From owner-freebsd-hackers@FreeBSD.ORG Tue Jan 8 06:34:06 2013 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 9648894D for ; Tue, 8 Jan 2013 06:34:06 +0000 (UTC) (envelope-from rsharpe@richardsharpe.com) Received: from zmail.servaris.com (zmail.servaris.com [107.6.51.160]) by mx1.freebsd.org (Postfix) with ESMTP id 4BA40D81 for ; Tue, 8 Jan 2013 06:34:06 +0000 (UTC) Received: (qmail 49904 invoked by uid 89); 8 Jan 2013 06:34:05 -0000 Received: from unknown (HELO ?192.168.2.23?) (rsharpe@richardsharpe.com@108.225.16.199) by mail.richardsharpe.com with ESMTPA; 8 Jan 2013 06:34:04 -0000 Subject: Re: Is it possible to block pending queued RealTime signals (AIO originating)? From: Richard Sharpe To: David Xu In-Reply-To: <50EB888A.2030802@freebsd.org> References: <1357608470.6752.22.camel@localhost.localdomain> <50EB888A.2030802@freebsd.org> Content-Type: text/plain; charset="UTF-8" Date: Mon, 07 Jan 2013 22:33:58 -0800 Message-ID: <1357626838.6752.27.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 (2.32.3-1.fc14) Content-Transfer-Encoding: 7bit Cc: freebsd-hackers@freebsd.org X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 Jan 2013 06:34:06 -0000 On Tue, 2013-01-08 at 10:46 +0800, David Xu wrote: > On 2013/01/08 09:27, Richard Sharpe wrote: > > Hi folks, > > > > I am running into a problem with AIO in Samba 3.6.x under FreeBSD 8.0 > > and I want to check if the assumptions made by the original coder are > > correct. > > > > Essentially, the code queues a number of AIO requests (up to 100) and > > specifies an RT signal to be sent upon completion with siginfo_t. > > > > These are placed into an array. > > > > The code assumes that when handling one of these signals, if it has > > already received N such siginfo_t structures, it can BLOCK further > > instances of the signal while these structures are drained by the main > > code in Samba. > > > > However, my debugging suggests that if a bunch of signals have already > > been queued, you cannot block those undelivered but already queued > > signals. > > > > I am certain that they are all being delivered to the main thread and > > that they keep coming despite the code trying to stop them at 64 (they > > get all the way up to the 100 that were queued.) > > > > Can someone confirm whether I have this correct or not? > > > > I am curious that how the code BLOCKs the signal in its signal handler ? > AFAIK, after signal handler returned, original signal mask is restored, > and re-enables the signal delivering, unless you change it in > ucontext.uc_sigmask. It does try to block the signals in the signal handler using the following code (in the signal handler): if (count+1 == TEVENT_SA_INFO_QUEUE_COUNT) { /* we've filled the info array - block this signal until these ones are delivered */ sigset_t set; sigemptyset(&set); sigaddset(&set, signum); sigprocmask(SIG_BLOCK, &set, NULL); However, I also added pthread_sigmask with the same parameters to see if that made any difference and it seemed not to.