From 4709d3e1c493536e6e3058ae15de0d86c01e417a Mon Sep 17 00:00:00 2001
From: Simon Marlow <marlowsd@gmail.com>
Date: Mon, 20 Aug 2012 13:52:07 +0100
Subject: [PATCH] Retain ordering of finalizers during GC (#7160)
This came up since the addition of C finalizers, since Haskell
finalizers are already stored in an explicit list. C finalizers on
the other hand get a WEAK object each, so in order to run them in the
right order we have to make sure that list stays in the correct
order. I hate adding new invariants, but this is the quickest way to
fix the bug for now. A better way to fix it would be to have a single
WEAK object with a list of finaliers attached to it, and a primop
for adding finalizers to the list.
MERGED from commit cec899d9fb668d4adccf731a63902e5be49f0660
---
rts/sm/MarkWeak.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/rts/sm/MarkWeak.c b/rts/sm/MarkWeak.c
index f9275ecb62c4..b7d6226ee75d 100644
--- a/rts/sm/MarkWeak.c
+++ b/rts/sm/MarkWeak.c
@@ -78,6 +78,7 @@ static WeakStage weak_stage;
/* Weak pointers
*/
StgWeak *old_weak_ptr_list; // also pending finaliser list
+StgWeak *weak_ptr_list_tail;
// List of threads found to be unreachable
StgTSO *resurrected_threads;
@@ -90,6 +91,7 @@ initWeakForGC(void)
{
old_weak_ptr_list = weak_ptr_list;
weak_ptr_list = NULL;
+ weak_ptr_list_tail = NULL;
weak_stage = WeakPtrs;
resurrected_threads = END_TSO_QUEUE;
}
@@ -139,11 +141,18 @@ traverseWeakPtrList(void)
evacuate(&w->finalizer);
// remove this weak ptr from the old_weak_ptr list
*last_w = w->link;
- // and put it on the new weak ptr list
- next_w = w->link;
- w->link = weak_ptr_list;
- weak_ptr_list = w;
- flag = rtsTrue;
+ next_w = w->link;
+
+ // and put it on the new weak ptr list.
+ // NB. we must retain the order of the weak_ptr_list (#7160)
+ if (weak_ptr_list == NULL) {
+ weak_ptr_list = w;
+ } else {
+ weak_ptr_list_tail->link = w;
+ }
+ weak_ptr_list_tail = w;
+ w->link = NULL;
+ flag = rtsTrue;
debugTrace(DEBUG_weak,
"weak pointer still alive at %p -> %p",
--
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