From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753915Ab3CKRic (ORCPT ); Mon, 11 Mar 2013 13:38:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40939 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752462Ab3CKRib (ORCPT ); Mon, 11 Mar 2013 13:38:31 -0400 Date: Mon, 11 Mar 2013 18:36:25 +0100 From: Oleg Nesterov To: Andrew Morton , Thomas Gleixner Cc: Namhyung Kim , "Paul E. McKenney" , Peter Zijlstra , Rusty Russell , "Srivatsa S. Bhat" , linux-kernel@vger.kernel.org Subject: [PATCH 0/2] kthread: kill task_get_live_kthread() Message-ID: <20130311173625.GA13525@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 Hello. Imho, task_get_live_kthread() is very confusing and unneeded. 2a1d4460 copied get_task_struct() + "vfork_done != NULL" from kthread_stop(), but only kthread_stop() needs them both. It needs get_task_struct() because kthread_stop() can be used when the caller doesn't have a reference but we know that this thread can't exit itself. At the same time, if it can exit we do not need get_task_struct() (the caller must have a reference) but we need to ensure we do not use to_kthread(NULL) if it has exited. I think that kthread_park/unpark can simply use to_kthread(), but this series only removes get_task_struct() and keeps "alive" check. But the actual reason for this cleanup is that I do not understand why park/unpark abuse kthread.c. Thomas, can't we move kthread->parked/cpu to smpboot_thread_data and move all this code into kernel/smpboot.c? Just for example, why kthread() does __kthread_parkme() ? smpboot_thread_fn() can do this at the start. Or this would be wrong/undesirable by some reason? Oleg.