On Wed, 14 Jan 2015 12:13:43 -0500
Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> wrote:
> On Wed, Jan 14, 2015 at 10:32 AM, Jeff Layton <jlayton@xxxxxxxxxxxxxxx> 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 [<ffffffff810ff58f>] 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:
> > [<ffffffff8186ac78>] dump_stack+0x4c/0x65
> > [<ffffffff810ac9da>] warn_slowpath_common+0x8a/0xc0
> > [<ffffffff810aca65>] warn_slowpath_fmt+0x55/0x70
> > [<ffffffff810ff58f>] ? prepare_to_wait+0x2f/0x90
> > [<ffffffff810ff58f>] ? prepare_to_wait+0x2f/0x90
> > [<ffffffff810dd2ad>] __might_sleep+0xbd/0xd0
> > [<ffffffff8124c973>] kmem_cache_alloc_trace+0x243/0x430
> > [<ffffffff810d941e>] ? groups_alloc+0x3e/0x130
> > [<ffffffff810d941e>] groups_alloc+0x3e/0x130
> > [<ffffffffa0301b1e>] svcauth_unix_accept+0x16e/0x290 [sunrpc]
> > [<ffffffffa0300571>] svc_authenticate+0xe1/0xf0 [sunrpc]
> > [<ffffffffa02fc564>] svc_process_common+0x244/0x6a0 [sunrpc]
> > [<ffffffffa02fd044>] bc_svc_process+0x1c4/0x260 [sunrpc]
> > [<ffffffffa03d5478>] nfs41_callback_svc+0x128/0x1f0 [nfsv4]
> > [<ffffffff810ff970>] ? wait_woken+0xc0/0xc0
> > [<ffffffffa03d5350>] ? nfs4_callback_svc+0x60/0x60 [nfsv4]
> > [<ffffffff810d45bf>] kthread+0x11f/0x140
> > [<ffffffff810ea815>] ? local_clock+0x15/0x30
> > [<ffffffff810d44a0>] ? kthread_create_on_node+0x250/0x250
> > [<ffffffff81874bfc>] ret_from_fork+0x7c/0xb0
> > [<ffffffff810d44a0>] ? 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.
>
> ACK.
>
> > Also, we don't expect this kthread to accept signals, so we should be
> > using a TASK_UNINTERRUPTIBLE sleep instead.
>
> Umm... Won't that end up triggering the hung task watchdog for every
> 120seconds with no callback activity?
>
Doh! You're correct.
What's the right way to do this then? Do we need to use
schedule_timeout and wake up every 100s or so? Using TASK_INTERRUPTIBLE
to work around the watchdog seems wrong but I guess we can live with
that in the short term if it's the only way.
Long-term, it would probably make sense to convert this (and other
service threads like this) over to workqueue-based services. I
still need to chase down where the latency comes from before that
patchset is ready for merge though.
> > Reported-by: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
> > ---
> > fs/nfs/callback.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
> > index b8fb3a4ef649..ebba958e084c 100644
> > --- a/fs/nfs/callback.c
> > +++ b/fs/nfs/callback.c
> > @@ -128,13 +128,14 @@ 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", @@ -142,8 +143,8 @@ nfs41_callback_svc(void *vrqstp)
> > } else {
> > spin_unlock_bh(&serv->sv_cb_lock);
> > schedule();
> > + finish_wait(&serv->sv_cb_waitq, &wq);
> > }
> > - finish_wait(&serv->sv_cb_waitq, &wq);
> > }
> > return 0;
> > }
> > --
> > 2.1.0
> >
>
>
>
--
Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
