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== Comment: #0 - Amartey S. Pearson <apearson@xxxxxxxxxx> - 2015-04-08 16:07:04 ==
---Problem Description---
hvcs vterm driver doesn't cleanup it's tty kref allocation on close

As a result, if the vterm device is used, closed, then hot-plug removed,
the original device (/dev/hvcsX) will never be re-used as the .destruct
method never gets called.

In the hvcs_close method, it should call tty_port_put.  This in theory
would get handled by the _cleanup method, but the _close method nulls
the tty->driver_data, therefore making the _cleanup method a noop.

I made the following change which fixed the issue for me - allowed
.destruct to be called on DLPAR remove of the adapter.

*** hvcs.c	2015-04-08 14:46:44.058208878 -0500
--- hvcs.c.old	2015-04-08 14:45:33.726199732 -0500
***************
*** 1240,1246 ****
  		tty->driver_data = NULL;
  
  		free_irq(irq, hvcsd);
- 		tty_port_put(&hvcsd->port);
  		return;
  	} else if (hvcsd->port.count < 0) {
  		printk(KERN_ERR "HVCS: vty-server@%X open_count: %d"
--- 1240,1245 ----

 
Contact Information = Amartey Pearson (apearson@xxxxxxxxxx), Steven Royer (seroyer@xxxxxxxxxx) 
 
---uname output---
Linux ip9-114-251-60 3.19.0-10-generic #10-Ubuntu SMP Mon Mar 23 16:18:35 UTC 2015 ppc64le ppc64le ppc64le GNU/Linux
 
Machine Type = 8247-22L 
 
---Debugger---
A debugger is not configured
 
---Steps to Reproduce---
 1)  Create a virtual serial device from the HMC - dynamically (make sure you have rsct etc. installed for DLPAR support).  In the example below, we created a device that provides a console to lpar 6.

chhwres -m <SYS_NAME> --id <LPAR_ID> -r virtualio --rsubtype serial -o a
-a adapter_type=client,remote_lpar_id=6,remote_slot_num=0

2) From your linux partition, you should now see a console device available.  You can use the handy '/sbin/hvcsadmin' tool to see the console.
# hvcsadmin -console 6 
vty-server@30000003 partition:6 slot:0 /dev/hvcs0 vterm-state:0

Here we can see that /dev/hvcs0 got used for lpar 6

3)  Now open the device.  We'll use 'socat' here, but you can use pretty
much anything (screen, etc).  Once open, hit Ctl+] to exit

socat STDIO,raw,echo=0,escape=0x1d /dev/hvcs0

4)  Now check your hvcsadmin -console 6 again.  the vterm-state will show 1.  Let's close it. and verify it got closed (per the vterm_state)
# hvcsadmin -close /dev/hvcs0
# hvcsadmin -console 6 
vty-server@30000003 partition:6 slot:0 /dev/hvcs0 vterm-state:0

5)  Now let's remove the device alltogether.  Go back to the HMC to do
this.  Here we will remove slot # 3 (because that's what we created
above - hence the 3000000<3> value).

chhwres -m <SYS_NAME> --id <LPAR_ID> -r virtualio --rsubtype serial -o r
-s 3

6)  Verify you no longer have a console device on your linux lpar...this will not print anything out.
# hvcsadmin -console 6 

7)  Now go ahead and re-add the device with the same command as you ran
in step #1

8)  Now let's see what device it allocated.  If this were behaving correctly, it would re-allocate /dev/hvcs0, but as you'll see, it allocates /dev/hvcs1 instead.
# hvcsadmin -console 6 
vty-server@30000003 partition:6 slot:0 /dev/hvcs1 vterm-state:0

9)  You can keep repeating these until you run out of hvcsX devices.   Note that if you skipped the 'open' step, and simply removed the device then re-created it, the bug would not occur.
 
If things are working correctly, you should see the following dmesg output:
[ 5287.993312] HVCS: vty-server@30000003 added to the vio bus.
[ 5287.993326] rpadlpar_io: slot U8247.22L.2125D7A-V1-C3 added
[ 5393.109677] HVCS: vty-server@30000003 connection opened.
[ 5402.237382] HVCS: Closed vty-server@30000003 and partner vty@30000000:6 connection.
[ 5412.637292] HVCS: Destroyed hvcs_struct for vty-server@30000003.   <----- This is missing with the current driver
[ 5412.637298] HVCS: vty-server@30000003 removed from the vio bus.
[ 5412.637355] rpadlpar_io: slot U8247.22L.2125D7A-V1-C3 removed
[ 5417.069910] HVCS: vty-server@30000003 added to the vio bus.
[ 5417.069921] rpadlpar_io: slot U8247.22L.2125D7A-V1-C3 added


Stack trace output:
 no
 
Oops output:
 no
 
System Dump Info:
  The system is not configured to capture a system dump.
 
*Additional Instructions for Amartey Pearson (apearson@xxxxxxxxxx), Steven Royer (seroyer@xxxxxxxxxx): 
-Attach sysctl -a output output to the bug.

== Comment: #10 - Thierry Fauck <thierry.fauck@xxxxxxxxxx> - 2015-11-30
04:55:37 ==

** Affects: linux (Ubuntu)
     Importance: Undecided
     Assignee: Taco Screen team (taco-screen-team)
         Status: New


** Tags: architecture-ppc64le bot-comment bugnameltc-123745 severity-high targetmilestone-inin1504
-- 
hvcs vterm driver doesn't cleanup it's tty kref allocation on close
https://bugs.launchpad.net/bugs/1521123
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