From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756217AbdIHOfo (ORCPT ); Fri, 8 Sep 2017 10:35:44 -0400 Received: from mail-qk0-f193.google.com ([209.85.220.193]:36101 "EHLO mail-qk0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755563AbdIHOfl (ORCPT ); Fri, 8 Sep 2017 10:35:41 -0400 X-Google-Smtp-Source: AOwi7QB+rF2NNqAgzDcLBvWNVgwZgHQ4Bz9PIQNzr5q0F20ZmR3rU8iW/hFTsQBs8pM/ChqTg5CEkA== Date: Fri, 8 Sep 2017 07:35:37 -0700 From: Tejun Heo To: Shaohua Li Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, lizefan@huawei.com, tglx@linutronix.de, kernel-team@fb.com, axboe@kernel.dk, Shaohua Li Subject: Re: [PATCH 1/3] kthread: add a mechanism to store cgroup info Message-ID: <20170908143537.GW1774378@devbig577.frc2.facebook.com> References: <9d25e5bed5ef2fad5f8a817e293f0d93e3b329c2.1504748195.git.shli@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9d25e5bed5ef2fad5f8a817e293f0d93e3b329c2.1504748195.git.shli@fb.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Wed, Sep 06, 2017 at 07:00:51PM -0700, Shaohua Li wrote: > +#ifdef CONFIG_CGROUPS > +void kthread_set_orig_css(struct cgroup_subsys_state *css); > +struct cgroup_subsys_state *kthread_get_orig_css(void); > +void kthread_reset_orig_css(void); * It's a bit weird to associate a kthread with a css without being specific. If what's needed is a generic association (this kthread is temporarily servicing this cgroup), it should be associated with the cgroup. But, I think it'd be better to make it specific instead - ie. kthread_set_io_css(). * Do we need the reset function to be separate? Can't we just clear it when the set function is called with NULL css? * For the accessor, can we do sth like kthread_orig_css() (or kthread_io_css())? "get" is overloaded between set/get and get/put, so it can get confusing. > diff --git a/include/linux/sched.h b/include/linux/sched.h > index c05ac5f..ab2295d 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1276,6 +1276,7 @@ extern struct pid *cad_pid; > #define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */ > #define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_allowed */ > #define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */ > +#define PF_KTHREAD_HAS_CSS 0x10000000 /* kthread has css info attached */ Do we need a separate flag for this? kthreads already have PF_KTHREAD set. I'm not sure why we'd need another flag. Once we know it's a kthread, we can just access its css pointer field, right? Thanks. -- tejun