Laszlo Ersek <ler...@redhat.com> writes:
> 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 <ler...@redhat.com>
Reviewed-by: Anthony Liguori <aligu...@us.ibm.com>
Regards,
Anthony Liguori
> ---
> monitor.c | 11 +++++++++--
> 1 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/monitor.c b/monitor.c
> index 2ba7876..de24b2c 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -189,6 +189,7 @@ struct Monitor {
> int suspend_cnt;
> bool skip_flush;
> QString *outbuf;
> + guint watch;
> ReadLineState *rs;
> MonitorControl *mc;
> CPUState *mon_cpu;
> @@ -263,7 +264,10 @@ int monitor_read_password(Monitor *mon, ReadLineFunc
> *readline_func,
> 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 @@ void monitor_flush(Monitor *mon)
> 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);
> + }
> }
> }
>
> --
> 1.7.1
