From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56057) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gUSod-00014h-3K for qemu-devel@nongnu.org; Wed, 05 Dec 2018 03:45:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gUSoc-0002rZ-5E for qemu-devel@nongnu.org; Wed, 05 Dec 2018 03:45:55 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49578) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gUSob-0002qm-SM for qemu-devel@nongnu.org; Wed, 05 Dec 2018 03:45:54 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3EDE630BD0D1 for ; Wed, 5 Dec 2018 08:45:53 +0000 (UTC) From: Markus Armbruster References: <20181204131802.16885-1-marcandre.lureau@redhat.com> <20181204131802.16885-6-marcandre.lureau@redhat.com> Date: Wed, 05 Dec 2018 09:45:47 +0100 In-Reply-To: <20181204131802.16885-6-marcandre.lureau@redhat.com> (=?utf-8?Q?=22Marc-Andr=C3=A9?= Lureau"'s message of "Tue, 4 Dec 2018 17:18:01 +0400") Message-ID: <87zhtkz7ic.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v3 5/6] monitor: prevent inserting new monitors after cleanup List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?utf-8?Q?Marc-Andr=C3=A9?= Lureau Cc: qemu-devel@nongnu.org, Paolo Bonzini , "Dr. David Alan Gilbert" , Markus Armbruster , peterx@redhat.com Marc-Andr=C3=A9 Lureau writes: > monitor_cleanup() is one of the last things main() calls before it > returns. In the following patch, monitor_cleanup() will release the > monitor_lock during flushing. There may be pending commands to insert > new monitors, which would modify the mon_list during iteration, and > the clean-up could thus miss those new insertions. > > Add a monitor_destroyed global to check if monitor_cleanup() has been > already called. In this case, don't insert the new monitor in the > list, but free it instead. > > Signed-off-by: Marc-Andr=C3=A9 Lureau > --- > monitor.c | 19 +++++++++++++++++-- > 1 file changed, 17 insertions(+), 2 deletions(-) > > diff --git a/monitor.c b/monitor.c > index 25cf4223e8..f0256bdec5 100644 > --- a/monitor.c > +++ b/monitor.c > @@ -263,10 +263,11 @@ typedef struct QMPRequest QMPRequest; > /* QMP checker flags */ > #define QMP_ACCEPT_UNKNOWNS 1 >=20=20 > -/* Protects mon_list, monitor_qapi_event_state. */ > +/* Protects mon_list, monitor_qapi_event_state, monitor_destroyed. */ > static QemuMutex monitor_lock; > static GHashTable *monitor_qapi_event_state; > static QTAILQ_HEAD(mon_list, Monitor) mon_list; > +static bool monitor_destroyed; >=20=20 > /* Protects mon_fdsets */ > static QemuMutex mon_fdsets_lock; > @@ -4538,8 +4539,21 @@ void error_vprintf_unless_qmp(const char *fmt, va_= list ap) > static void monitor_list_append(Monitor *mon) > { > qemu_mutex_lock(&monitor_lock); > - QTAILQ_INSERT_HEAD(&mon_list, mon, entry); > + /* > + * This prevents inserting new monitors during monitor_cleanup(). > + * A cleaner solution would involve the main thread telling other > + * threads to terminate, waiting for their termination. Let's add this sentence to the commit message as well. > + */ > + if (!monitor_destroyed) { > + QTAILQ_INSERT_HEAD(&mon_list, mon, entry); > + mon =3D NULL; > + } > qemu_mutex_unlock(&monitor_lock); > + > + if (mon) { > + monitor_data_destroy(mon); > + g_free(mon); > + } > } >=20=20 > static void monitor_qmp_setup_handlers_bh(void *opaque) > @@ -4635,6 +4649,7 @@ void monitor_cleanup(void) >=20=20 > /* Flush output buffers and destroy monitors */ > qemu_mutex_lock(&monitor_lock); > + monitor_destroyed =3D true; > QTAILQ_FOREACH_SAFE(mon, &mon_list, entry, next) { > QTAILQ_REMOVE(&mon_list, mon, entry); > monitor_flush(mon); Reviewed-by: Markus Armbruster