Linux, fcntl, F_SETLEASE and signals

Chris Green cmg at dok.org
Mon Jul 26 18:40:17 CEST 2004


Jeff Epler <jepler at unpythonic.net> writes:

> What I don't see here is any handling of threads.

You're right.  I'm ignorant of the thread<->signal interaction in
python.  

>
> The SIGIO handler might be called at the same time as Python code is
> running in another thread.  That means the call to getPending can see a
> partially modified queue, or that the queue can be modified by a signal
> while getPending is running.

If I put a thread-safe mutex around the queue, that should be good
enough?  Everything that I've seen has

Py_BEGIN_ALLOW_THREADS
code
Py_END_ALLOW_THREADS

getPending()
  read from queue
interrupt while reading via signal
  read from modified queue

Is this where you were recommending Py_AddPendingCall?  Add the
pending increment when no other fields are taking place?

Are C extensions only accessed by a single thread unless they
Py_BEGIN_ALLOW_THREADS?

Thanks,
Chris
-- 
Chris Green <cmg at dok.org>
Warning: time of day goes back, taking countermeasures.




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