Skip to content

Commit

Permalink
[SCSI] zfcp: Fix deadlock between zfcp ERP and SCSI
Browse files Browse the repository at this point in the history
The SCSI stack requires low level drivers to register and
unregister devices. For zfcp this leads to the situation where
zfcp calls the SCSI stack, the SCSI tries to scan the new device
and the scan SCSI command fails. This would require the zfcp erp,
but the erp thread is already blocked in the register call.

The fix is to make sure that the calls from the ERP thread to
the SCSI stack do not block the ERP thread. In detail:
1) Use a workqueue to avoid blocking of the scsi_scan_target calls.
2) When removing a unit make sure that no scsi_scan_target call is
   pending.
3) Replace scsi_flush_work with scsi_target_unblock. This avoids
   blocking and has the same result.

Signed-off-by: Christof Schmitt <[email protected]>
Signed-off-by: Swen Schillig <[email protected]>
Signed-off-by: James Bottomley <[email protected]>
  • Loading branch information
Christof Schmitt authored and James Bottomley committed May 8, 2007
1 parent 801e0ce commit 5f852be
Show file tree
Hide file tree
Showing 4 changed files with 72 additions and 4 deletions.
2 changes: 2 additions & 0 deletions drivers/s390/scsi/zfcp_aux.c
Original file line number Diff line number Diff line change
Expand Up @@ -913,6 +913,8 @@ zfcp_unit_enqueue(struct zfcp_port *port, fcp_lun_t fcp_lun)
unit->sysfs_device.release = zfcp_sysfs_unit_release;
dev_set_drvdata(&unit->sysfs_device, unit);

init_waitqueue_head(&unit->scsi_scan_wq);

/* mark unit unusable as long as sysfs registration is not complete */
atomic_set_mask(ZFCP_STATUS_COMMON_REMOVE, &unit->status);

Expand Down
5 changes: 5 additions & 0 deletions drivers/s390/scsi/zfcp_def.h
Original file line number Diff line number Diff line change
Expand Up @@ -637,6 +637,7 @@ do { \
#define ZFCP_STATUS_UNIT_SHARED 0x00000004
#define ZFCP_STATUS_UNIT_READONLY 0x00000008
#define ZFCP_STATUS_UNIT_REGISTERED 0x00000010
#define ZFCP_STATUS_UNIT_SCSI_WORK_PENDING 0x00000020

/* FSF request status (this does not have a common part) */
#define ZFCP_STATUS_FSFREQ_NOT_INIT 0x00000000
Expand Down Expand Up @@ -980,6 +981,10 @@ struct zfcp_unit {
struct scsi_device *device; /* scsi device struct pointer */
struct zfcp_erp_action erp_action; /* pending error recovery */
atomic_t erp_counter;
wait_queue_head_t scsi_scan_wq; /* can be used to wait until
all scsi_scan_target
requests have been
completed. */
};

/* FSF request */
Expand Down
64 changes: 60 additions & 4 deletions drivers/s390/scsi/zfcp_erp.c
Original file line number Diff line number Diff line change
Expand Up @@ -1591,6 +1591,62 @@ zfcp_erp_strategy_check_adapter(struct zfcp_adapter *adapter, int result)
return result;
}

struct zfcp_erp_add_work {
struct zfcp_unit *unit;
struct work_struct work;
};

/**
* zfcp_erp_scsi_scan
* @data: pointer to a struct zfcp_erp_add_work
*
* Registers a logical unit with the SCSI stack.
*/
static void zfcp_erp_scsi_scan(struct work_struct *work)
{
struct zfcp_erp_add_work *p =
container_of(work, struct zfcp_erp_add_work, work);
struct zfcp_unit *unit = p->unit;
struct fc_rport *rport = unit->port->rport;
scsi_scan_target(&rport->dev, 0, rport->scsi_target_id,
unit->scsi_lun, 0);
atomic_clear_mask(ZFCP_STATUS_UNIT_SCSI_WORK_PENDING, &unit->status);
wake_up(&unit->scsi_scan_wq);
zfcp_unit_put(unit);
kfree(p);
}

/**
* zfcp_erp_schedule_work
* @unit: pointer to unit which should be registered with SCSI stack
*
* Schedules work which registers a unit with the SCSI stack
*/
static void
zfcp_erp_schedule_work(struct zfcp_unit *unit)
{
struct zfcp_erp_add_work *p;

p = kmalloc(sizeof(*p), GFP_KERNEL);
if (!p) {
ZFCP_LOG_NORMAL("error: Out of resources. Could not register "
"the FCP-LUN 0x%Lx connected to "
"the port with WWPN 0x%Lx connected to "
"the adapter %s with the SCSI stack.\n",
unit->fcp_lun,
unit->port->wwpn,
zfcp_get_busid_by_unit(unit));
return;
}

zfcp_unit_get(unit);
memset(p, 0, sizeof(*p));
atomic_set_mask(ZFCP_STATUS_UNIT_SCSI_WORK_PENDING, &unit->status);
INIT_WORK(&p->work, zfcp_erp_scsi_scan);
p->unit = unit;
schedule_work(&p->work);
}

/*
* function:
*
Expand Down Expand Up @@ -3092,9 +3148,9 @@ zfcp_erp_action_cleanup(int action, struct zfcp_adapter *adapter,
&& port->rport) {
atomic_set_mask(ZFCP_STATUS_UNIT_REGISTERED,
&unit->status);
scsi_scan_target(&port->rport->dev, 0,
port->rport->scsi_target_id,
unit->scsi_lun, 0);
if (atomic_test_mask(ZFCP_STATUS_UNIT_SCSI_WORK_PENDING,
&unit->status) == 0)
zfcp_erp_schedule_work(unit);
}
zfcp_unit_put(unit);
break;
Expand All @@ -3121,7 +3177,7 @@ zfcp_erp_action_cleanup(int action, struct zfcp_adapter *adapter,
zfcp_get_busid_by_port(port),
port->wwpn);
else {
scsi_flush_work(adapter->scsi_host);
scsi_target_unblock(&port->rport->dev);
port->rport->maxframe_size = port->maxframe_size;
port->rport->supported_classes =
port->supported_classes;
Expand Down
5 changes: 5 additions & 0 deletions drivers/s390/scsi/zfcp_scsi.c
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@
#define ZFCP_LOG_AREA ZFCP_LOG_AREA_SCSI

#include "zfcp_ext.h"
#include <asm/atomic.h>

static void zfcp_scsi_slave_destroy(struct scsi_device *sdp);
static int zfcp_scsi_slave_alloc(struct scsi_device *sdp);
Expand Down Expand Up @@ -179,6 +180,10 @@ static void zfcp_scsi_slave_destroy(struct scsi_device *sdpnt)
struct zfcp_unit *unit = (struct zfcp_unit *) sdpnt->hostdata;

if (unit) {
zfcp_erp_wait(unit->port->adapter);
wait_event(unit->scsi_scan_wq,
atomic_test_mask(ZFCP_STATUS_UNIT_SCSI_WORK_PENDING,
&unit->status) == 0);
atomic_clear_mask(ZFCP_STATUS_UNIT_REGISTERED, &unit->status);
sdpnt->hostdata = NULL;
unit->device = NULL;
Expand Down

0 comments on commit 5f852be

Please sign in to comment.