Line 154 in standard library's queue.py, in the definition of Queue.put() is: self.unfinished_tasks += 1 This line should be protected by acquiring the all_tasks_done lock. Theoretically, the increment could occur somewhere during task_done()! Additional note: Personally, I would like the increment to occur *before* instead of *after* _put(). This is because I would like to be able to implement a _put() that does not put everything. This put should be able to undo the increment. As it is, calling task_done() from put might decrease the counter to zero inadvertently.
> This line should be protected by acquiring the all_tasks_done lock. All of three of the condition variables share the same underlying lock. The increment occurs only with the lock has been acquired. > Theoretically, the increment could occur somewhere during task_done()! I don't understand what you mean. The semantics of task_done() method implies that the count gets decremented. > Personally, I would like the increment to occur *before* > instead of *after* _put(). There may be some merit to this but I don't see how it matters much since both occur within the context of the same lock being held. A user defined method can still add or subtract any number it wants from the unfinished task count. The result of +1 -5 is the same as -5 +1. I'm reluctant to change the order though because the code is already published and some user's _put code may be inspecting the unfinished tasks count. I wouldn't want to break that code without good reason.
I agree. Please close the ticket. Thanks, Patrick 2011/5/3 Raymond Hettinger <report@bugs.python.org> > > Raymond Hettinger <raymond.hettinger@gmail.com> added the comment: > > > This line should be protected by acquiring the all_tasks_done lock. > > All of three of the condition variables share the same underlying lock. > The increment occurs only with the lock has been acquired. > > > Theoretically, the increment could occur somewhere during task_done()! > > I don't understand what you mean. The semantics of task_done() method > implies that the count gets decremented. > > > Personally, I would like the increment to occur *before* > > instead of *after* _put(). > > There may be some merit to this but I don't see how it matters much since > both occur within the context of the same lock being held. A user defined > method can still add or subtract any number it wants from the unfinished > task count. The result of +1 -5 is the same as -5 +1. > > I'm reluctant to change the order though because the code is already > published and some user's _put code may be inspecting the unfinished tasks > count. I wouldn't want to break that code without good reason. > > ---------- > > _______________________________________ > Python tracker <report@bugs.python.org> > <http://bugs.python.org/issue11987> > _______________________________________ >
