From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: Re: [PATCH v2 6/8] kvm tools: Add rwlock wrapper Date: Mon, 30 May 2011 13:05:34 +0300 Message-ID: <1306749934.14564.71.camel@lappy> References: <1306744247-26051-1-git-send-email-levinsasha928@gmail.com> <1306744247-26051-6-git-send-email-levinsasha928@gmail.com> <20110530084309.GH30513@elte.hu> <1306748069.14564.52.camel@lappy> <1306748796.14564.62.camel@lappy> <20110530095645.GC8461@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Pekka Enberg , kvm@vger.kernel.org, asias.hejun@gmail.com, gorcunov@gmail.com, prasadjoshi124@gmail.com, "Paul E. McKenney" To: Ingo Molnar Return-path: Received: from mail-ww0-f44.google.com ([74.125.82.44]:45660 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752105Ab1E3KGD (ORCPT ); Mon, 30 May 2011 06:06:03 -0400 Received: by wwa36 with SMTP id 36so3751751wwa.1 for ; Mon, 30 May 2011 03:06:02 -0700 (PDT) In-Reply-To: <20110530095645.GC8461@elte.hu> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, 2011-05-30 at 11:56 +0200, Ingo Molnar wrote: > * Sasha Levin wrote: > > > I'm just saying that we're limited to as many VCPU threads as we > > can create. br_read_lock() won't do anything on a non-VCPU thread, > > which makes it impossible to test it on non-VCPUs. > > btw., i wondered about that limit - don't we want to fix it? > > I mean, there's no fundamental reason why brlocks should do 'nothing' > in worker threads. In fact it's a subtle breakage waiting AFAICS. > Can they do anything useful without locking? I think we should work on integrating an RCU and changing brlocks to use that instead of focusing too much on the current implementation. This will also fix that limit you don't like :) > We should have enumeration for all threads that kvm starts, and that > we can use for a generic pause/resume facility. Can you see anything > that prevents that model? > Theres a difference between how you would pause a VCPU thread as opposed to a non-VCPU thread, other than that - no. We could use a thread manager. > Thanks, > > Ingo -- Sasha.