[Python-Dev] bpo-33257: seeking advice & approval on the course of action (original) (raw)

Ivan Pozdeev vano at mail.mipt.ru
Mon May 14 15:10:14 EDT 2018

On 14.05.2018 22:05, Ivan Pozdeev wrote:

On 14.05.2018 21:58, Terry Reedy wrote:

On 5/14/2018 12:20 PM, Chris Barker via Python-Dev wrote:

On Wed, May 2, 2018 at 8:21 PM, Terry Reedy <tjreedy at udel.edu_ _<mailto:tjreedy at udel.edu>> wrote:

On 5/2/2018 4:38 PM, Ivan Pozdeev via Python-Dev wrote: The bottom line is: Tkinter is currently broken

This is way over-stated.  Many modules have bugs, somethings in features more central to their main purpose. I'll suggest a re-statement: tkinter is not thread safe, Still over-stated.  If one uses tcl/tk compiled with thread support, tkinter is thread-safe.  This is 'as far as I know' from running posted 'failing' examples (possible with bug fixes) with 3.5+ on Windows, which is installed with tcl/tk 8.6, which defaults to thread-safe. This means that you didn't (yet) read the letter that I attached to https://bugs.python.org/issue33479 . Reciting the relevant section: === The reality is that with neither flavor of Tcl is Tkinter completely thread-safe, but with threaded flavor, it's more so: * with nonthreaded Tcl, making concurrent Tcl calls leads to crashes due to incorrect management of the "Tcl lock" as per https://bugs.python.org/issue33257 * with threaded Tcl, the only issue that I found so far is that a few APIs must be called from the interpreter's thread (https://bugs.python.org/issue33412#msg316152; so far, I know mainloop() and destroy() to be this) -- while most can be called from anywhere. Whether the exceptions are justified is a matter of discussion (e.g. at first glance, destroy() can be fixed). And another undocumented limitation for threaded Tcl: when calling anything from outside the interpreter thread, mainloop() must be running in the interpreter threads, or the call will either raise or hang (dunno any more details atm). ===

Tkinter was intended to also be thread-safe when using tcl/tk without thread support, which was the default for tcl/tk 8.5 and before. The posted examples can fail on 2.x on Windows, which comes with tcl/tk 8.5 or before. tkinter.c has some different #ifdefs for the two situations. >>> and yet it is documented as being thread safe >> True in https://docs.python.org/3/library/tk.html Unspecified in https://docs.python.org/3/library/tkinter.html >>> This is either a bug(s) in the implementation or the docs. >> Both >>> So what are the solutions? >>>> 1) fix the docs -- unless tkInter is made thread safe really soon, > and fixes are back-ported, this seems like a no brainer -- at least > temporarily. >> https://bugs.python.org/issue33479 'Document tkinter and threads' >>> 2) fix the issues that make tkInter not thread safe >> with non-thread tcl/tk. >> https://bugs.python.org/issue33257 has a patch that might improve the situation for one type of call.  Fixing everything might not be possible.  AFAIK, there are currently no tests of thread safety. >

Regards, Ivan

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