Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263365AbTIWNlh (ORCPT ); Tue, 23 Sep 2003 09:41:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263371AbTIWNlg (ORCPT ); Tue, 23 Sep 2003 09:41:36 -0400 Received: from mail-01.iinet.net.au ([203.59.3.33]:45024 "HELO mail.iinet.net.au") by vger.kernel.org with SMTP id S263365AbTIWNl1 (ORCPT ); Tue, 23 Sep 2003 09:41:27 -0400 Date: Tue, 23 Sep 2003 21:47:23 +0800 (WST) From: Ian Kent To: Kernel Mailing List cc: Maneesh Soni , Jeremy Fitzhardinge Subject: [PATCH] autofs4 deadlock during expire - kernel 2.6 Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2596 Lines: 70 I have noticed that a deadlock can occur in the autofs4 module in the 2.6 kernel and RedHat kernels with the O(1) scheduler patch. The easiest way to reproduce it is with an autofs-4.0.0 tree mount with at least 10 mounts within a Nautilus desktop environment with the module debug flag set. Perhaps this is because of the longish amount of time spent in the expire state. The scenario: 1) An expire locates an expirable dentry and signals the user space daemon to umount it. 2) During the umount operation Nautilus notices and scans entries in the directory tree triggering a revalidate/lookup. 3) autofs4 places the requesting process on the umount wait queue. 4) At completion of the expire both process are released from the wait queue. 5) If the lookup gets a quantum first deadlock occurs and expiration stops leaving an autofs mount that is permanently busy. The following patch fixes this by ensuring that the expire gets a lookin before the revalidate/lookup continues. The problem of the remount that this causes remains and I an not sure how to deal with that at this stage. Comments and suggestions please. Is this acceptable for inclusion in the kernel? If so what should I do to make this happen? diff -Nur autofs4-2.6.orig/fs/autofs4/autofs_i.h autofs4-2.6.deadlock/fs/autofs4/autofs_i.h --- autofs4-2.6.orig/fs/autofs4/autofs_i.h 2003-09-09 03:50:14.000000000 +0800 +++ autofs4-2.6.deadlock/fs/autofs4/autofs_i.h 2003-09-22 22:48:11.000000000 +0800 @@ -82,6 +82,7 @@ char *name; /* This is for status reporting upon return */ int status; + struct task_struct *owner; int wait_ctr; }; diff -Nur autofs4-2.6.orig/fs/autofs4/waitq.c autofs4-2.6.deadlock/fs/autofs4/waitq.c --- autofs4-2.6.orig/fs/autofs4/waitq.c 2003-09-09 03:50:31.000000000 +0800 +++ autofs4-2.6.deadlock/fs/autofs4/waitq.c 2003-09-23 00:02:29.209789432 +0800 @@ -206,6 +206,11 @@ interruptible_sleep_on(&wq->queue); + if (waitqueue_active(&wq->queue) && current != wq->owner) { + set_current_state(TASK_INTERRUPTIBLE); + schedule_timeout(wq->wait_ctr * (HZ/10)); + } + spin_lock_irqsave(¤t->sighand->siglock, irqflags); current->blocked = oldset; recalc_sigpending(); -- ,-._|\ Ian Kent / \ Perth, Western Australia *_.--._/ E-mail: raven@themaw.net v Web: http://themaw.net/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/