[Import-sig] Imports with hooks not thread safe?

[Anthony Tuininga]

I just joined this list so my apologies if this has been discussed
before. The list (from the archives) seems close to dead with a
suggestion to kill it permanently.... :-)

I noticed that in PyImport_ImportModuleEx, that a lock is held until the
import is completed or an exception is raised. The only problem is that
the higher level interface PyImport_Import does __NOT__ hold the lock
and this is the method that is used for hooks. The builtin function
__import__ calls PyImport_ImportModuleEx but if that function is
replaced with a call to a hook, no locking takes place which makes the
import mechanism not thread safe.

My question is: would there be a problem with holding the lock during
PyImport_Import? If there is, would there be a problem with exposing a
method that would do the import lock? The only thing that is currently
available is imp.lock_held() but that simply states whether or not the
import lock is held and nothing that I could see provides any mechanism
for acquiring the import lock.

I am using Installer (from Gordon McMillan) and it is using its own
locking mechanism which seems to break inside PythonCOM (from Mark
Hammond) if a large enough quantity of threads are executing. All of my
imports are done within the import of the main module which is done
using the normal method but I would like to solve this problem in a more
permanent way as otherwise I will have to fork Installer for our own
internal use. Blech.

-- 
Anthony Tuininga
anthony@computronix.com
 
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