From: Tim Peters <tim.peters@gmail.com>
Date: Sat, 30 Mar 2002 06:20:23 +0000 (+0000)
Subject: Retract the claim that this is always safe if PyMem_{Del, DEL, Free, FREE}
X-Git-Tag: v2.3c1~6240
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=12300686ca805289a340b740856ad00139a9b3c8;p=python

Retract the claim that this is always safe if PyMem_{Del, DEL, Free, FREE}
are called without the GIL.  It's incredibly unlikely to fail, but I can't
make this bulletproof without either adding a lock for exclusion, or
giving up on growing the arena base-address vector (it would be safe if
this were a static array).
---

diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index 5ac5c35f63..500afba469 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -403,6 +403,10 @@ new_arena(void)
 		 * only make a supposed-to-succeed case fail by mistake).
 		 * Read the above 50 times before changing anything in this
 		 * block.
+		 * XXX Fudge.  This is still vulnerable:  there's nothing
+		 * XXX to stop the bad-guy thread from picking up the
+		 * XXX current value of arenas, but not indexing off of it
+		 * XXX until after the PyMem_FREE(oldarenas) below completes.
 		 */
 		uptr *oldarenas;
 		int newmax = maxarenas + (maxarenas >> 1);