Author: Remi Meier <remi.me...@gmail.com>
Branch: nogil-unsafe-2
Changeset: r90492:e32f17803824
Date: 2017-03-02 17:15 +0100
http://bitbucket.org/pypy/pypy/changeset/e32f17803824/
Log: (arigo, remi) 'fix' for potential crash
diff --git a/rpython/memory/gctransform/shadowstack.py
b/rpython/memory/gctransform/shadowstack.py
--- a/rpython/memory/gctransform/shadowstack.py
+++ b/rpython/memory/gctransform/shadowstack.py
@@ -94,6 +94,12 @@
# XXX: only visit if nursery_free was not NULL
base = (tl + tl_shadowstack._offset).address[0]
top = (tl + tl_shadowstack_top._offset).address[0]
+ if base == llmemory.NULL or top == llmemory.NULL:
+ # gctransform/shadowstack.py does not set these two fields
+ # atomically. Hence, if one is still NULL, we don't need to
+ # walk that new thread's shadowstack (XXX: compiler may reorder
+ # without barriers)
+ return
self.rootstackhook(collect_stack_root, base, top)
self._walk_thread_stack = walk_thread_stack
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