tree 5feedcddb69a343c95492c0c6f9b7de6bf4dedd8
parent 674595d8519fdf4f78e1a4cceb2130ffa46bcdeb
author Steffen Maier <maier@linux.ibm.com> 1526577297 +0200
committer Martin K. Petersen <martin.petersen@oracle.com> 1526657241 -0400

scsi: zfcp: workqueue: set description for port work items with their WWPN as context

As a prerequisite, complement commit 3d1cb2059d93 ("workqueue: include
workqueue info when printing debug dump of a worker task") to be usable with
kernel modules by exporting the symbol set_worker_desc().  Current built-in
user was introduced with commit ef3b101925f2 ("writeback: set worker desc to
identify writeback workers in task dumps").

Can help distinguishing work items which do not have adapter scope.
Description is printed out with task dump for debugging on WARN, BUG, panic,
or magic-sysrq [show-task-states(t)].

Example:
$ echo 0 >| /sys/bus/ccw/drivers/zfcp/0.0.1880/0x50050763031bd327/failed &
$ echo 't' >| /proc/sysrq-trigger
$ dmesg
sysrq: SysRq : Show State
  task                        PC stack   pid father
...
zfcp_q_0.0.1880 S14640  2165      2 0x02000000
Call Trace:
([<00000000009df464>] __schedule+0xbf4/0xc78)
 [<00000000009df57c>] schedule+0x94/0xc0
 [<0000000000168654>] rescuer_thread+0x33c/0x3a0
 [<000000000016f8be>] kthread+0x166/0x178
 [<00000000009e71f2>] kernel_thread_starter+0x6/0xc
 [<00000000009e71ec>] kernel_thread_starter+0x0/0xc
no locks held by zfcp_q_0.0.1880/2165.
...
kworker/u512:2  D11280  2193      2 0x02000000
Workqueue: zfcp_q_0.0.1880 zfcp_scsi_rport_work [zfcp] (zrpd-50050763031bd327)
                                                        ^^^^^^^^^^^^^^^^^^^^^
Call Trace:
([<00000000009df464>] __schedule+0xbf4/0xc78)
 [<00000000009df57c>] schedule+0x94/0xc0
 [<00000000009e50c0>] schedule_timeout+0x488/0x4d0
 [<00000000001e425c>] msleep+0x5c/0x78                  >>test code only<<
 [<000003ff8008a21e>] zfcp_scsi_rport_work+0xbe/0x100 [zfcp]
 [<0000000000167154>] process_one_work+0x3b4/0x718
 [<000000000016771c>] worker_thread+0x264/0x408
 [<000000000016f8be>] kthread+0x166/0x178
 [<00000000009e71f2>] kernel_thread_starter+0x6/0xc
 [<00000000009e71ec>] kernel_thread_starter+0x0/0xc
2 locks held by kworker/u512:2/2193:
 #0:  (name){++++.+}, at: [<0000000000166f4e>] process_one_work+0x1ae/0x718
 #1:  ((&(&port->rport_work)->work)){+.+.+.}, at: [<0000000000166f4e>] process_one_work+0x1ae/0x718
...

=============================================
Showing busy workqueues and worker pools:
workqueue zfcp_q_0.0.1880: flags=0x2000a
  pwq 512: cpus=0-255 flags=0x4 nice=0 active=1/1
    in-flight: 2193:zfcp_scsi_rport_work [zfcp]
pool 512: cpus=0-255 flags=0x4 nice=0 hung=0s workers=4 idle: 5 2354 2311

Work items with adapter scope are already identified by the workqueue name
"zfcp_q_<devbusid>" and the work item function name.

Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>