From c936709e28d97b777a2b12ac8471b64bcb72aa7b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Grubbstr=C3=B6m=20=28Grubba=29?=
<grubba@grubba.org>
Date: Tue, 9 Feb 2016 14:11:28 +0100
Subject: [PATCH] Filesystem.Monitor: Improved robustness.
It seems ADT.Heap()->peek() sometimes can index the NULL value
(cf [bug 7644]). The most likely cause is that the last element
of the heap was removed by a different thread during the call.
Inhibit propagation of the error to the caller.
Work around for [bug 7644].
---
.../Filesystem.pmod/Monitor.pmod/basic.pike | 35 ++++++++++++-------
1 file changed, 22 insertions(+), 13 deletions(-)
diff --git a/lib/modules/Filesystem.pmod/Monitor.pmod/basic.pike b/lib/modules/Filesystem.pmod/Monitor.pmod/basic.pike
index ded753a2a9..ab891b5d77 100644
--- a/lib/modules/Filesystem.pmod/Monitor.pmod/basic.pike
+++ b/lib/modules/Filesystem.pmod/Monitor.pmod/basic.pike
@@ -1490,19 +1490,28 @@ int check(int|void max_wait, int|void max_cnt,
int cnt;
int t = time();
if (sizeof(monitor_queue)) {
- Monitor m;
- while ((m = monitor_queue->peek()) && (m->next_poll <= t)) {
- cnt += check_monitor(m);
- if (!(--scan_cnt)) {
- m = monitor_queue->peek();
- break;
- }
- }
- if (m) {
- ret = m->next_poll - t;
- if (ret <= 0) ret = 1;
- } else {
- scan_cnt--;
+ // NB: peek() can apparently in some circumstances throw errors.
+ // cf [bug 7644]. The likely cause being that a different
+ // thread removed the last element during the call. Make
+ // sure not to propagate the error to the caller.
+ mixed err = catch {
+ Monitor m;
+ while ((m = monitor_queue->peek()) && (m->next_poll <= t)) {
+ cnt += check_monitor(m);
+ if (!(--scan_cnt)) {
+ m = monitor_queue->peek();
+ break;
+ }
+ }
+ if (m) {
+ ret = m->next_poll - t;
+ if (ret <= 0) ret = 1;
+ } else {
+ scan_cnt--;
+ }
+ };
+ if (err) {
+ master()->handle_error(err);
}
}
if (cnt || !scan_wait || !scan_cnt) {
--
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