From owner-freebsd-bugs@FreeBSD.ORG Fri Nov 21 16:40:02 2008 Return-Path: Delivered-To: freebsd-bugs@hub.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C670B106567A for ; Fri, 21 Nov 2008 16:40:02 +0000 (UTC) (envelope-from gnats@FreeBSD.org) Received: from freefall.freebsd.org (freefall.freebsd.org [IPv6:2001:4f8:fff6::28]) by mx1.freebsd.org (Postfix) with ESMTP id A71F48FC25 for ; Fri, 21 Nov 2008 16:40:02 +0000 (UTC) (envelope-from gnats@FreeBSD.org) Received: from freefall.freebsd.org (gnats@localhost [127.0.0.1]) by freefall.freebsd.org (8.14.3/8.14.3) with ESMTP id mALGe2BY096022 for ; Fri, 21 Nov 2008 16:40:02 GMT (envelope-from gnats@freefall.freebsd.org) Received: (from gnats@localhost) by freefall.freebsd.org (8.14.3/8.14.3/Submit) id mALGe2HF096021; Fri, 21 Nov 2008 16:40:02 GMT (envelope-from gnats) Resent-Date: Fri, 21 Nov 2008 16:40:02 GMT Resent-Message-Id: <200811211640.mALGe2HF096021@freefall.freebsd.org> Resent-From: FreeBSD-gnats-submit@FreeBSD.org (GNATS Filer) Resent-To: freebsd-bugs@FreeBSD.org Resent-Reply-To: FreeBSD-gnats-submit@FreeBSD.org, Brad Huntting Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 506AC106564A for ; Fri, 21 Nov 2008 16:37:01 +0000 (UTC) (envelope-from nobody@FreeBSD.org) Received: from www.freebsd.org (www.freebsd.org [IPv6:2001:4f8:fff6::21]) by mx1.freebsd.org (Postfix) with ESMTP id 43C778FC08 for ; Fri, 21 Nov 2008 16:37:01 +0000 (UTC) (envelope-from nobody@FreeBSD.org) Received: from www.freebsd.org (localhost [127.0.0.1]) by www.freebsd.org (8.14.3/8.14.3) with ESMTP id mALGb05L094873 for ; Fri, 21 Nov 2008 16:37:00 GMT (envelope-from nobody@www.freebsd.org) Received: (from nobody@localhost) by www.freebsd.org (8.14.3/8.14.3/Submit) id mALGb0GK094872; Fri, 21 Nov 2008 16:37:00 GMT (envelope-from nobody) Message-Id: <200811211637.mALGb0GK094872@www.freebsd.org> Date: Fri, 21 Nov 2008 16:37:00 GMT From: Brad Huntting To: freebsd-gnats-submit@FreeBSD.org X-Send-Pr-Version: www-3.1 Cc: Subject: kern/129053: lock order reversal X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 21 Nov 2008 16:40:02 -0000 >Number: 129053 >Category: kern >Synopsis: lock order reversal >Confidential: no >Severity: serious >Priority: medium >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Fri Nov 21 16:40:02 UTC 2008 >Closed-Date: >Last-Modified: >Originator: Brad Huntting >Release: 7.1-PRERELEASE >Organization: >Environment: FreeBSD spork.glarp.com 7.1-PRERELEASE FreeBSD 7.1-PRERELEASE #4: Thu Nov 13 11:34:12 MST 2008 root@spork.glarp.com:/usr/src/sys/i386/compile/SPORK i386 >Description: My device driver (a proprietary USB device called 'scmicro') appears to have tickled a lock order reversal. When witness.watch is enabled, all goes well until my driver detach()es. At which point my system panics with: lock order reversal: 1st 0xc0c932a0 syscons video lock (syscons video lock) @ dev/syscons/syscons.c:2534 2nd 0xc0c23400 sched lock 0 (sched lock) @ kern/kern_clock.c:286 panic: blockable sleep lock (sleep mutex) sellck @ kern/sys_generic.c:1127 My driver creates two taskqueue(9) threads in attach() and destroys them in detach(). It has 4 mutexes which it uses to protect it's own data structures. In addition, it holds Giant around any code section which calls usb functions. With the exception of wakeup(9), cv_signal(9), cv_destroy(9) and taskqueue_enqueue_fast(), it always release it's own locks (except for Giant) before it calls external code. Of course, this does not happen when my devices uses the ugen(4) driver. Is this a known issue? Am I doing something wrong? >How-To-Repeat: Sorry, my client wont let me release details of the driver. >Fix: >Release-Note: >Audit-Trail: >Unformatted: