Issue #7316: the acquire() method of lock objects in the :mod:`threading`

module now takes an optional timeout argument in seconds.  Timeout support
relies on the system threading library, so as to avoid a semi-busy wait
loop.

1 files changed, 26 insertions, 2 deletions

diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst
index f642111..1f2b763 100644
--- a/Doc/library/threading.rst
+++ b/Doc/library/threading.rst
@@ -155,6 +155,16 @@ This module defines the following functions and objects:
    Availability: Windows, systems with POSIX threads.
 
 
+This module also defines the following constant:
+
+.. data:: TIMEOUT_MAX
+
+   The maximum value allowed for the *timeout* parameter of blocking functions
+   (:meth:`Lock.acquire`, :meth:`RLock.acquire`, :meth:`Condition.wait`, etc.).
+   Specifiying a timeout greater than this value will raise an
+   :exc:`OverflowError`.
+
+
 Detailed interfaces for the objects are documented below.
 
 The design of this module is loosely based on Java's threading model. However,
@@ -349,7 +359,7 @@ and may vary across implementations.
 All methods are executed atomically.
 
 
-.. method:: Lock.acquire(blocking=True)
+.. method:: Lock.acquire(blocking=True, timeout=-1)
 
    Acquire a lock, blocking or non-blocking.
 
@@ -363,6 +373,15 @@ All methods are executed atomically.
    without an argument would block, return false immediately; otherwise, do the
    same thing as when called without arguments, and return true.
 
+   When invoked with the floating-point *timeout* argument set to a positive
+   value, block for at most the number of seconds specified by *timeout*
+   and as long as the lock cannot be acquired.  A negative *timeout* argument
+   specifies an unbounded wait.  It is forbidden to specify a *timeout*
+   when *blocking* is false.
+
+   The return value is ``True`` if the lock is acquired successfully,
+   ``False`` if not (for example if the *timeout* expired).
+
 
 .. method:: Lock.release()
 
@@ -396,7 +415,7 @@ pair) resets the lock to unlocked and allows another thread blocked in
 :meth:`acquire` to proceed.
 
 
-.. method:: RLock.acquire(blocking=True)
+.. method:: RLock.acquire(blocking=True, timeout=-1)
 
    Acquire a lock, blocking or non-blocking.
 
@@ -415,6 +434,11 @@ pair) resets the lock to unlocked and allows another thread blocked in
    without an argument would block, return false immediately; otherwise, do the
    same thing as when called without arguments, and return true.
 
+   When invoked with the floating-point *timeout* argument set to a positive
+   value, block for at most the number of seconds specified by *timeout*
+   and as long as the lock cannot be acquired.  Return true if the lock has
+   been acquired, false if the timeout has elapsed.
+
 
 .. method:: RLock.release()