monitor: maintain at most one G_IO_OUT watch
When monitor_flush() is invoked repeatedly outside the monitor_unblocked()
callback, for example from tlb_info() -> ... -> print_pte(), several
watches may be added for the same event.
This is no problem per se because the extra monitor_unblocked() callbacks
are harmless if mon->outbuf is empty, the watches will be removed
gradually. However a big number of watches can grow "gpollfds" without
limit in glib_pollfds_fill(), triggering a -1/EINVAL condition in
g_poll().
Keep at most one such watch, by following the pattern observable in eg.
commits c874ea97 and c3d6b96e. The change has no effect when
monitor_unblocked() calls monitor_flush() (when the watch can either be
removed or renewed 1-for-1), but non-callback contexts won't create an
additional watch when the monitor already has one.
Related RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=970047
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Message-id: 1373998781-29561-3-git-send-email-lersek@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/monitor.c b/monitor.c
index 99b6ed9..6db2ba4 100644
--- a/monitor.c
+++ b/monitor.c
@@ -189,6 +189,7 @@
int suspend_cnt;
bool skip_flush;
QString *outbuf;
+ guint watch;
ReadLineState *rs;
MonitorControl *mc;
CPUState *mon_cpu;
@@ -263,7 +264,10 @@
static gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond,
void *opaque)
{
- monitor_flush(opaque);
+ Monitor *mon = opaque;
+
+ mon->watch = 0;
+ monitor_flush(mon);
return FALSE;
}
@@ -294,7 +298,10 @@
QDECREF(mon->outbuf);
mon->outbuf = tmp;
}
- qemu_chr_fe_add_watch(mon->chr, G_IO_OUT, monitor_unblocked, mon);
+ if (mon->watch == 0) {
+ mon->watch = qemu_chr_fe_add_watch(mon->chr, G_IO_OUT,
+ monitor_unblocked, mon);
+ }
}
}
