starting a thread in a nother thread

[Richard Lamboj]

hello,

just for _curiosity_. What would be if i start a thread in a nother thread and
acquire a lock in the "child" thread. Is there anything that could go wrong
if someone try to start threads in threads?

Kind Regards,

Richi

 

[Stefan Behnel]

Richard Lamboj, 27.01.2010 14:06:

just for _curiosity_. What would be if i start a thread in a nother thread and
acquire a lock in the "child" thread. Is there anything that could go wrong
if someone try to start threads in threads?

There's usually tons of things that can go wrong w.r.t. threads:

http://www.eecs.berkeley.edu/Pubs/TechRpts/2006/EECS-2006-1.pdf

However, there's nothing special to a thread that was started from another
thread, so the problems don't change.

Stefan

 

[Richard Lamboj]

Am Wednesday 27 January 2010 14:10:13 schrieb Stefan Behnel:

Richard Lamboj, 27.01.2010 14:06:

There's usually tons of things that can go wrong w.r.t. threads:

http://www.eecs.berkeley.edu/Pubs/TechRpts/2006/EECS-2006-1.pdf

However, there's nothing special to a thread that was started from another
thread, so the problems don't change.

Stefan

Hello,

i have tried a little bit around with psycopg2 and threads,

I'am sharing one connection for all threads. When i'am starting the
threads "normal" everything works without any Problem. When i'am starting the
threads from another thread than i got a "segmentation fault" - i'am using
locks. I'am sending 2048 Reqeuest at once. The "normal" Methode with one
thread for every Request needs 10 seconds. The other Methode starting a
thread and starting two other threads from this thread crashes after 10 to 40
requests with the segmentation fault error. Any Idea why? Its a 64 bit
maschine. Maybe i'am making something wrong?

Kind Regards

 

[Stefan Behnel]

Richard Lamboj, 27.01.2010 15:23:

Am Wednesday 27 January 2010 14:10:13 schrieb Stefan Behnel:

i have tried a little bit around with psycopg2 and threads,

I'am sharing one connection for all threads. When i'am starting the
threads "normal" everything works without any Problem. When i'am starting the
threads from another thread than i got a "segmentation fault"

Sounds like a bug that you might want to report to the maintainers of psycopg2.

Stefan

 

[Dennis Lee Bieber]

I'am sharing one connection for all threads. When i'am starting the

I'm not familiar with the specifications of the PostgreSQL adapters,
but does the one being used state that connections may be shared by
threads? Some db-api adapters limit one to "no shared connections", some
to "no shared cursors"... I suppose some could be even be "no shared
database" or, at the extreme, "no shared adapter module".

If it does state shared connections it may be, as has been
mentioned, a bug in the adapter.

 

[John Nagle]

Richard Lamboj, 27.01.2010 15:23:

Sounds like a bug that you might want to report to the maintainers of psycopg2.

Stefan

If a C package called from Python crashes, the package is defective.
Nothing you can do from Python should be able to cause a segmentation fault.

Google search: "Results 1 - 10 of about 29,400 for psycopg2 crash".

John Nagle

 

[Richard Lamboj]

Am Wednesday 27 January 2010 15:30:17 schrieb Stefan Behnel:

Richard Lamboj, 27.01.2010 15:23:

Sounds like a bug that you might want to report to the maintainers of
psycopg2.

Stefan

Yes i should make a bug report and thanks for your help.

Just some Debugginginfo:
[New Thread 0x429b5950 (LWP 27486)]
python-dbg: ../Objects/stringobject.c:116: PyString_FromString: Assertion
`str != ((void *)0)' failed.

Program received signal SIGABRT, Aborted.
[Switching to Thread 0x431b6950 (LWP 27484)]
0x00007f6d932feed5 in raise () from /lib/libc.so.6

 

[Aahz]

If a C package called from Python crashes, the package is defective.
Nothing you can do from Python should be able to cause a segmentation
fault.

....unless you use ctypes.