Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751733AbbEDOe5 (ORCPT ); Mon, 4 May 2015 10:34:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40329 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750863AbbEDOet (ORCPT ); Mon, 4 May 2015 10:34:49 -0400 Date: Mon, 4 May 2015 16:34:23 +0200 From: Oleg Nesterov To: Jiri Slaby Cc: live-patching@vger.kernel.org, jpoimboe@redhat.com, sjenning@redhat.com, jkosina@suse.cz, vojtech@suse.cz, mingo@redhat.com, linux-kernel@vger.kernel.org, Miroslav Benes , Peter Zijlstra Subject: Re: [RFC kgr on klp 9/9] livepatch: send a fake signal to all tasks Message-ID: <20150504143423.GA25809@redhat.com> References: <1430739625-4658-1-git-send-email-jslaby@suse.cz> <1430739625-4658-9-git-send-email-jslaby@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1430739625-4658-9-git-send-email-jslaby@suse.cz> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1960 Lines: 61 Well, I can't really comment this change because I didn't see other changes, and I do not know what klp_kgraft_task_in_progress() means... On 05/04, Jiri Slaby wrote: > > Luckily we can force the task to do that by sending it a fake signal, But note that signal_wake_up(0) won't wake the stopped/traced tasks up. > +static void klp_kgraft_send_fake_signal(void) > +{ > + struct task_struct *p; > + unsigned long flags; > + > + read_lock(&tasklist_lock); > + for_each_process(p) { Only the group leader can be klp_kgraft_task_in_progress? Looks like you need for_each_process_thread()... > + /* > + * send fake signal to all non-kthread processes which are still > + * not migrated > + */ > + if (!(p->flags & PF_KTHREAD) && So this can miss the execing kernel thread, I do not know if this is correct or not. PF_KTHREAD is cleared in flush_old_exec(). > + klp_kgraft_task_in_progress(p) && > + lock_task_sighand(p, &flags)) { No need for lock_task_sighand(). Just spin_lock_irq(p->sighand->siglock). tasklist_lock + for_each_process guarantees that "p" has a valid ->sighand. > + signal_wake_up(p, 0); To remind, this won't wakeup a TASK_STOPPED/TRACED thread. > void recalc_sigpending(void) > { > - if (!recalc_sigpending_tsk(current) && !freezing(current)) > + if (!recalc_sigpending_tsk(current) && !freezing(current) && > + !klp_kgraft_task_in_progress(current)) > clear_thread_flag(TIF_SIGPENDING); It is not clear from this patch when TIF_SIGPENDING will be cleared. I assume other changes add some hooks into do_notify_resume/get_signal paths, otherwise a klp_kgraft_task_in_progress() will spin until klp_kgraft_task_in_progress(current) becomes "false". Oleg. -- 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/