[Maya-Python] Segmentation Fault Catch

[Kurian O.S]

Hey Guys,

I have a python script and it will loop through bunch of maya files and do
some stuff. But some time maya get seg fault and my script will stop there.
I tried with signal and multiprocess. But both failed

def sig_handler(signum, frame):
pass

signal.signal(signal.SIGSEGV, sig_handler)


from multiprocessing import Process, Queue
p = Process(target=startCrawling, args=(args, options))
p.start()
p.join()

Both failed.

Any other method which can trap seg fault and continue with next ?

Thanks

[Marcus Ottosson]

Hi Kurian,

Do you mean you are running separate processes that open up Maya in the
background to do some processing?

Have a look at subprocess.Popen
<https://docs.python.org/2/library/subprocess.html#subprocess.Popen>, it
runs a process completely separate from where you ran it from and shouldn't
be affected by any of them crashing. They can also be run concurrenctly, by
just running many of them at the same time. You'll be given a handle to the
process where you can either communicate or just wait (join), similar to
Process().

Best,
Marcus

Post by Kurian O.S
Hey Guys,
I have a python script and it will loop through bunch of maya files and do
some stuff. But some time maya get seg fault and my script will stop there.
I tried with signal and multiprocess. But both failed
pass
signal.signal(signal.SIGSEGV, sig_handler)
from multiprocessing import Process, Queue
p = Process(target=startCrawling, args=(args, options))
p.start()
p.join()
Both failed.
Any other method which can trap seg fault and continue with next ?
Thanks
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[Kurian O.S]

I got a hint that I was using signal.signal(signal.SIGSEGV, sig_handler)
in wrong place.

Post by Marcus Ottosson
Hi Kurian,
Do you mean you are running separate processes that open up Maya in the
background to do some processing?
Have a look at subprocess.Popen
<https://docs.python.org/2/library/subprocess.html#subprocess.Popen>, it
runs a process completely separate from where you ran it from and shouldn't
be affected by any of them crashing. They can also be run concurrenctly, by
just running many of them at the same time. You'll be given a handle to the
process where you can either communicate or just wait (join), similar to
Process().
Best,
Marcus

Post by Kurian O.S
Hey Guys,
I have a python script and it will loop through bunch of maya files and
do some stuff. But some time maya get seg fault and my script will stop
there. I tried with signal and multiprocess. But both failed
pass
signal.signal(signal.SIGSEGV, sig_handler)
from multiprocessing import Process, Queue
p = Process(target=startCrawling, args=(args, options))
p.start()
p.join()
Both failed.
Any other method which can trap seg fault and continue with next ?
Thanks
--
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[Kurian O.S]

I was wrong its not working :(

def sig_handler(signum, frame):
pass

def dosome(args, options):
#here is my seg fault coming
signal.signal(signal.SIGSEGV, sig_handler)
#maya functions goes here

if __name__ == "__main__":
from multiprocessing import Process, Queue
p = Process(target=dosome, args=(args, options))
p.start()
p.join()

This is my code

Post by Kurian O.S
I got a hint that I was using signal.signal(signal.SIGSEGV, sig_handler)
in wrong place.

Post by Marcus Ottosson
Hi Kurian,
Do you mean you are running separate processes that open up Maya in the
background to do some processing?
Have a look at subprocess.Popen
<https://docs.python.org/2/library/subprocess.html#subprocess.Popen>, it
runs a process completely separate from where you ran it from and shouldn't
be affected by any of them crashing. They can also be run concurrenctly, by
just running many of them at the same time. You'll be given a handle to the
process where you can either communicate or just wait (join), similar to
Process().
Best,
Marcus

Post by Kurian O.S
Hey Guys,
I have a python script and it will loop through bunch of maya files and
do some stuff. But some time maya get seg fault and my script will stop
there. I tried with signal and multiprocess. But both failed
pass
signal.signal(signal.SIGSEGV, sig_handler)
from multiprocessing import Process, Queue
p = Process(target=startCrawling, args=(args, options))
p.start()
p.join()
Both failed.
Any other method which can trap seg fault and continue with next ?
Thanks
--
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[Justin Israel]

Hey Kurian,

I'm not clear on this from your code example, but are you using the
multiprocessing module from within Maya? Your example indicates that it is
a standalone script. First, I don't think it is safe to use the
multiprocessing module within Maya, since forking is not a very safe thing
to do in that environment. And second, if you are going to handle the seg
fault yourself, you would be expected to exit the process afterwards (since
you aren't really doing anything to fix the problem), otherwise you are
just going to make it continue having problems.

I think you should go the route that Marcus suggested, where you use
subprocess. This will fork and exec a new process, instead of just forking
your current image, which could lead to tons of problems in Maya.

Post by Kurian O.S
I was wrong its not working :(
pass
#here is my seg fault coming
signal.signal(signal.SIGSEGV, sig_handler)
#maya functions goes here
from multiprocessing import Process, Queue
p = Process(target=dosome, args=(args, options))
p.start()
p.join()
This is my code

Post by Kurian O.S
I got a hint that I was using signal.signal(signal.SIGSEGV, sig_handler)
in wrong place.

Post by Marcus Ottosson
Hi Kurian,
Do you mean you are running separate processes that open up Maya in the
background to do some processing?
Have a look at subprocess.Popen
<https://docs.python.org/2/library/subprocess.html#subprocess.Popen>,
it runs a process completely separate from where you ran it from and
shouldn't be affected by any of them crashing. They can also be run
concurrenctly, by just running many of them at the same time. You'll be
given a handle to the process where you can either communicate or just wait
(join), similar to Process().
Best,
Marcus

Post by Kurian O.S
Hey Guys,
I have a python script and it will loop through bunch of maya files and
do some stuff. But some time maya get seg fault and my script will stop
there. I tried with signal and multiprocess. But both failed
pass
signal.signal(signal.SIGSEGV, sig_handler)
from multiprocessing import Process, Queue
p = Process(target=startCrawling, args=(args, options))
p.start()
p.join()
Both failed.
Any other method which can trap seg fault and continue with next ?
Thanks
--
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[Kurian O.S]

Hey Guys,

First its a command line tool using optparse to get arguments and options
from user and using maya standalone to do some process ( running through
mayapy ). So Some files its just fail to do the process. Subprocess I am
not sure how I can call a function with arguments.

Post by Justin Israel
Hey Kurian,
I'm not clear on this from your code example, but are you using the
multiprocessing module from within Maya? Your example indicates that it is
a standalone script. First, I don't think it is safe to use the
multiprocessing module within Maya, since forking is not a very safe thing
to do in that environment. And second, if you are going to handle the seg
fault yourself, you would be expected to exit the process afterwards (since
you aren't really doing anything to fix the problem), otherwise you are
just going to make it continue having problems.
I think you should go the route that Marcus suggested, where you use
subprocess. This will fork and exec a new process, instead of just forking
your current image, which could lead to tons of problems in Maya.

Post by Kurian O.S
I was wrong its not working :(
pass
#here is my seg fault coming
signal.signal(signal.SIGSEGV, sig_handler)
#maya functions goes here
from multiprocessing import Process, Queue
p = Process(target=dosome, args=(args, options))
p.start()
p.join()
This is my code

Post by Kurian O.S
I got a hint that I was using signal.signal(signal.SIGSEGV, sig_handler)
in wrong place.

Post by Marcus Ottosson
Hi Kurian,
Do you mean you are running separate processes that open up Maya in the
background to do some processing?
Have a look at subprocess.Popen
<https://docs.python.org/2/library/subprocess.html#subprocess.Popen>,
it runs a process completely separate from where you ran it from and
shouldn't be affected by any of them crashing. They can also be run
concurrenctly, by just running many of them at the same time. You'll be
given a handle to the process where you can either communicate or just wait
(join), similar to Process().
Best,
Marcus

Post by Kurian O.S
Hey Guys,
I have a python script and it will loop through bunch of maya files
and do some stuff. But some time maya get seg fault and my script will stop
there. I tried with signal and multiprocess. But both failed
pass
signal.signal(signal.SIGSEGV, sig_handler)
from multiprocessing import Process, Queue
p = Process(target=startCrawling, args=(args, options))
p.start()
p.join()
Both failed.
Any other method which can trap seg fault and continue with next ?
Thanks
--
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[Justin Israel]

Well if you want to stick with the multiprocessing module and just endure
the possible seg faults and some files not getting processed, you could
print a warning and then do a os._exit(1) to just terminate the process.

Using subprocess, you could have your script take arguments, such as a
-file flag to accept the file to process. When you run it without that
particular flag it would start your batch operation, and then subprocesses
can call the same executable again with specific -file options. Here would
be a pretty crude example:

#!/usr/bin/env python
import sysimport subprocess
def process(f):
print "process:", f
if __name__ == "__main__":
if '-file' in sys.argv:
process(sys.argv[-1])
sys.exit()

for names in ('foo', 'bar', 'baz'):
cmd = [sys.argv[0], '-file', names]
# cmd = [sys.executable, sys.argv[0], '-file', names]
subprocess.Popen(cmd)

​
If your script is already executable, then you wouldn't need that commented
line that runs it with "python <script>".
You would want to actually do this in a bounded way, like using a thread
pool or threads+queue to chew on your list of files to process.

Normally the multiprocessing module could work for what you are doing, but
I think it isn't playing nice with Maya's initialized environment when the
process forks.

Post by Kurian O.S
Hey Guys,
First its a command line tool using optparse to get arguments and options
from user and using maya standalone to do some process ( running through
mayapy ). So Some files its just fail to do the process. Subprocess I am
not sure how I can call a function with arguments.

Post by Justin Israel
Hey Kurian,
I'm not clear on this from your code example, but are you using the
multiprocessing module from within Maya? Your example indicates that it is
a standalone script. First, I don't think it is safe to use the
multiprocessing module within Maya, since forking is not a very safe thing
to do in that environment. And second, if you are going to handle the seg
fault yourself, you would be expected to exit the process afterwards (since
you aren't really doing anything to fix the problem), otherwise you are
just going to make it continue having problems.
I think you should go the route that Marcus suggested, where you use
subprocess. This will fork and exec a new process, instead of just forking
your current image, which could lead to tons of problems in Maya.

Post by Kurian O.S
I was wrong its not working :(
pass
#here is my seg fault coming
signal.signal(signal.SIGSEGV, sig_handler)
#maya functions goes here
from multiprocessing import Process, Queue
p = Process(target=dosome, args=(args, options))
p.start()
p.join()
This is my code

Post by Kurian O.S
I got a hint that I was using signal.signal(signal.SIGSEGV,
sig_handler) in wrong place.
On Fri, Sep 5, 2014 at 11:20 AM, Marcus Ottosson <

Post by Marcus Ottosson
Hi Kurian,
Do you mean you are running separate processes that open up Maya in
the background to do some processing?
Have a look at subprocess.Popen
<https://docs.python.org/2/library/subprocess.html#subprocess.Popen>,
it runs a process completely separate from where you ran it from and
shouldn't be affected by any of them crashing. They can also be run
concurrenctly, by just running many of them at the same time. You'll be
given a handle to the process where you can either communicate or just wait
(join), similar to Process().
Best,
Marcus

Post by Kurian O.S
Hey Guys,
I have a python script and it will loop through bunch of maya files
and do some stuff. But some time maya get seg fault and my script will stop
there. I tried with signal and multiprocess. But both failed
pass
signal.signal(signal.SIGSEGV, sig_handler)
from multiprocessing import Process, Queue
p = Process(target=startCrawling, args=(args, options))
p.start()
p.join()
Both failed.
Any other method which can trap seg fault and continue with next ?
Thanks
--
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[Kurian O.S]

I think I am confusing you all

Here is a snippet

http://pastebin.com/J526ftrM

I tried my max to explain :)

Post by Justin Israel
Well if you want to stick with the multiprocessing module and just endure
the possible seg faults and some files not getting processed, you could
print a warning and then do a os._exit(1) to just terminate the process.
Using subprocess, you could have your script take arguments, such as a
-file flag to accept the file to process. When you run it without that
particular flag it would start your batch operation, and then subprocesses
can call the same executable again with specific -file options. Here would
#!/usr/bin/env python
import sysimport subprocess
print "process:", f
process(sys.argv[-1])
sys.exit()
cmd = [sys.argv[0], '-file', names]
# cmd = [sys.executable, sys.argv[0], '-file', names]
subprocess.Popen(cmd)
​
If your script is already executable, then you wouldn't need that
commented line that runs it with "python <script>".
You would want to actually do this in a bounded way, like using a thread
pool or threads+queue to chew on your list of files to process.
Normally the multiprocessing module could work for what you are doing, but
I think it isn't playing nice with Maya's initialized environment when the
process forks.

Post by Kurian O.S
Hey Guys,
First its a command line tool using optparse to get arguments and options
from user and using maya standalone to do some process ( running through
mayapy ). So Some files its just fail to do the process. Subprocess I am
not sure how I can call a function with arguments.

Post by Justin Israel
Hey Kurian,
I'm not clear on this from your code example, but are you using the
multiprocessing module from within Maya? Your example indicates that it is
a standalone script. First, I don't think it is safe to use the
multiprocessing module within Maya, since forking is not a very safe thing
to do in that environment. And second, if you are going to handle the seg
fault yourself, you would be expected to exit the process afterwards (since
you aren't really doing anything to fix the problem), otherwise you are
just going to make it continue having problems.
I think you should go the route that Marcus suggested, where you use
subprocess. This will fork and exec a new process, instead of just forking
your current image, which could lead to tons of problems in Maya.

Post by Kurian O.S
I was wrong its not working :(
pass
#here is my seg fault coming
signal.signal(signal.SIGSEGV, sig_handler)
#maya functions goes here
from multiprocessing import Process, Queue
p = Process(target=dosome, args=(args, options))
p.start()
p.join()
This is my code

Post by Kurian O.S
I got a hint that I was using signal.signal(signal.SIGSEGV,
sig_handler) in wrong place.
On Fri, Sep 5, 2014 at 11:20 AM, Marcus Ottosson <

Post by Marcus Ottosson
Hi Kurian,
Do you mean you are running separate processes that open up Maya in
the background to do some processing?
Have a look at subprocess.Popen
<https://docs.python.org/2/library/subprocess.html#subprocess.Popen>,
it runs a process completely separate from where you ran it from and
shouldn't be affected by any of them crashing. They can also be run
concurrenctly, by just running many of them at the same time. You'll be
given a handle to the process where you can either communicate or just wait
(join), similar to Process().
Best,
Marcus

Post by Kurian O.S
Hey Guys,
I have a python script and it will loop through bunch of maya files
and do some stuff. But some time maya get seg fault and my script will stop
there. I tried with signal and multiprocess. But both failed
pass
signal.signal(signal.SIGSEGV, sig_handler)
from multiprocessing import Process, Queue
p = Process(target=startCrawling, args=(args, options))
p.start()
p.join()
Both failed.
Any other method which can trap seg fault and continue with next ?
Thanks
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[Justin Israel]

That does explain what you are trying to do, thanks. It wasn't what I
thought you were explaining.

Why do you need a Process for this? You create one process, and join on it.
Why not just initialize maya standalone right before you are going to start
the work and do it all in the original process?

As for the segfault, I don't think you can do what you are thinking. You
usually can't just ignore a segfault and keep going unless you know how to
fix the problem. The maya runtime might be in a bad state at this point and
is expecting to crash, but you are catching that. It isn't like a type of
Python exception that you can try/except and pass. Handling a SIGSEGV is
normally something you do to either do a graceful exit, or for debugging
purposes to examine the current state of the process.

Post by Kurian O.S
I think I am confusing you all
Here is a snippet
http://pastebin.com/J526ftrM
I tried my max to explain :)

Post by Justin Israel
Well if you want to stick with the multiprocessing module and just endure
the possible seg faults and some files not getting processed, you could
print a warning and then do a os._exit(1) to just terminate the process.
Using subprocess, you could have your script take arguments, such as a
-file flag to accept the file to process. When you run it without that
particular flag it would start your batch operation, and then subprocesses
can call the same executable again with specific -file options. Here would
#!/usr/bin/env python
import sysimport subprocess
print "process:", f
process(sys.argv[-1])
sys.exit()
cmd = [sys.argv[0], '-file', names]
# cmd = [sys.executable, sys.argv[0], '-file', names]
subprocess.Popen(cmd)
​
If your script is already executable, then you wouldn't need that
commented line that runs it with "python <script>".
You would want to actually do this in a bounded way, like using a thread
pool or threads+queue to chew on your list of files to process.
Normally the multiprocessing module could work for what you are doing,
but I think it isn't playing nice with Maya's initialized environment when
the process forks.

Post by Kurian O.S
Hey Guys,
First its a command line tool using optparse to get arguments and
options from user and using maya standalone to do some process ( running
through mayapy ). So Some files its just fail to do the process. Subprocess
I am not sure how I can call a function with arguments.

Post by Justin Israel
Hey Kurian,
I'm not clear on this from your code example, but are you using the
multiprocessing module from within Maya? Your example indicates that it is
a standalone script. First, I don't think it is safe to use the
multiprocessing module within Maya, since forking is not a very safe thing
to do in that environment. And second, if you are going to handle the seg
fault yourself, you would be expected to exit the process afterwards (since
you aren't really doing anything to fix the problem), otherwise you are
just going to make it continue having problems.
I think you should go the route that Marcus suggested, where you use
subprocess. This will fork and exec a new process, instead of just forking
your current image, which could lead to tons of problems in Maya.

Post by Kurian O.S
I was wrong its not working :(
pass
#here is my seg fault coming
signal.signal(signal.SIGSEGV, sig_handler)
#maya functions goes here
from multiprocessing import Process, Queue
p = Process(target=dosome, args=(args, options))
p.start()
p.join()
This is my code

Post by Kurian O.S
I got a hint that I was using signal.signal(signal.SIGSEGV,
sig_handler) in wrong place.
On Fri, Sep 5, 2014 at 11:20 AM, Marcus Ottosson <

Post by Marcus Ottosson
Hi Kurian,
Do you mean you are running separate processes that open up Maya in
the background to do some processing?
Have a look at subprocess.Popen
<https://docs.python.org/2/library/subprocess.html#subprocess.Popen>,
it runs a process completely separate from where you ran it from and
shouldn't be affected by any of them crashing. They can also be run
concurrenctly, by just running many of them at the same time. You'll be
given a handle to the process where you can either communicate or just wait
(join), similar to Process().
Best,
Marcus

Post by Kurian O.S
Hey Guys,
I have a python script and it will loop through bunch of maya files
and do some stuff. But some time maya get seg fault and my script will stop
there. I tried with signal and multiprocess. But both failed
pass
signal.signal(signal.SIGSEGV, sig_handler)
from multiprocessing import Process, Queue
p = Process(target=startCrawling, args=(args, options))
p.start()
p.join()
Both failed.
Any other method which can trap seg fault and continue with next ?
Thanks
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