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Author Topic: [Solved] reliable way to run post-suspend jobs?  (Read 251 times)

Offline GNUser

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[Solved] reliable way to run post-suspend jobs?
« on: November 21, 2020, 06:57:05 AM »
I am looking for a simple but reliable way of running pre- and post-suspend jobs.

Right now I have my Sleep Button bound to a shell script that looks like this:

Code: [Select]
#!/bin/sh

# pre-suspend jobs:
foo
bar
baz
sleep 1

# suspend:
sudo sh -c "echo mem >/sys/power/state"

# post-suspend jobs:
sleep 1
qux
quux
quuz


I've found that pre-suspend jobs run reliably but post-suspend jobs don't always run. Is there a better solution?
« Last Edit: November 21, 2020, 06:15:31 PM by Rich »

Offline Rich

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Re: reliable way to run post-suspend jobs?
« Reply #1 on: November 21, 2020, 07:33:17 AM »
Hi GNUser
When you execute this:
Code: [Select]
sudo sh -c "echo mem >/sys/power/state"it's a signal to the operating system to enter the suspend mode. Doesn't the operating system provide a signal that it
has resumed normal operations that you can test for instead of using a sleep command?

Offline GNUser

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Re: reliable way to run post-suspend jobs?
« Reply #2 on: November 21, 2020, 07:50:12 AM »
Doesn't the operating system provide a signal that it has resumed normal operations that you can test for
That would be convenient, maybe there is such a thing. I'll keep looking.

Another (very unlikely) possibility is that the kernel knows to execute shell scripts in a particular directory when it resumes from suspend?

Also, maybe Busybox init or something else in the TCL base system has hooks for post-suspend jobs?

Offline Rich

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Re: reliable way to run post-suspend jobs?
« Reply #3 on: November 21, 2020, 08:06:19 AM »
Hi GNUser
Depending on what the scripts are doing, it could be a driver that takes too long to wake up. Checking  dmesg  and
/var/log/messages  after resuming would be useful in that case.

Well I learned something new today. qux and quux are not Linux programs, they're fake names like foo and bar.

Offline curaga

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Re: reliable way to run post-suspend jobs?
« Reply #4 on: November 21, 2020, 10:00:43 AM »
This looks like a timing race? The suspend echo does not block, so the sleep and the first few commands may have executed by the time the system has suspended.
The only barriers that can stop you are the ones you create yourself.

Offline GNUser

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Re: reliable way to run post-suspend jobs?
« Reply #5 on: November 21, 2020, 10:28:59 AM »
The suspend echo does not block...
Yes, that could explain the problems I'm having. I was assuming that the echo caused the system to suspend immediately.

Well, I found that the kernel logs something like this in  /var/log/messages  after the system wakes up:
Code: [Select]
Nov 21 13:17:50 t500 user.info kernel: ACPI: Low-level resume complete
So as long as the user doesn't need anything in  /var/log/messages  from before the suspend, something like this would get around the problem:

Code: [Select]
#!/bin/sh

# pre-suspend jobs:
foo
bar
baz

# suspend:
sudo rm /var/log/messages
sudo sh -c "echo mem >/sys/power/state"

# wait for system resume to be complete:
while true; do
grep -q "resume complete" /var/log/messages && break
sleep 0.1
done

# post-suspend jobs:
qux
quux
quuz

Do you guys foresee any problems with the above strategy?
« Last Edit: November 21, 2020, 10:30:32 AM by GNUser »

Offline GNUser

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Re: reliable way to run post-suspend jobs?
« Reply #6 on: November 21, 2020, 10:45:20 AM »
It's also important to make sure that there is only one instance of the script running at a time, otherwise things can get chaotic.

So, assuming the script is called  suspend-jobs , this is the final form of the script:

Code: [Select]
#!/bin/sh

# kill other instances of this script:
kill $(pgrep -f suspend-jobs | grep -v $$) 2>/dev/null

# pre-suspend jobs:
foo
bar
baz

# suspend:
sudo sed -i '/resume complete/ d' /var/log/messages
sudo sh -c "echo mem >/sys/power/state"

# wait for system resume to be complete:
while true; do
grep -q "resume complete" /var/log/messages 2>/dev/null && break
sleep 0.1
done

# post-suspend jobs:
qux
quux
quuz

Thread may be marked as "Solved". Thank you both very much.

P.S. If anyone can think of further improvements to boost reliability, please do share.

EDIT: I changed the script so that it doesn't delete  /var/log/messages  before suspending.
« Last Edit: November 21, 2020, 11:13:59 AM by GNUser »

Offline jazzbiker

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Re: reliable way to run post-suspend jobs?
« Reply #7 on: November 21, 2020, 12:03:14 PM »
Thanks, guys! Sheer brilliant! Goliath shut down with a pinpoint! Sorry for offtopic, couldn't hide excitement...

Offline Rich

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Re: [Solved] reliable way to run post-suspend jobs?
« Reply #8 on: November 21, 2020, 06:34:12 PM »
Hi GNUser
... P.S. If anyone can think of further improvements to boost reliability, please do share.

EDIT: I changed the script so that it doesn't delete  /var/log/messages  before suspending.
So if you do  suspend/resume  and then do  suspend/resume  again, then this piece of code will succeed immediately
because it will find the  resume complete  message from the previous resume:
Code: [Select]
# wait for system resume to be complete:
while true; do
grep -q "resume complete" /var/log/messages 2>/dev/null && break
sleep 0.1
done

Offline GNUser

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Re: [Solved] reliable way to run post-suspend jobs?
« Reply #9 on: November 22, 2020, 08:09:09 PM »
Rich, that will not be a problem. Note the  sed  command in the final form of the script (in Reply #6).

jazzbiker, I share your excitement. Other distros do seem to overcomplicate this sort of thing. (Actually, now that I'm used to TCL, other distros seem to be exercises in overengineering.)
« Last Edit: November 22, 2020, 08:13:39 PM by GNUser »

Offline Rich

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Re: [Solved] reliable way to run post-suspend jobs?
« Reply #10 on: November 22, 2020, 08:17:40 PM »
Hi GNUser
Ah, I missed the  sed  command. Well done.