From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: [RFC PATCH 09/18] kthread: Make it easier to correctly sleep in iterant kthreads Date: Mon, 8 Jun 2015 13:48:10 -0400 Message-ID: <20150608134810.3abd862b@gandalf.local.home> References: <1433516477-5153-1-git-send-email-pmladek@suse.cz> <1433516477-5153-10-git-send-email-pmladek@suse.cz> <20150605161021.GJ19282@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150605161021.GJ19282-ndre7Fmf5hadTX5a5knrm8zTDFooKrT+cvkQGrU6aU0@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Peter Zijlstra Cc: Petr Mladek , Andrew Morton , Oleg Nesterov , Tejun Heo , Ingo Molnar , Richard Weinberger , David Woodhouse , linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Trond Myklebust , Anna Schumaker , linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Chris Mason , "Paul E. McKenney" , Thomas Gleixner , Linus Torvalds , Jiri Kosina , Borislav Petkov , Michal Hocko , live-patching-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org On Fri, 5 Jun 2015 18:10:21 +0200 Peter Zijlstra wrote: > On Fri, Jun 05, 2015 at 05:01:08PM +0200, Petr Mladek wrote: > > Many kthreads go into an interruptible sleep when there is nothing > > to do. They should check if anyone did not requested the kthread > > to terminate, freeze, or park in the meantime. It is easy to do > > it a wrong way. > > INTERRUPTIBLE is the wrong state to idle in for kthreads, use > TASK_IDLE. > > --- > > commit 80ed87c8a9ca0cad7ca66cf3bbdfb17559a66dcf > Author: Peter Zijlstra > Date: Fri May 8 14:23:45 2015 +0200 > > sched/wait: Introduce TASK_NOLOAD and TASK_IDLE > > Currently people use TASK_INTERRUPTIBLE to idle kthreads and wait for > 'work' because TASK_UNINTERRUPTIBLE contributes to the loadavg. Having > all idle kthreads contribute to the loadavg is somewhat silly. Not to mention, tasks in TASK_UNINTERRUPTIBLE state for too long will trigger hung task detection. > > Now mostly this works OK, because kthreads have all their signals > masked. However there's a few sites where this is causing problems and > TASK_UNINTERRUPTIBLE should be used, except for that loadavg issue. > > This patch adds TASK_NOLOAD which, when combined with > TASK_UNINTERRUPTIBLE avoids the loadavg accounting. > > As most of imagined usage sites are loops where a thread wants to > idle, waiting for work, a helper TASK_IDLE is introduced. > > Signed-off-by: Peter Zijlstra (Intel) Acked-by: Steven Rostedt -- Steve > Cc: Julian Anastasov > Cc: Linus Torvalds > Cc: NeilBrown > Cc: Oleg Nesterov > Cc: Peter Zijlstra > Cc: Thomas Gleixner > Signed-off-by: Ingo Molnar > > diff --git a/include/linux/sched.h b/include/linux/sched.h