From owner-svn-src-projects@FreeBSD.ORG Mon Jul 30 20:52:18 2012 Return-Path: Delivered-To: svn-src-projects@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 07574106564A; Mon, 30 Jul 2012 20:52:18 +0000 (UTC) (envelope-from asmrookie@gmail.com) Received: from mail-lb0-f182.google.com (mail-lb0-f182.google.com [209.85.217.182]) by mx1.freebsd.org (Postfix) with ESMTP id C95C58FC18; Mon, 30 Jul 2012 20:52:16 +0000 (UTC) Received: by lbon10 with SMTP id n10so4516964lbo.13 for ; Mon, 30 Jul 2012 13:52:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:reply-to:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; bh=LZFIVlKXGEPIQB/2xDJ9P53r/HLeW4b/HUpLVk9caSk=; b=iOM0KBcUo3SAqXe2Q4uA+0yXa1ClkmkDHgKu6oKxUaSKQC4m2J3QTAKJi9HqT9Dyc6 uekj/GE+OxiAdsu4uAMLrfUu4+rXmibGTkWtOoRSJy7Jc3RA5/5P3BgW4e1LsH1jD7fy 269oSdpXX4Wt4x0f+pZmtlbt4JuFx/vc4yv+X+djadUEUb7/0c4h3CMKmd4MyPQVJCrw DU83uEPHpwPP6yimHFPetWH1bZ7ShejHamXDv4gzWNgVTVsc2SbYH6vkLPovujudSxMS Byt6WAD6KnGHe8XrRi34GFfv6lqdWDTo+0Iozd3MT7c6KZ5SkRezlDt2nB9Zw7btWyGC Jqlg== MIME-Version: 1.0 Received: by 10.152.144.163 with SMTP id sn3mr5256844lab.37.1343681534715; Mon, 30 Jul 2012 13:52:14 -0700 (PDT) Sender: asmrookie@gmail.com Received: by 10.112.27.65 with HTTP; Mon, 30 Jul 2012 13:52:14 -0700 (PDT) In-Reply-To: <201207301149.43458.jhb@freebsd.org> References: <201207301350.q6UDobCI099069@svn.freebsd.org> <20120730143943.GY2676@deviant.kiev.zoral.com.ua> <201207301149.43458.jhb@freebsd.org> Date: Mon, 30 Jul 2012 21:52:14 +0100 X-Google-Sender-Auth: XlmMThVZYWj6zLrPNFfLaxj76gk Message-ID: From: Attilio Rao To: John Baldwin Content-Type: text/plain; charset=UTF-8 Cc: Konstantin Belousov , Davide Italiano , src-committers@freebsd.org, svn-src-projects@freebsd.org Subject: Re: svn commit: r238907 - projects/calloutng/sys/kern X-BeenThere: svn-src-projects@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: attilio@FreeBSD.org List-Id: "SVN commit messages for the src " projects" tree" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 30 Jul 2012 20:52:18 -0000 On Mon, Jul 30, 2012 at 4:49 PM, John Baldwin wrote: > On Monday, July 30, 2012 10:39:43 am Konstantin Belousov wrote: >> On Mon, Jul 30, 2012 at 03:24:26PM +0100, Attilio Rao wrote: >> > On 7/30/12, Davide Italiano wrote: >> > > On Mon, Jul 30, 2012 at 4:02 PM, Attilio Rao > wrote: >> > > Thanks for the comment, Attilio. >> > > Yes, it's exactly what you thought. If direct flag is equal to one >> > > you're sure you're processing a callout which runs directly from >> > > hardware interrupt context. In this case, the running thread cannot >> > > sleep and it's likely you have TDP_NOSLEEPING flags set, failing the >> > > KASSERT() in THREAD_NO_SLEEPING() and leading to panic if kernel is >> > > compiled with INVARIANTS. >> > > In case you're running from SWI context (direct equals to zero) code >> > > remains the same as before. >> > > I think what I'm doing works due the assumption thread running never >> > > sleeps. Do you suggest some other way to handle this? >> > >> > Possibly the quicker way to do this is to have a way to deal with the >> > TDP_NOSLEEPING flag in recursed way, thus implement the same logic as >> > VFS_LOCK_GIANT() does, for example. >> > You will need to change the few callers of THREAD_NO_SLEEPING(), but >> > the patch should be no longer than 10/15 lines. >> >> There are already curthread_pflags_set/restore KPI designed exactly to > handle >> nested private thread flags. >> >> Also, I wonder, should you assert somehow that direct dispatch cannot block >> as well ? > > Hmm, I have a nested TDP_NOSLEEPING already (need it to fix an issue in > rmlocks). It uses a count though as the flag is set during rm_rlock() and > released during rm_runlock(). I don't think it could use a set/restore KPI as > there is no good place to store the state. Our stock rmlocks don't seem to use TDP_NOSLEEPING/THREAD_NO_SLEEPING so I'm not entirely sure about the case you were trying to fix, can you show the patch? Thanks, Attilio -- Peace can only be achieved by understanding - A. Einstein