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authorJames Smart <James.Smart@Emulex.Com>2006-04-10 10:14:05 -0400
committerJames Bottomley <jejb@mulgrave.il.steeleye.com>2006-04-13 13:25:16 -0500
commitaedf349773e5877d716a89368d512b9baa3e8c7b (patch)
treeacc08d181b97c434c70c7ad984e262813067ba89 /include/scsi
parentb0d2364887e94c880680f1e17943cd660bcf8979 (diff)
[SCSI] FC transport: fixes for workq deadlocks
As previously reported via Michael Reed, the FC transport took a hit in 2.6.15 (perhaps a little earlier) when we solved a recursion error. There are 2 deadlocks occurring: - With scan and the delete items sharing the same workq, flushing the workq for the delete code was getting it stalled behind a very long running scan code path. - There's a deadlock where scsi_remove_target() has to sit behind scsi_scan_target() due to contention over the scan_lock(). This patch resolves the 1st deadlock and significantly reduces the odds of the second. So far, we have only replicated the 2nd deadlock on a highly-parallel SMP system. More on the 2nd deadlock in a following email. This patch reworks the transport to: - Only use the scsi host workq for scanning - Use 2 other workq's internally. One for deletions, the other for scheduled deletions. Originally, we tried this with a single workq, but the occassional flushes of the scheduled queues was hitting the second deadlock with a slightly higher frequency. In the future, we'll look at the LLDD's and the transport to see if we can get rid of this extra overhead. - When moving to the other workq's we tightened up some object states and some lock handling. - Properly syncs adds/deletes - minor code cleanups - directly reference fc_host_attrs, rather than through attribute macros - flush the right workq on delayed work cancel failures. Large kudos to Michael Reed who has been working this issue for the last month. Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
Diffstat (limited to 'include/scsi')
-rw-r--r--include/scsi/scsi_transport_fc.h41
1 files changed, 30 insertions, 11 deletions
diff --git a/include/scsi/scsi_transport_fc.h b/include/scsi/scsi_transport_fc.h
index cf3fec8be1e..5626225bd3a 100644
--- a/include/scsi/scsi_transport_fc.h
+++ b/include/scsi/scsi_transport_fc.h
@@ -202,12 +202,19 @@ struct fc_rport { /* aka fc_starget_attrs */
/* internal data */
unsigned int channel;
u32 number;
+ u8 flags;
struct list_head peers;
struct device dev;
struct work_struct dev_loss_work;
struct work_struct scan_work;
+ struct work_struct stgt_delete_work;
+ struct work_struct rport_delete_work;
} __attribute__((aligned(sizeof(unsigned long))));
+/* bit field values for struct fc_rport "flags" field: */
+#define FC_RPORT_DEVLOSS_PENDING 0x01
+#define FC_RPORT_SCAN_PENDING 0x02
+
#define dev_to_rport(d) \
container_of(d, struct fc_rport, dev)
#define transport_class_to_rport(classdev) \
@@ -327,13 +334,16 @@ struct fc_host_attrs {
struct list_head rport_bindings;
u32 next_rport_number;
u32 next_target_id;
- u8 flags;
- struct work_struct rport_del_work;
-};
-/* values for struct fc_host_attrs "flags" field: */
-#define FC_SHOST_RPORT_DEL_SCHEDULED 0x01
+ /* work queues for rport state manipulation */
+ char work_q_name[KOBJ_NAME_LEN];
+ struct workqueue_struct *work_q;
+ char devloss_work_q_name[KOBJ_NAME_LEN];
+ struct workqueue_struct *devloss_work_q;
+};
+#define shost_to_fc_host(x) \
+ ((struct fc_host_attrs *)(x)->shost_data)
#define fc_host_node_name(x) \
(((struct fc_host_attrs *)(x)->shost_data)->node_name)
@@ -375,10 +385,14 @@ struct fc_host_attrs {
(((struct fc_host_attrs *)(x)->shost_data)->next_rport_number)
#define fc_host_next_target_id(x) \
(((struct fc_host_attrs *)(x)->shost_data)->next_target_id)
-#define fc_host_flags(x) \
- (((struct fc_host_attrs *)(x)->shost_data)->flags)
-#define fc_host_rport_del_work(x) \
- (((struct fc_host_attrs *)(x)->shost_data)->rport_del_work)
+#define fc_host_work_q_name(x) \
+ (((struct fc_host_attrs *)(x)->shost_data)->work_q_name)
+#define fc_host_work_q(x) \
+ (((struct fc_host_attrs *)(x)->shost_data)->work_q)
+#define fc_host_devloss_work_q_name(x) \
+ (((struct fc_host_attrs *)(x)->shost_data)->devloss_work_q_name)
+#define fc_host_devloss_work_q(x) \
+ (((struct fc_host_attrs *)(x)->shost_data)->devloss_work_q)
/* The functions by which the transport class and the driver communicate */
@@ -461,10 +475,15 @@ fc_remote_port_chkready(struct fc_rport *rport)
switch (rport->port_state) {
case FC_PORTSTATE_ONLINE:
- result = 0;
+ if (rport->roles & FC_RPORT_ROLE_FCP_TARGET)
+ result = 0;
+ else if (rport->flags & FC_RPORT_DEVLOSS_PENDING)
+ result = DID_IMM_RETRY << 16;
+ else
+ result = DID_NO_CONNECT << 16;
break;
case FC_PORTSTATE_BLOCKED:
- result = DID_BUS_BUSY << 16;
+ result = DID_IMM_RETRY << 16;
break;
default:
result = DID_NO_CONNECT << 16;