-thunder.leizhen@huawei.com> <87mskq58l5.ffs@tglx> <13d2be50-4a52-7cf0-8325-65435ad47a62@huawei.com> Message-ID: <3bb35c94-dd54-33d4-b7ac-64f0d2b77c07@huawei.com> Date: Tue, 3 Sep 2024 11:22:51 +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: <13d2be50-4a52-7cf0-8325-65435ad47a62@huawei.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemf100006.china.huawei.com (7.185.36.228) On 2024/9/3 10:16, Leizhen (ThunderTown) wrote: > > > 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. This principle covers a large number of variables. It should be sorted by the variable name before. It's better not to change the position this time. >> >> 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