From owner-freebsd-virtualization@freebsd.org Fri Nov 8 21:44:03 2019 Return-Path: Delivered-To: freebsd-virtualization@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 55B791614DF for ; Fri, 8 Nov 2019 21:44:03 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mailman.nyi.freebsd.org (unknown [127.0.1.3]) by mx1.freebsd.org (Postfix) with ESMTP id 478v0z1Zvyz3yBq for ; Fri, 8 Nov 2019 21:44:03 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.nyi.freebsd.org (Postfix) id 364701614DE; Fri, 8 Nov 2019 21:44:03 +0000 (UTC) Delivered-To: virtualization@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 360831614DD for ; Fri, 8 Nov 2019 21:44:03 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 478v0z0j6mz3yBm for ; Fri, 8 Nov 2019 21:44:03 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2610:1c1:1:606c::50:1d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id EF70349B4 for ; Fri, 8 Nov 2019 21:44:02 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.5]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id xA8Li2Ah051731 for ; Fri, 8 Nov 2019 21:44:02 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id xA8Li2xn051730 for virtualization@FreeBSD.org; Fri, 8 Nov 2019 21:44:02 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: virtualization@FreeBSD.org Subject: [Bug 241808] bhyve e1000 broken after r354288 Date: Fri, 08 Nov 2019 21:44:03 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: bhyve X-Bugzilla-Version: CURRENT X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Many People X-Bugzilla-Who: vmaffione@FreeBSD.org X-Bugzilla-Status: In Progress X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: virtualization@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_status Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-virtualization@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Discussion of various virtualization techniques FreeBSD supports." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 08 Nov 2019 21:44:03 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D241808 Vincenzo Maffione changed: What |Removed |Added ---------------------------------------------------------------------------- Status|New |In Progress --- Comment #1 from Vincenzo Maffione --- Very interesting, thanks for catching it. I think the real problem here (even before r354288) is that nothing prevent= s a call to kevent(fd, EV_ENABLE) to happen before kevent(fd, EVADD) is called,= as you are reporting. On mevent_add() and mevent_update(), mevent_notify() is called to wakeup the I/O thread, that will call kevent(changelist) to update the kernel. A race condition is possible where the client calls mevent_add() and mevent_update(EV_ENABLE) before the I/O thread has the chance to wake up and calls mevent_build()+kevent(changelist), which is exactly what happens in y= our case. r354288 only makes this race condition more likely (this explains why I did= not catch the bug on my machine when I tested e1000). Your fix makes the race condition less likely, but I think it's still there. I tried to rework and simplify mevent.c to make sure EV_ADD is always called before EV_ENABLE or EV_DISABLE. Let me know what you think about that: https://reviews.freebsd.org/D22286 --=20 You are receiving this mail because: You are the assignee for the bug.=