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4da8c5f768
Case (1):
The only waiter on wka_port->completion_wq is zfcp_fc_wka_port_get()
trying to open a WKA port. As such it should only be woken up by WKA port
*open* responses, not by WKA port close responses.
Case (2):
A close WKA port response coming in just after having sent a new open WKA
port request and before blocking for the open response with wait_event()
in zfcp_fc_wka_port_get() erroneously renders the wait_event a NOP
because the close handler overwrites wka_port->status. Hence the
wait_event condition is erroneously true and it does not enter blocking
state.
With non-negligible probability, the following time space sequence happens
depending on timing without this fix:
user process ERP thread zfcp work queue tasklet system work queue
============ ========== =============== ======= =================
$ echo 1 > online
zfcp_ccw_set_online
zfcp_ccw_activate
zfcp_erp_adapter_reopen
msleep scan backoff zfcp_erp_strategy
| ...
| zfcp_erp_action_cleanup
| ...
| queue delayed scan_work
| queue ns_up_work
| ns_up_work:
| zfcp_fc_wka_port_get
| open wka request
| open response
| GSPN FC-GS
| RSPN FC-GS [NPIV-only]
| zfcp_fc_wka_port_put
| (--wka->refcount==0)
| sched delayed wka->work
|
~~~Case (1)~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
zfcp_erp_wait
flush scan_work
| wka->work:
| wka->status=CLOSING
| close wka request
| scan_work:
| zfcp_fc_wka_port_get
| (wka->status==CLOSING)
| wka->status=OPENING
| open wka request
| wait_event
| | close response
| | wka->status=OFFLINE
| | wake_up /*WRONG*/
~~~Case (2)~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| wka->work:
| wka->status=CLOSING
| close wka request
zfcp_erp_wait
flush scan_work
| scan_work:
| zfcp_fc_wka_port_get
| (wka->status==CLOSING)
| wka->status=OPENING
| open wka request
| close response
| wka->status=OFFLINE
| wake_up /*WRONG&NOP*/
| wait_event /*NOP*/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| (wka->status!=ONLINE)
| return -EIO
| return early
open response
wka->status=ONLINE
wake_up /*NOP*/
So we erroneously end up with no automatic port scan. This is a big problem
when it happens during boot. The timing is influenced by v3.19 commit
|
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|---|---|---|
| .. | ||
| Makefile | ||
| zfcp_aux.c | ||
| zfcp_ccw.c | ||
| zfcp_dbf.c | ||
| zfcp_dbf.h | ||
| zfcp_def.h | ||
| zfcp_diag.c | ||
| zfcp_diag.h | ||
| zfcp_erp.c | ||
| zfcp_ext.h | ||
| zfcp_fc.c | ||
| zfcp_fc.h | ||
| zfcp_fsf.c | ||
| zfcp_fsf.h | ||
| zfcp_qdio.c | ||
| zfcp_qdio.h | ||
| zfcp_reqlist.h | ||
| zfcp_scsi.c | ||
| zfcp_sysfs.c | ||
| zfcp_unit.c | ||