| Message ID | 11AF7C027C4C02408624617A4986078401323542@BPXM12GP.gisp.nec.co.jp (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On 07/08/2014 08:28 PM, Junichi Nomura wrote: > On 07/02/14 04:39, Mike Snitzer wrote: >> On Mon, Jun 30 2014 at 6:30am -0400, >> Paul Mackerras <paulus@samba.org> wrote: >> >>> I have a machine on which 3.15 usually fails to boot, and 3.14 boots >>> every time. The machine is a POWER8 2-socket server with 20 cores >>> (thus 160 CPUs), 128GB of RAM, and 7 SCSI disks connected via a >>> hardware-RAID-capable adapter which appears as two IPR controllers >>> which are both connected to each disk. I am booting from a disk that >>> has Fedora 20 installed on it. >>> >>> After over two weeks of bisections, I can finally point to the commits >>> that cause the problems. The culprits are: >>> >>> 3e9f1be1 dm mpath: remove process_queued_ios() >>> e8099177 dm mpath: push back requests instead of queueing >>> bcccff93 kobject: don't block for each kobject_uevent >>> >>> The interesting thing is that neither e8099177 nor bcccff93 cause >>> failures on their own, but with both commits in there are failures >>> where the system will fail to find /home on some occasions. >>> >>> With 3e9f1be1 included, the system appears to be prone to a deadlock >>> condition which typically causes the boot process to hang with this >>> message showing: >>> >>> A start job is running for Monitoring of LVM2 mirror...rogress polling >>> >>> (with a [*** ] thing before it where the asterisks move back and >>> forth). >>> >>> If I revert 63d832c3 ("dm mpath: really fix lockdep warning") , >>> 4cdd2ad7 ("dm mpath: fix lock order inconsistency in >>> multipath_ioctl"), 3e9f1be1 and bcccff93, in that order, I get a >>> kernel that will boot every time. The first two are later commits >>> that fix some problems with 3e9f1be1 (though not the problems I am >>> seeing). >>> >>> Can anyone see any reason why e8099177 and bcccff93 would interfere >>> with each other? >> >> No, not seeing any obvious relation. >> >> But even though you listed e8099177 as a culprit you didn't list it as a >> commit you reverted. Did you leave e8099177 simply because attempting >> to revert it fails (if you don't first revert other dm-mpath.c commits)? >> >> (btw, Bart Van Assche also has issues with commit e8099177 due to hangs >> during cable pull testing of mpath devices -- Bart: curious to know if >> your cable pull tests pass if you just revert bcccff93). > > It seems Bart's issue has gone with the attached patch: > http://www.redhat.com/archives/dm-devel/2014-July/msg00035.html > Could you try if it makes any difference on your issue? > > The problem is dm-mpath's state machine stall due to e8099177 > but ioctl to the device can kick the state machine running again. > That might be related to why bcccff93 affects the reproducibility. > Also, 3e9f1be1 integrates some codes into the one which is affected > by this problem. So it makes sense why the problem becomes easier > to occur with that. > > - > Jun'ichi Nomura, NEC Corporation > > > pg_ready() checks the current state of the multipath and may return > false even if a new IO is needed to change the state. > > OTOH, if multipath_busy() returns busy, a new IO will not be sent > to multipath target and the state change won't happen. That results > in lock up. > > The intent of multipath_busy() is to avoid unnecessary cycles of > dequeue + request_fn + requeue if it is known that multipath device > will requeue. > > Such situation would be: > - path group is being activated > - there is no path and the multipath is setup to requeue if no path > > This patch should fix the problem introduced as a part of this commit: > commit e809917735ebf1b9a56c24e877ce0d320baee2ec > dm mpath: push back requests instead of queueing > > diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c > index ebfa411..d58343e 100644 > --- a/drivers/md/dm-mpath.c > +++ b/drivers/md/dm-mpath.c > @@ -1620,8 +1620,9 @@ static int multipath_busy(struct dm_target *ti) > > spin_lock_irqsave(&m->lock, flags); > > - /* pg_init in progress, requeue until done */ > - if (!pg_ready(m)) { > + /* pg_init in progress or no paths available */ > + if (m->pg_init_in_progress || > + (!m->nr_valid_paths && m->queue_if_no_path)) { > busy = 1; > goto out; > } This patch fixes IPR SCSI for my POWER8 box, e8099177 was the problem.
On 07/09/14 12:55, Alexey Kardashevskiy wrote: > On 07/08/2014 08:28 PM, Junichi Nomura wrote: >> It seems Bart's issue has gone with the attached patch: >> http://www.redhat.com/archives/dm-devel/2014-July/msg00035.html >> Could you try if it makes any difference on your issue? .. > This patch fixes IPR SCSI for my POWER8 box, e8099177 was the problem. Thank you for the testing. Mike Snitzer has picked up this patch for his tree: https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=75c76c45b76e53b7c2f025d30e7e308bfe331004
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index ebfa411..d58343e 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -1620,8 +1620,9 @@ static int multipath_busy(struct dm_target *ti) spin_lock_irqsave(&m->lock, flags); - /* pg_init in progress, requeue until done */ - if (!pg_ready(m)) { + /* pg_init in progress or no paths available */ + if (m->pg_init_in_progress || + (!m->nr_valid_paths && m->queue_if_no_path)) { busy = 1; goto out; }