[issue18078] threading.Condition to allow notify on a specific waiter

[João Bernardo]

New submission from João Bernardo:

If users could provide an inner lock for `threading.Condition` acquire when making a thread wait, it would allow for notifying a specific waiter.

Because of race conditions, using:

    cond.notify(1)

may not wake the thread I want. Also, I may not want to wake the first waiter at all.

So my proposal is something along the lines:



class Condition:
    ...

    def wait(self, timeout=None, lock=None):
        ...
        waiter = _allocate_lock() if lock is None else lock
        ...

    def notify_one(self, lock): 
        # Maybe could notify a list of locks?

        try:
            self._waiters.remove(lock)
        except ValueError:
            pass 
            # Maybe RuntimeError("Lock not waiting in this Condition")
        else:
            lock.release()

----------
components: Library (Lib)
messages: 190173
nosy: JBernardo
priority: normal
severity: normal
status: open
title: threading.Condition to allow notify on a specific waiter
type: enhancement
versions: Python 3.4

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue18078>
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