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Date: Wed, 29 Mar 2017 12:53:28 +0100 From: John Garry <john.garry@...wei.com> To: Johannes Thumshirn <jthumshirn@...e.de> CC: "Martin K . Petersen" <martin.petersen@...cle.com>, Tejun Heo <tj@...nel.org>, James Bottomley <jejb@...ux.vnet.ibm.com>, Dan Williams <dan.j.williams@...el.com>, Jack Wang <jinpu.wang@...fitbricks.com>, "Hannes Reinecke" <hare@...e.de>, Linux SCSI Mailinglist <linux-scsi@...r.kernel.org>, Linux Kernel Mailinglist <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 1/2] scsi: sas: flush destruct workqueue on device unregister On 29/03/2017 12:29, Johannes Thumshirn wrote: > On Wed, Mar 29, 2017 at 12:15:44PM +0100, John Garry wrote: >> On 29/03/2017 10:41, Johannes Thumshirn wrote: >>> In the advent of an SAS device unregister we have to wait for all destruct >>> works to be done to not accidently delay deletion of a SAS rphy or it's >>> children to the point when we're removing the SCSI or SAS hosts. >>> >>> Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de> >>> --- >>> drivers/scsi/libsas/sas_discover.c | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/drivers/scsi/libsas/sas_discover.c b/drivers/scsi/libsas/sas_discover.c >>> index 60de662..75b18f1 100644 >>> --- a/drivers/scsi/libsas/sas_discover.c >>> +++ b/drivers/scsi/libsas/sas_discover.c >>> @@ -382,9 +382,13 @@ void sas_unregister_dev(struct asd_sas_port *port, struct domain_device *dev) >>> } >>> >>> if (!test_and_set_bit(SAS_DEV_DESTROY, &dev->state)) { >>> + struct sas_discovery *disc = &dev->port->disc; >>> + struct sas_work *sw = &disc->disc_work[DISCE_DESTRUCT].work; >>> + >>> sas_rphy_unlink(dev->rphy); >>> list_move_tail(&dev->disco_list_node, &port->destroy_list); >>> sas_discover_event(dev->port, DISCE_DESTRUCT); >>> + flush_work(&sw->work); >> >> I quickly tested plugging out the expander and we never get past this call >> to flush - a hang results: > > Can you activat lockdep so we can see which lock it is that we're blocking on? > I have it on: CONFIG_LOCKDEP_SUPPORT=y CONFIG_LOCKD=y CONFIG_LOCKD_V4=y > It's most likely in sas_unregister_common_dev() but this function takes two spin > locks, port->dev_list_lock and ha->lock. > We can see from the callstack I provided that we're working in workqueue scsi_wq_0 and trying to flush that same queue. Much appreciated, John > Thanks a lot, > Johannes >
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