From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Giacomo S." Subject: information about kernel locking issue - some other detail Date: Sun, 2 Jul 2006 10:22:22 +0200 Message-ID: <200607021022.22822.delleceste@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline To: netfilter-devel@lists.netfilter.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: netfilter-devel-bounces@lists.netfilter.org Errors-To: netfilter-devel-bounces@lists.netfilter.org List-Id: netfilter-devel.vger.kernel.org Sorry, i did not specify an important detail: this function is invoked by a series of other functions, the first of those is hooked tol the netfilter hooks. So, depending on the 'direction' of the flow (input, output, fwd), we are in user context (for output) or soft interrupt (in, fwd). >> Sorry, i forgot to explain better the reason why i used _bh version: in output hook the function should be running in user context. So it might be interrupted by softirq. I thought about using _irq version because hardware interrupts, such as those who could appear when disconnecting an ethernet cable, could interrupt my routine, which could be in softirq context or user context (output). Then they would change the data and when my routine restarted execution, it would look for an empty pointer. I thought that read_lock() was enough, but could read_lock() protect about writings in hard irq context? Am i wrong? Any suggestions? Subject: information about kernel locking issue Date: 13:55, sabato 1 luglio 2006 From: "Giacomo S." To: netfilter-devel@lists.netfilter.org Good morning. Some time ago i wrote a module in kernel space which does some filtering. While running `dhclient eth0' and plugging/unplugging the ethernet cable from the network card, kernel freezed saying the culprit was the following function (EIP is at get_ifaddr_by_name() ) : /* returns in *addr the internet address having the name ifname */ int get_ifaddr_by_name(const char *ifname, __u32 * addr) { struct net_device *pnet_device; struct in_device *pin_device; read_lock_bh(&dev_base_lock); pnet_device = dev_base; while (pnet_device != NULL) { if ((netif_running(pnet_device)) && (pnet_device->ip_ptr != NULL) && (strcmp(pnet_device->name, ifname) == 0)) { pin_device = (struct in_device *) pnet_device->ip_ptr; /* ifa_local: ifa_address is the remote point in ppp */ *addr = (pin_device->ifa_list->ifa_local); read_unlock_bh(&dev_base_lock); return 1; } pnet_device = pnet_device->next; } read_unlock_bh(&dev_base_lock); return -1; /* address not found! */ } What could be wrong? I think the problem is that read_lock_bh is not correct, perhaps i would need read_lock_irq instead?? Can anyone suggest if i am right. Thanks a lot Giacomo. -- Giacomo S. www.giacomos.it