Program Hangs after --async

[jcstill]

After using --async, all subsequent commands with or without --async spawn second process and whole program hangs. I am not sure if the second process is normal as I only noticed it after having to forcefully kill ddcutil with sudo kill -9 PID.

Version 0.8.6:

Version 0.9.9:

I only got verbose outputs after this started happening (just the detect command):
Version 0.8.6:

Version 0.9.9:

Unfortunately the process is in state D (uninterruptible sleep). I assume a reboot will get rid of these and fix the problem altogether, though haven't tried yet. I will reboot and update.

[rockowitz]

Thank you for reporting the hang. There have been similar reports in the past, but never have been able to reproduce the problem.  Are you able to reproduce it?  If so, does it occur when you invoke ddcutil without using sudo? If you can reproduce the problem, try usingrecently added option <http://www.ddcutil.com/release_notes/> "--timeout-i2c-io".  This option causes most I2C IO calls to time out instead of waiting forever.  If timeout occurs, a debug message is issued to draw attention to the event. I'm not sure what you're getting at regarding the "--verbose" option.  It should cause the settings information to be shown at the start of any command with that option.

…

-- Sanford

On 7/18/20 3:21 AM, Jacob Still wrote: After using |--async|, all subsequent commands with or without |--async| spawn second process and whole program hangs. I am not sure if the second process is normal as I only noticed it after having to forcefully kill ddcutil with |sudo kill -9 PID|. Version 0.8.6: ddcutil_HEADSHOTS <https://user-images.githubusercontent.com/31301328/87847215-35645a80-c88b-11ea-8027-34ca34610a48.png> Version 0.9.9: ddcutil_HEADSHOTS_2 <https://user-images.githubusercontent.com/31301328/87847216-35fcf100-c88b-11ea-9785-77158c43cd44.png> I only got verbose outputs after this started happening (just the detect command): Version 0.8.6: ddcutil_verbose_detect <https://user-images.githubusercontent.com/31301328/87847334-3944ac80-c88c-11ea-91e3-b47b1a5febe4.png> Version 0.9.9: ddcutil_verbose_detect_2 <https://user-images.githubusercontent.com/31301328/87847335-39dd4300-c88c-11ea-80a3-621aed0ae4fd.png> Unfortunately the process is in state D (uninterruptible sleep). I assume a reboot will get rid of these and fix the problem altogether, though haven't tried yet. I will reboot and update. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#131>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADMGY3SC5MIAMZYEXX72ECDR4FEP7ANCNFSM4O7RH6MA>.

[jcstill]

Rebooting fixed the issue, as expected. However, the kernel sat waiting for those processes to end for about 15 min before I decided to cut power.

As for the verbose thing, I meant that I did not run the program with verbose before the hang, so there is no before/after reference for this machine (not sure if it matters).

I am not sure if this occurs without sudo, as I get permission denied errors. I will test if this occurs running from the root user as well.

I was able to reproduce this, though I did not document and it was almost exactly the same as:

Correct. If I call this:

/usr/bin/ddcutil -d 1 setvcp 10 50 &
/usr/bin/ddcutil -d 2 setvcp 10 50 &

The second command will hang.

However, changing it to this:

/usr/bin/ddcutil -d 1 setvcp 10 50
sleep .1
/usr/bin/ddcutil -d 2 setvcp 10 50

Has resulted in no hangs when calling the batch command.

Originally posted by @nvahalik in #86 (comment)

Ill do some more testing and document it.

[jcstill]

I think I may have been incorrect in assuming this was caused by async. It seems that async works as intended:

note: all file with "baseline" were run before running async
every run as non-priveleged user looks identical to detect_baseline_noprivs.txt
every run as root user looks identical to the respective sudo run

command	result
ddcutil -v detect	detect_baseline_noprivs.txt
sudo ddcutil -v detect	detect_baseline_sudo.txt
sudo ddcutil -v -d 2 setvcp 10 75	setvcp_baseline_sudo.txt
sudo ddcutil -v -d 2 --timeout-i2c-io setvcp 10 75	setvcp_timeout-i2c-io_sudo.txt
sudo ddcutil -v --async -d 2 setvcp 10 75	setvcp_async_baseline_sudo.txt
ddcutil -v --async --timeout-i2c-io -d 2 setvcp 10 75	setvcp_async_timeout_sudo.txt

Basically everything appears to be working as normal. Here is the interrogate:
interrogate_baseline_sudo.txt

I think this is actually the same problem as #86.

This works in a script (ran with root privs):

ddcutil -v -d 2 setvcp 10 $1
ddcutil -v -d 2 setvcp 12 $1

This causes the hang:

ddcutil -v --timeout-i2c-io -d 2 setvcp 10 $1 &
ddcutil -v --timeout-i2c-io -d 2 setvcp 12 $1 &

I will update with --async and also adding a sleep similar to what @nvahalik did to test further.

This is the script I am using:

#!/bin/bash

# Tested, Working
#ddcutil -v -d 2 setvcp 10 $1
#ddcutil -v -d 2 setvcp 12 $1

#--------------------------------------------------------

# Tested, Causes Hang
#ddcutil -v --timeout-i2c-io -d 2 setvcp 10 $1 &
#ddcutil -v --timeout-i2c-io -d 2 setvcp 12 $1 &

# Untested
ddcutil -v --timeout-i2c-io -d 2 setvcp 10 $1 &
sleep 1
ddcutil -v --timeout-i2c-io -d 2 setvcp 12 $1 &

#--------------------------------------------------------

# Untested
#ddcutil -v --async --timeout-i2c-io -d 2 setvcp 10 $1 &
#ddcutil -v --async --timeout-i2c-io -d 2 setvcp 12 $1 &

# Untested
#ddcutil -v --async --timeout-i2c-io -d 2 setvcp 10 $1 &
#sleep 1
#ddcutil -v --async --timeout-i2c-io -d 2 setvcp 12 $1 &

#--------------------------------------------------------

# Untested
#ddcutil -v --async -d 2 setvcp 10 $1 &
#ddcutil -v --async -d 2 setvcp 12 $1 &

# Untested
#ddcutil -v --async -d 2 setvcp 10 $1 &
#sleep 1
#ddcutil -v --async -d 2 setvcp 12 $1 &

[jcstill]

I tested all the cases in the script and here are the results:

async Hang:

This one was weird as the first time I ran it, nothing happened (display didn't change) and it did not hang. But, the second time hung:

async+sleep Hang

async+timeout Hang:

timeout Hang:

timeout+sleep Hang:

sleep Hang:

ddcutil -v -d 2 setvcp 10 $1 &
sleep 1
ddcutil -v -d 2 setvcp 12 $1 &

Wokring:

async+timeout+sleep Works:

[rockowitz]

Jacob, Thank you for the detailed tests.  I will review what you've observed. One minor thing to point out is that you can run ddcutil as a non-root user.  From the interrogate output, I see that group i2c exists and the /dev/i2c devices are assigned to that group, which has RW permission for the devices.  All you need to do is add your user to that group. Alternatively, and you can simply "sudo chmod a+rw /dev/i2c*", though you'll have to do this every time you log on. Regards, Sanford

…

On 7/18/20 8:59 PM, Jacob Still wrote: Rebooting fixed the issue, as expected. However, the kernel sat waiting for those processes to end for about 15 min before I decided to cut power. As for the verbose thing, I meant that I did not run the program with verbose before the hang, so there is no before/after reference for this machine (not sure if it matters). I am not sure if this occurs without sudo, as I get permission denied errors. I will test if this occurs running from the root user as well. I was able to reproduce this, though I did not document and it was almost exactly the same as: Correct. If I call this: |/usr/bin/ddcutil -d 1 setvcp 10 50 & /usr/bin/ddcutil -d 2 setvcp 10 50 & | The second command will hang. However, changing it to this: |/usr/bin/ddcutil -d 1 setvcp 10 50 sleep .1 /usr/bin/ddcutil -d 2 setvcp 10 50 | Has resulted in no hangs when calling the batch command. /Originally posted by @nvahalik <https://github.com/nvahalik> in #86 (comment) <#86 (comment)>/ Ill do some more testing and document it. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#131 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADMGY3TRGG3Y3GWEZM7H5BLR4JAOXANCNFSM4O7RH6MA>.

[jcstill]

One minor thing to point out is that you can run ddcutil as a non-root
user. From the interrogate output, I see that group i2c exists and the
/dev/i2c devices are assigned to that group, which has RW permission for
the devices. All you need to do is add your user to that group.

I guess that completely flew over my head. Makes perfect sense though. Thanks.

[rockowitz]

What your tests show is that the hang happens when running 2 instances of ddcutil in parallel (& at the end of command), not when running them sequentially.  Based on the prior email and this one, it's unclear whether inserting a sleep between the 2 sequential ddcutil calls is unnecessary. Please run a failure case with the following command options: "--trace i2c --tid --ts".  This will turn on tracing in the i2c layer, and include the thread id and timestamp. If you can, please run the tests using the current 1.0.0 branch. I've made minor changes to tracing that should make the output easier to analyze. Regards, Sanford

…

On 7/18/20 11:34 PM, Jacob Still wrote: I think I may have been incorrect in assuming this was caused by |async|. It seems that |async| works as intended: note: all file with "baseline" were run before running |async| every run as non-priveleged user looks identical to |detect_baseline_noprivs.txt| every run as root user looks identical to the respective |sudo| run command result |ddcutil -v detect| detect_baseline_noprivs.txt <https://github.com/rockowitz/ddcutil/files/4943153/detect_baseline_noprivs.txt> |sudo ddcutil -v detect| detect_baseline_sudo.txt <https://github.com/rockowitz/ddcutil/files/4943154/detect_baseline_sudo.txt> |sudo ddcutil -v -d 2 setvcp 10 75| setvcp_baseline_sudo.txt <https://github.com/rockowitz/ddcutil/files/4943159/setvcp_baseline_sudo.txt> |sudo ddcutil -v -d 2 --timeout-i2c-io setvcp 10 75| setvcp_timeout-i2c-io_sudo.txt <https://github.com/rockowitz/ddcutil/files/4943160/setvcp_timeout-i2c-io_sudo.txt> |sudo ddcutil -v --async -d 2 setvcp 10 75| setvcp_async_baseline_sudo.txt <https://github.com/rockowitz/ddcutil/files/4943157/setvcp_async_baseline_sudo.txt> |ddcutil -v --async --timeout-i2c-io -d 2 setvcp 10 75| setvcp_async_timeout_sudo.txt <https://github.com/rockowitz/ddcutil/files/4943158/setvcp_async_timeout_sudo.txt> Basically everything appears to be working as normal. Here is the interrogate: interrogate_baseline_sudo.txt <https://github.com/rockowitz/ddcutil/files/4943175/interrogate_baseline_sudo.txt> I think this is actually the same problem as #86 <#86>. This works in a script (ran with root privs): ddcutil -v -d 2 setvcp 10$1 ddcutil -v -d 2 setvcp 12$1 This causes the hang: ddcutil -v --timeout-i2c-io -d 2 setvcp 10$1 & ddcutil -v --timeout-i2c-io -d 2 setvcp 12$1 & timeout_hang_output <https://user-images.githubusercontent.com/31301328/87866280-a6138180-c934-11ea-95b0-26365bca07ca.png> timeout_hang_ps <https://user-images.githubusercontent.com/31301328/87866281-a6ac1800-c934-11ea-9534-6af75330a9e4.png> I will update with |--async| and also adding a |sleep| similar to what @nvahalik <https://github.com/nvahalik> did to test further. This is the script I am using: #!/bin/bash # Tested, Working #ddcutil -v -d 2 setvcp 10 $1 #ddcutil -v -d 2 setvcp 12 $1 #-------------------------------------------------------- # Tested, Causes Hang #ddcutil -v --timeout-i2c-io -d 2 setvcp 10 $1 & #ddcutil -v --timeout-i2c-io -d 2 setvcp 12 $1 & # Untested ddcutil -v --timeout-i2c-io -d 2 setvcp 10$1 & sleep 1 ddcutil -v --timeout-i2c-io -d 2 setvcp 12$1 & #-------------------------------------------------------- # Untested #ddcutil -v --async --timeout-i2c-io -d 2 setvcp 10 $1 & #ddcutil -v --async --timeout-i2c-io -d 2 setvcp 12 $1 & # Untested #ddcutil -v --async --timeout-i2c-io -d 2 setvcp 10 $1 & #sleep 1 #ddcutil -v --async --timeout-i2c-io -d 2 setvcp 12 $1 & #-------------------------------------------------------- # Untested #ddcutil -v --async -d 2 setvcp 10 $1 & #ddcutil -v --async -d 2 setvcp 12 $1 & # Untested #ddcutil -v --async -d 2 setvcp 10 $1 & #sleep 1 #ddcutil -v --async -d 2 setvcp 12 $1 & — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#131 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADMGY3RICQ2TFZVCIKVHCTTR4JSVPANCNFSM4O7RH6MA>.