CLEANUP: dns: always detach the appctx from the dns session on release
When dns_session_release() calls dns_session_free(), it was shown that
it might still be attached there:
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00000000006437d7 in dns_session_free (ds=0x7f895439e810) at src/dns.c:768
768 BUG_ON(!LIST_ISEMPTY(&ds->ring.waiters));
[Current thread is 1 (Thread 0x7f895bbe2700 (LWP 31792))]
(gdb) bt
#0 0x00000000006437d7 in dns_session_free (ds=0x7f895439e810) at src/dns.c:768
#1 0x0000000000643ab8 in dns_session_release (appctx=0x7f89545a4ff0) at src/dns.c:805
#2 0x000000000062e35a in si_applet_release (si=0x7f89545a5550) at include/haproxy/stream_interface.h:236
#3 0x000000000063150f in stream_int_shutw_applet (si=0x7f89545a5550) at src/stream_interface.c:1697
#4 0x0000000000640ab8 in si_shutw (si=0x7f89545a5550) at include/haproxy/stream_interface.h:437
#5 0x0000000000643103 in dns_session_io_handler (appctx=0x7f89545a4ff0) at src/dns.c:725
#6 0x00000000006d776f in task_run_applet (t=0x7f89545a5100, context=0x7f89545a4ff0, state=81924) at src/applet.c:90
#7 0x000000000068b82b in run_tasks_from_lists (budgets=0x7f895bbbf5c0) at src/task.c:611
#8 0x000000000068c258 in process_runnable_tasks () at src/task.c:850
#9 0x0000000000621e61 in run_poll_loop () at src/haproxy.c:2636
#10 0x0000000000622328 in run_thread_poll_loop (data=0x8d7440 <ha_thread_info+64>) at src/haproxy.c:2807
#11 0x00007f895c54a06b in start_thread () from /lib64/libpthread.so.0
#12 0x00007f895bf3772f in clone () from /lib64/libc.so.6
(gdb) p &ds->ring.waiters
$1 = (struct list *) 0x7f895439e8a8
(gdb) p ds->ring.waiters
$2 = {
n = 0x7f89545a5078,
p = 0x7f89545a5078
}
(gdb) p ds->ring.waiters->n
$3 = (struct list *) 0x7f89545a5078
(gdb) p *ds->ring.waiters->n
$4 = {
n = 0x7f895439e8a8,
p = 0x7f895439e8a8
}
Let's always detach it before freeing so that it remains possible to
check the dns_session's ring before releasing it, and possibly catch
bugs.
diff --git a/src/dns.c b/src/dns.c
index 63bb52f..baafe84 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -775,6 +775,14 @@
if (!ds)
return;
+ /* We do not call ring_appctx_detach here
+ * because we want to keep readers counters
+ * to retry a conn with a different appctx.
+ */
+ HA_RWLOCK_WRLOCK(DNS_LOCK, &ds->ring.lock);
+ LIST_DEL_INIT(&appctx->wait_entry);
+ HA_RWLOCK_WRUNLOCK(DNS_LOCK, &ds->ring.lock);
+
dss = ds->dss;
HA_SPIN_LOCK(DNS_LOCK, &dss->lock);
@@ -808,13 +816,6 @@
return;
}
- /* We do not call ring_appctx_detach here
- * because we want to keep readers counters
- * to retry a con with a different appctx*/
- HA_RWLOCK_WRLOCK(DNS_LOCK, &ds->ring.lock);
- LIST_DEL_INIT(&appctx->wait_entry);
- HA_RWLOCK_WRUNLOCK(DNS_LOCK, &ds->ring.lock);
-
/* if there is no pending complete response
* message, ensure to reset
* message offsets if the session