Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754169AbaDNCuU (ORCPT ); Sun, 13 Apr 2014 22:50:20 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:33971 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750770AbaDNCuS (ORCPT ); Sun, 13 Apr 2014 22:50:18 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v2.2.3 X-SHieldMailCheckerPolicyVersion: FJ-ISEC-20140219-2 Message-ID: <534B4CB5.9010401@jp.fujitsu.com> Date: Mon, 14 Apr 2014 11:49:25 +0900 From: Takao Indoh User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: rusty@rustcorp.com.au CC: rostedt@goodmis.org, masami.hiramatsu.pt@hitachi.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] module: Introduce MODULE_STATE_COMING_FINAL to avoid ftrace warning References: <1396425266-3128-1-git-send-email-indou.takao@jp.fujitsu.com> In-Reply-To: <1396425266-3128-1-git-send-email-indou.takao@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ping, any comments? (2014/04/02 16:54), Takao Indoh wrote: > This patch adds new module state MODULE_STATE_COMING_FINAL to avoid > ftrace waring message when loading two modules simultaneously. > > The original patch was written by Steven Rostedt, see below. > https://lkml.org/lkml/2014/3/24/242 > > Ftrace waring message below is got when insmod two modules almost at the > same time and at least one of them uses register_kprobe() in its > module_init. > > [ 409.337936] ------------[ cut here ]------------ > [ 409.337945] WARNING: CPU: 12 PID: 10028 at /mnt/repos/linux/kernel/trace/ftrace.c:1716 ftrace_bug+0x206/0x270() > (snip) > [ 409.337983] Call Trace: > [ 409.337990] [] dump_stack+0x45/0x56 > [ 409.337993] [] warn_slowpath_common+0x7d/0xa0 > [ 409.337997] [] ? 0xffffffffa0363fff > [ 409.337999] [] warn_slowpath_null+0x1a/0x20 > [ 409.338001] [] ftrace_bug+0x206/0x270 > [ 409.338004] [] ? 0xffffffffa0363fff > [ 409.338006] [] ftrace_process_locs+0x32e/0x710 > [ 409.338008] [] ftrace_module_notify_enter+0x96/0xf0 > [ 409.338012] [] notifier_call_chain+0x4c/0x70 > [ 409.338018] [] __blocking_notifier_call_chain+0x4d/0x70 > [ 409.338020] [] blocking_notifier_call_chain+0x16/0x20 > [ 409.338026] [] load_module+0x1f54/0x25d0 > [ 409.338028] [] ? store_uevent+0x40/0x40 > [ 409.338031] [] SyS_finit_module+0x86/0xb0 > [ 409.338036] [] system_call_fastpath+0x16/0x1b > [ 409.338037] ---[ end trace e7e27c36e7a65831 ]--- > [ 409.338040] ftrace faulted on writing [] handler_pre+0x0/0x10 [test2] > > This is the sequence when this problem occurs. > > > init_module > load_module > do_init_module > do_one_initcall > (module_init) > register_kprobe > arm_kprobe > arm_kprobe_ftrace > register_ftrace_function > mutex_lock(&ftrace_lock) ------------------- (1) > ftrace_startup > ftrace_startup_enable > ftrace_run_update_code > ftrace_arch_code_modify_post_process > set_all_modules_text_ro ------------ (2) > mutex_unlock(&ftrace_lock) ----------------- (3) > > > init_module > load_module > do_init_module > blocking_notifier_call_chain > ftrace_module_notify_enter > ftrace_init_module > ftrace_process_locs > mutex_lock(&ftrace_lock) ------------------------ (4) > ftrace_update_code > __ftrace_replace_code > ftrace_make_nop > ftrace_modify_code_direct > do_ftrace_mod_code > probe_kernel_write -------------------- (5) > > o Module A gets ftrace_lock at (1) > o Module B also tries to get ftrace_lock at (4) somewhat late, and waits > here because module A got it. > o Module A sets all modules text to ReadOnly at (2), and then release > ftrace_lock at (3) > o Module B wakes up and tries to rewrite its text at (5), but it fails > because it is already changed to RO at (2) by modules A. The ftrace > waring message is outputted. > > This patch introduces MODULE_STATE_COMING_FINAL which means that the > module is ready to be changed to ReadOnly. By this, the modules B is not > change to RO at (2) because its state is still MODULE_STATE_COMING, so > this warning message is avoided. Module B is changed to RO in the > do_init_module() after comes back from notifier. > > Signed-off-by: Takao Indoh > --- > include/linux/module.h | 9 +++++---- > kernel/module.c | 13 ++++++++++++- > 2 files changed, 17 insertions(+), 5 deletions(-) > > diff --git a/include/linux/module.h b/include/linux/module.h > index eaf60ff..32f4481 100644 > --- a/include/linux/module.h > +++ b/include/linux/module.h > @@ -207,10 +207,11 @@ struct module_use { > }; > > enum module_state { > - MODULE_STATE_LIVE, /* Normal state. */ > - MODULE_STATE_COMING, /* Full formed, running module_init. */ > - MODULE_STATE_GOING, /* Going away. */ > - MODULE_STATE_UNFORMED, /* Still setting it up. */ > + MODULE_STATE_LIVE, /* Normal state. */ > + MODULE_STATE_COMING, /* Full formed, running module_init. */ > + MODULE_STATE_COMING_FINAL, /* Ready to be changed to read only. */ > + MODULE_STATE_GOING, /* Going away. */ > + MODULE_STATE_UNFORMED, /* Still setting it up. */ > }; > > /** > diff --git a/kernel/module.c b/kernel/module.c > index 8dc7f5e..94b9f91 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -1033,6 +1033,9 @@ static ssize_t show_initstate(struct module_attribute *mattr, > case MODULE_STATE_COMING: > state = "coming"; > break; > + case MODULE_STATE_COMING_FINAL: > + state = "coming_final"; > + break; > case MODULE_STATE_GOING: > state = "going"; > break; > @@ -1805,7 +1808,8 @@ void set_all_modules_text_ro(void) > > mutex_lock(&module_mutex); > list_for_each_entry_rcu(mod, &modules, list) { > - if (mod->state == MODULE_STATE_UNFORMED) > + if (mod->state == MODULE_STATE_UNFORMED || > + mod->state == MODULE_STATE_COMING) > continue; > if ((mod->module_core) && (mod->core_text_size)) { > set_page_attributes(mod->module_core, > @@ -3024,6 +3028,13 @@ static int do_init_module(struct module *mod) > blocking_notifier_call_chain(&module_notify_list, > MODULE_STATE_COMING, mod); > > + /* > + * This module must not be changed by set_all_modules_text_ro() > + * until we get here. Otherwise notifiers that change text > + * (like ftrace does) will break. > + */ > + mod->state = MODULE_STATE_COMING_FINAL; > + > /* Set RO and NX regions for core */ > set_section_ro_nx(mod->module_core, > mod->core_text_size, > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/