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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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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.