From owner-freebsd-dtrace@freebsd.org Wed May 11 16:46:00 2016 Return-Path: Delivered-To: freebsd-dtrace@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E3AC2B37E6F for ; Wed, 11 May 2016 16:46:00 +0000 (UTC) (envelope-from markjdb@gmail.com) Received: from mail-pa0-x22a.google.com (mail-pa0-x22a.google.com [IPv6:2607:f8b0:400e:c03::22a]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id B5A191086 for ; Wed, 11 May 2016 16:46:00 +0000 (UTC) (envelope-from markjdb@gmail.com) Received: by mail-pa0-x22a.google.com with SMTP id r5so20172403pag.1 for ; Wed, 11 May 2016 09:46:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=jFF5THEWIMtCmXWVd/HEcMDwH0IheXWudW3vHBRM7RE=; b=AkEPHR/6hgLuCCp/ZzgelAmfsp+SJY2N58e3KECuB+9YWFGH3ccCY9zDLd+zKqfXrm YTdHGH/lFB5KoLA/8JwVqszdHOr7jVjOEFbfxV+fViVowWdThRfiJtotnOODiKKYUe89 TA2ycAfpQW0OaPZZ/KU28+rnR5X7t9pXpOcyPWLj1EOn99CL6Ujh5uAST3mSRBbliX28 r2Zrk7Ua2KTjtstOnQBm4fryhR8tFjcPpCqd9kYliMYYYK9/oURIgq6dEW/jTVOGZ3dM ockknaLnEtaRfzuOUaeObGvjAcjT1UIGOeCUXDooJdf8ZtABOEvDgMccJ8JihaOluck/ dSTQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=jFF5THEWIMtCmXWVd/HEcMDwH0IheXWudW3vHBRM7RE=; b=LK9CCjftR8QdstefUNRoYtFzarq2lE8K6aZWdfm9XFwfGg9FMKl+9xhRkxQn6L0TxA OSCwL2QudlnXu+UC9xFTr8c2SwA5LvZdexTitys4Zh/+R1zS4p0zwzGjpakAK0mwOGKU 2QFVIHO3FWZnm+vNtRevEz3EnJWoNC0f/SkoLNFMCdwIRm/RzmVUQ9TEAhL5HUcqJ5jO TnzzimPtsFqpS+9CKONRBk+jhb0+JX3trN5pPwLFNbvmQujTMsdo+6yjobpWBSXOriMt BPDqGP6e4tWWTFuCVoFAf+iL6LFP8C41rODQC44fBZsWfvl/ozsuJEd98rm3ihIVKQIL yRcw== X-Gm-Message-State: AOPr4FWSMuznsDDtbFUmRM8eqDugXkOm8phO/FsEh90IcNWdI6fvpJ0GPjfVPXjaVxrh0w== X-Received: by 10.66.236.167 with SMTP id uv7mr6469128pac.75.1462985160072; Wed, 11 May 2016 09:46:00 -0700 (PDT) Received: from wkstn-mjohnston.west.isilon.com (c-76-104-201-218.hsd1.wa.comcast.net. [76.104.201.218]) by smtp.gmail.com with ESMTPSA id qy8sm13452856pac.17.2016.05.11.09.45.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 11 May 2016 09:45:59 -0700 (PDT) Sender: Mark Johnston Date: Wed, 11 May 2016 09:49:45 -0700 From: Mark Johnston To: Abhishek Kulkarni Cc: "freebsd-dtrace@freebsd.org" Subject: Re: Regarding Dtrace on Arm Message-ID: <20160511164945.GB76917@wkstn-mjohnston.west.isilon.com> References: <85861491-5F47-4448-B933-E1394C578646@juniper.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <85861491-5F47-4448-B933-E1394C578646@juniper.net> User-Agent: Mutt/1.6.1 (2016-04-27) X-BeenThere: freebsd-dtrace@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: "A discussion list for developers working on DTrace in FreeBSD." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 11 May 2016 16:46:01 -0000 On Sat, May 07, 2016 at 08:55:56PM +0000, Abhishek Kulkarni wrote: > Hello All, > > I was using Dtrace using the FBT provider on an arm platform with witness enabled. When FBT is used with the kernel module, it generates a kernel panic or the system becomes unresponsive. Is this problem know or seen before. I am copying the kernel backtrace below for reference. The issue seems to be with a blockable sleep lock(kld_sx) acquired which is conflicting with the td->td_critnest positive value. Unfortunately, I think this is expected. The ARM port of DTrace will call into the kernel linker from probe context to perform stack unwinding. This is a bug since the kernel linker cannot be entered in arbitrary contexts - the thread might already hold the linker lock, or might hold a critical section as in your example. This is a known issue, but I'm not sure if anyone is working on fixing it. -Mark