From owner-freebsd-current@FreeBSD.ORG Mon Jan 18 07:05:06 2010 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5D9C3106566B; Mon, 18 Jan 2010 07:05:06 +0000 (UTC) (envelope-from okuno.kohji@jp.panasonic.com) Received: from smtp.mei.co.jp (smtp.mei.co.jp [133.183.100.20]) by mx1.freebsd.org (Postfix) with ESMTP id 037888FC16; Mon, 18 Jan 2010 07:05:05 +0000 (UTC) Received: from mail-gw.jp.panasonic.com ([157.8.1.145]) by smtp.mei.co.jp (8.12.11.20060614/3.7W/kc-maile14) with ESMTP id o0I754Yc027066; Mon, 18 Jan 2010 16:05:04 +0900 (JST) Received: from epochmail.jp.panasonic.com (localhost [127.0.0.1]) by mail.jp.panasonic.com (8.11.6p2/3.7W/kc-maili06) with ESMTP id o0I754116469; Mon, 18 Jan 2010 16:05:04 +0900 (JST) Received: by epochmail.jp.panasonic.com (8.12.11.20060308/3.7W/somla2) id o0I753v8009257; Mon, 18 Jan 2010 16:05:03 +0900 (JST) Received: from localhost by somla2.jp.panasonic.com (8.12.11.20060308/3.7W) with ESMTP id o0I74wVH008904; Mon, 18 Jan 2010 16:04:58 +0900 (JST) Date: Mon, 18 Jan 2010 16:04:56 +0900 (JST) Message-Id: <20100118.160456.519459540419521301.okuno.kohji@jp.panasonic.com> To: attilio@freebsd.org From: Kohji Okuno In-Reply-To: <20100118.155352.59640143160034670.okuno.kohji@jp.panasonic.com> References: <20100117.152835.119882392487126976.okuno.kohji@jp.panasonic.com> <3bbf2fe11001171858o4568fe38l9b2db54ec9856b50@mail.gmail.com> <20100118.155352.59640143160034670.okuno.kohji@jp.panasonic.com> Organization: Panasonic Corporation X-Mailer: Mew version 6.3 on Emacs 23.1 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: jroberson@jroberson.net, freebsd-current@freebsd.org, okuno.kohji@jp.panasonic.com Subject: Re: Bug about sched_4bsd? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 18 Jan 2010 07:05:06 -0000 Hello, I have a question. The sleeping thread (on turnstile or on sleepque) can set sched_lock to td_lock, kernel are allowed? Best regards, Kohji Okuno. > Hello, > > Thank you, Attilio. > I checked your patch. I think that your patch is better. > I tested the patch quickly, and I think it's OK. > # This probrem does not occur easily :-< > > > What do you think about maybe_resched()? > I have never experienced about maybe_resched(), but I think that the > race condition may occur. > > <> > sched_4bsd.c: maybe_resched() > sched_4bsd.c: resetpriority_thread() > sched_4bsd.c: sched_nice() get thread_lock(td) > kern_resource.c: donice() > kern_resource.c: setpriority() get PROC_LOCK() > > static void > maybe_resched(struct thread *td) > { > THREAD_LOCK_ASSERT(td, MA_OWNED); > if (td->td_priority < curthread->td_priority) > curthread->td_flags |= TDF_NEEDRESCHED; > } > > I think, when td->td_lock is not &sched_lock, curthread->td_lock is > not locked in maybe_resched(). > > Best regards, > Kohji Okuno. > > From: Attilio Rao > Subject: Re: Bug about sched_4bsd? > Date: Mon, 18 Jan 2010 03:58:41 +0100 > Message-ID: <3bbf2fe11001171858o4568fe38l9b2db54ec9856b50@mail.gmail.com> > >> 2010/1/17 Kohji Okuno : >>> Hello, >>> >>> Could you check sched_4bsd.patch, please? >> >> I think, instead, that what needs to happen is to have sched_switch() >> to do a lock handover from sleepq/turnstile spinlock to schedlock. >> That way, if threads are willing to contest on td_lock they will be >> still inhibited. >> I'm not sure if this patch breaks any invariant, if you may test I >> would appreciate: >> http://www.freebsd.org/~attilio/sched_4bsd_schedlock.diff >> >> Reviews and comments are appreciated. >> BTW, nice catch. >> >> Attilio >> >> >> -- >> Peace can only be achieved by understanding - A. Einstein >> _______________________________________________ >> freebsd-current@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-current >> To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" > > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org"