From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756473AbdKODU2 (ORCPT ); Tue, 14 Nov 2017 22:20:28 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:55876 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752957AbdKODUW (ORCPT ); Tue, 14 Nov 2017 22:20:22 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Kirill Tkhai Cc: Cong Wang , David Miller , vyasevic@redhat.com, kstewart@linuxfoundation.org, pombredanne@nexb.com, Vladislav Yasevich , mark.rutland@arm.com, Greg KH , Alexey Dobriyan , Florian Westphal , Nicolas Dichtel , roman.kapl@sysgo.com, Paul Moore , David Ahern , Daniel Borkmann , lucien xin , Matthias Schiffer , rshearma@brocade.com, LKML , Linux Kernel Network Developers , avagin@virtuozzo.com, gorcunov@virtuozzo.com References: <151066759055.14465.9783879083192000862.stgit@localhost.localdomain> <88152c11-a5b5-90f8-be46-99ed6c722064@virtuozzo.com> Date: Tue, 14 Nov 2017 21:19:50 -0600 In-Reply-To: <88152c11-a5b5-90f8-be46-99ed6c722064@virtuozzo.com> (Kirill Tkhai's message of "Tue, 14 Nov 2017 22:58:15 +0300") Message-ID: <87shdg8bzd.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1eEoFI-0001JI-C1;;;mid=<87shdg8bzd.fsf@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=75.170.119.32;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/MvwtGkRUaxXaWL3xy8875/HVcejyHR6A= X-SA-Exim-Connect-IP: 75.170.119.32 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.7 XMSubLong Long Subject * 0.0 TVD_RCVD_IP Message was received from an IP address * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.4755] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa02 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.0 T_TooManySym_03 6+ unique symbols in subject * 0.0 T_TooManySym_02 5+ unique symbols in subject X-Spam-DCC: XMission; sa02 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Kirill Tkhai X-Spam-Relay-Country: X-Spam-Timing: total 5331 ms - load_scoreonly_sql: 0.07 (0.0%), signal_user_changed: 3.3 (0.1%), b_tie_ro: 2.3 (0.0%), parse: 1.25 (0.0%), extract_message_metadata: 29 (0.5%), get_uri_detail_list: 2.9 (0.1%), tests_pri_-1000: 11 (0.2%), tests_pri_-950: 2.1 (0.0%), tests_pri_-900: 1.87 (0.0%), tests_pri_-400: 42 (0.8%), check_bayes: 40 (0.7%), b_tokenize: 15 (0.3%), b_tok_get_all: 9 (0.2%), b_comp_prob: 5 (0.1%), b_tok_touch_all: 6 (0.1%), b_finish: 0.87 (0.0%), tests_pri_0: 592 (11.1%), check_dkim_signature: 0.95 (0.0%), check_dkim_adsp: 5 (0.1%), tests_pri_500: 4642 (87.1%), poll_dns_idle: 4625 (86.8%), rewrite_mail: 0.00 (0.0%) Subject: Re: [PATCH] net: Convert net_mutex into rw_semaphore and down read it on net->init/->exit X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Kirill Tkhai writes: > On 14.11.2017 21:39, Cong Wang wrote: >> On Tue, Nov 14, 2017 at 5:53 AM, Kirill Tkhai wrote: >>> @@ -406,7 +406,7 @@ struct net *copy_net_ns(unsigned long flags, >>> >>> get_user_ns(user_ns); >>> >>> - rv = mutex_lock_killable(&net_mutex); >>> + rv = down_read_killable(&net_sem); >>> if (rv < 0) { >>> net_free(net); >>> dec_net_namespaces(ucounts); >>> @@ -421,7 +421,7 @@ struct net *copy_net_ns(unsigned long flags, >>> list_add_tail_rcu(&net->list, &net_namespace_list); >>> rtnl_unlock(); >>> } >>> - mutex_unlock(&net_mutex); >>> + up_read(&net_sem); >>> if (rv < 0) { >>> dec_net_namespaces(ucounts); >>> put_user_ns(user_ns); >>> @@ -446,7 +446,7 @@ static void cleanup_net(struct work_struct *work) >>> list_replace_init(&cleanup_list, &net_kill_list); >>> spin_unlock_irq(&cleanup_list_lock); >>> >>> - mutex_lock(&net_mutex); >>> + down_read(&net_sem); >>> >>> /* Don't let anyone else find us. */ >>> rtnl_lock(); >>> @@ -486,7 +486,7 @@ static void cleanup_net(struct work_struct *work) >>> list_for_each_entry_reverse(ops, &pernet_list, list) >>> ops_free_list(ops, &net_exit_list); >>> >>> - mutex_unlock(&net_mutex); >>> + up_read(&net_sem); >> >> After your patch setup_net() could run concurrently with cleanup_net(), >> given that ops_exit_list() is called on error path of setup_net() too, >> it means ops->exit() now could run concurrently if it doesn't have its >> own lock. Not sure if this breaks any existing user. > > Yes, there will be possible concurrent ops->init() for a net namespace, > and ops->exit() for another one. I hadn't found pernet operations, which > have a problem with that. If they exist, they are hidden and not clear seen. > The pernet operations in general do not touch someone else's memory. > If suddenly there is one, KASAN should show it after a while. Certainly the use of hash tables shared between multiple network namespaces would count. I don't rembmer how many of these we have but there used to be quite a few. Eric