Author: Armin Rigo <[email protected]>
Branch: gc-minimark-pinning
Changeset: r55063:fde38e1e3a87
Date: 2012-05-12 19:10 +0200
http://bitbucket.org/pypy/pypy/changeset/fde38e1e3a87/
Log: Documentation.
diff --git a/pypy/rlib/rgc.py b/pypy/rlib/rgc.py
--- a/pypy/rlib/rgc.py
+++ b/pypy/rlib/rgc.py
@@ -19,9 +19,26 @@
pass
def pin(obj):
+ """If 'obj' can move, then attempt to temporarily fix it. This
+ function returns True if and only if 'obj' could be pinned; this is
+ a special state in the GC. Note that can_move(obj) still returns
+ True even on pinned objects, because once unpinned it will indeed be
+ able to move again. In other words, the code that succeeded in
+ pinning 'obj' can assume that it won't move until the corresponding
+ call to unpin(obj), despite can_move(obj) still being True. (This
+ is important if multiple threads try to os.write() the same string:
+ only one of them will succeed in pinning the string.)
+
+ Note that this can return False for any reason, e.g. if the 'obj' is
+ already non-movable or already pinned, if the GC doesn't support
+ pinning, or if there are too many pinned objects.
+ """
return False
def unpin(obj):
+ """Unpin 'obj', allowing it to move again.
+ Must only be called after a call to pin(obj) returned True.
+ """
raise AssertionError("pin() always returns False, "
"so unpin() should not be called")
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