Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:58272 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751241AbbANTFH (ORCPT ); Wed, 14 Jan 2015 14:05:07 -0500 Date: Wed, 14 Jan 2015 14:05:06 -0500 From: "J. Bruce Fields" To: Jeff Layton Cc: trond.myklebust@primarydata.com, linux-nfs@vger.kernel.org Subject: Re: [PATCH v2] nfs: don't call blocking operations while !TASK_RUNNING Message-ID: <20150114190506.GB5069@fieldses.org> References: <1421249572-12038-1-git-send-email-jlayton@primarydata.com> <1421258937-18613-1-git-send-email-jlayton@primarydata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1421258937-18613-1-git-send-email-jlayton@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Wed, Jan 14, 2015 at 01:08:57PM -0500, Jeff Layton wrote: > Bruce reported seeing this warning pop when mounting using v4.1: > > ------------[ cut here ]------------ > WARNING: CPU: 1 PID: 1121 at kernel/sched/core.c:7300 __might_sleep+0xbd/0xd0() > do not call blocking ops when !TASK_RUNNING; state=1 set at [] prepare_to_wait+0x2f/0x90 > Modules linked in: rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs lockd grace sunrpc fscache ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw snd_hda_codec_generic snd_hda_intel snd_hda_controller snd_hda_codec snd_hwdep snd_pcm snd_timer ppdev joydev snd virtio_console virtio_balloon pcspkr serio_raw parport_pc parport pvpanic floppy soundcore i2c_piix4 virtio_blk virtio_net qxl drm_kms_helper ttm drm virtio_pci virtio_ring ata_generic virtio pata_acpi > CPU: 1 PID: 1121 Comm: nfsv4.1-svc Not tainted 3.19.0-rc4+ #25 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140709_153950- 04/01/2014 > 0000000000000000 000000004e5e3f73 ffff8800b998fb48 ffffffff8186ac78 > 0000000000000000 ffff8800b998fba0 ffff8800b998fb88 ffffffff810ac9da > ffff8800b998fb68 ffffffff81c923e7 00000000000004d9 0000000000000000 > Call Trace: > [] dump_stack+0x4c/0x65 > [] warn_slowpath_common+0x8a/0xc0 > [] warn_slowpath_fmt+0x55/0x70 > [] ? prepare_to_wait+0x2f/0x90 > [] ? prepare_to_wait+0x2f/0x90 > [] __might_sleep+0xbd/0xd0 > [] kmem_cache_alloc_trace+0x243/0x430 > [] ? groups_alloc+0x3e/0x130 > [] groups_alloc+0x3e/0x130 > [] svcauth_unix_accept+0x16e/0x290 [sunrpc] > [] svc_authenticate+0xe1/0xf0 [sunrpc] > [] svc_process_common+0x244/0x6a0 [sunrpc] > [] bc_svc_process+0x1c4/0x260 [sunrpc] > [] nfs41_callback_svc+0x128/0x1f0 [nfsv4] > [] ? wait_woken+0xc0/0xc0 > [] ? nfs4_callback_svc+0x60/0x60 [nfsv4] > [] kthread+0x11f/0x140 > [] ? local_clock+0x15/0x30 > [] ? kthread_create_on_node+0x250/0x250 > [] ret_from_fork+0x7c/0xb0 > [] ? kthread_create_on_node+0x250/0x250 > ---[ end trace 675220a11e30f4f2 ]--- > > nfs41_callback_svc does most of its work while in TASK_INTERRUPTIBLE, > which is just wrong. Fix that by finishing the wait immediately if we've > found that the list has something on it. > > Also, we don't expect this kthread to accept signals, so we should be > using a TASK_UNINTERRUPTIBLE sleep instead. That however, opens us up > hung task warnings from the watchdog, so have the schedule_timeout > wake up every 60s if there's no callback activity. Works for me, for what it's worth. > > Reported-by: "J. Bruce Fields" > Signed-off-by: Jeff Layton > --- > fs/nfs/callback.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c > index b8fb3a4ef649..351be9205bf8 100644 > --- a/fs/nfs/callback.c > +++ b/fs/nfs/callback.c > @@ -128,22 +128,24 @@ nfs41_callback_svc(void *vrqstp) > if (try_to_freeze()) > continue; > > - prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_INTERRUPTIBLE); > + prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_UNINTERRUPTIBLE); > spin_lock_bh(&serv->sv_cb_lock); > if (!list_empty(&serv->sv_cb_list)) { > req = list_first_entry(&serv->sv_cb_list, > struct rpc_rqst, rq_bc_list); > list_del(&req->rq_bc_list); > spin_unlock_bh(&serv->sv_cb_lock); > + finish_wait(&serv->sv_cb_waitq, &wq); > dprintk("Invoking bc_svc_process()\n"); > error = bc_svc_process(serv, req, rqstp); > dprintk("bc_svc_process() returned w/ error code= %d\n", > error); > } else { > spin_unlock_bh(&serv->sv_cb_lock); > - schedule(); > + /* schedule_timeout to game the hung task watchdog */ > + schedule_timeout(60 * HZ); > + finish_wait(&serv->sv_cb_waitq, &wq); > } > - finish_wait(&serv->sv_cb_waitq, &wq); > } > return 0; > } > -- > 2.1.0 >