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[2003:c0:df04:c500:f68c:50ff:fe53:cb63]) by smtp.gmail.com with ESMTPSA id h12sm18218724wre.14.2019.05.22.10.58.01 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 22 May 2019 10:58:02 -0700 (PDT) Date: Wed, 22 May 2019 19:57:59 +0200 From: =?utf-8?B?TcOhdMOp?= Eckl To: Amit Kumar Subject: Re: Unable to understand a piece of code Message-ID: <20190522175759.4ganjslc6mooxrcp@sch.bme.hu> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-Mailman-Approved-At: Wed, 22 May 2019 16:32:37 -0400 Cc: linux-newbie@vger.kernel.org, Kernel Newbies X-BeenThere: kernelnewbies@kernelnewbies.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Errors-To: kernelnewbies-bounces@kernelnewbies.org On Mon, May 20, 2019 at 05:37:41AM +0530, Amit Kumar wrote: > HI, > = > mm/slub.c: line 3973 > int __kmem_cache_shrink(struct kmem_cache *s) > { > int node; > int i; > struct kmem_cache_node *n; > struct page *page; > struct page *t; > struct list_head discard; > struct list_head promote[SHRINK_PROMOTE_MAX]; > unsigned long flags; > int ret =3D 0; > = > flush_all(s); > for_each_kmem_cache_node(s, node, n) { > = > How uninitialized variable node is being used in macro for_each_kmem_cach= e_node? > = > node is a local variable with no extern and not initialized. > = > mm/slab.h: line 490 > #define for_each_kmem_cache_node(__s, __node, __n) \ > for (__node =3D 0; __node < nr_node_ids; __node++) \ > if ((__n =3D get_node(__s, __node))) > = > As we see for loop is based on node. Hi, This sentence is almost correct. The for loop is *not based* on node but *u= ses* the node variable. If you check, __node gets initialised to 0 at the beginn= ing of the for loop. So whatever you use that macro with will be initialised to 0 = at the beginning of the for loop. Bests, M=E1t=E9 > = > Thanks in advance. > = > Regards, > Amit Kumar _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies