From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NGGJ7-00010y-0R for qemu-devel@nongnu.org; Thu, 03 Dec 2009 13:21:37 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NGGJ2-0000ro-8P for qemu-devel@nongnu.org; Thu, 03 Dec 2009 13:21:36 -0500 Received: from [199.232.76.173] (port=53534 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NGGJ1-0000rc-Us for qemu-devel@nongnu.org; Thu, 03 Dec 2009 13:21:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:3009) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NGGJ1-0003Yo-Jh for qemu-devel@nongnu.org; Thu, 03 Dec 2009 13:21:31 -0500 Date: Thu, 3 Dec 2009 16:21:21 -0200 From: Luiz Capitulino Message-ID: <20091203162121.67d9c120@doriath> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] [STAGING]: Block migration segfaults List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: jan.kiszka@siemens.com Cc: qemu-devel@nongnu.org, lirans@il.ibm.com Hi there, Got this while testing block migration in staging: """ Program terminated with signal 11, Segmentation fault. #0 0x0000000000410cf9 in monitor_vprintf (mon=0x0, fmt=0x5ae5e7 "Start full migration for %s\n", ap=0x7fff1f830a40) at /home/lcapitulino/src/aliguori-queue/monitor.c:192 192 if (mon->mc && !mon->mc->print_enabled) { """ The problem here is that init_blk_migration() calls monitor_printf() with a NULL 'mon' and the backtrace shows that this is true for the entire call chain. You probably didn't note it before because the lowest-level monitor print function would just return if the 'mon' parameter was NULL. A patch from me (4a29a in staging) changes a higher level monitor function to touch 'mon' before passing it down and here's the segfault. Now, the point is: I could give the old behavior back but I think we're hiding a bug there. Why would you call monitor_printf() with a NULL 'mon'? Anyways, the following patch adds the old behavior back just in case you want to see it working... commit 3575196202d4e54c1fc63a631ca5bd1a7778e30d Author: Luiz Capitulino Date: Thu Dec 3 15:49:16 2009 -0200 monitor: Fix block migration segfault The monitor_vprintf() function now touches the 'mon' variable before calling monitor_puts(), this causes block migration to segfault as its functions call monitor_printf() with a NULL 'mon'. This is probably hiding the real bug, but for some reason this has been the behavior for a long time. We also change monitor_print_object() to use monitor_print(), so that monitor_puts() is only called by monitor_vprintf(). Signed-off-by: Luiz Capitulino diff --git a/monitor.c b/monitor.c index b035e0b..6d0b1dd 100644 --- a/monitor.c +++ b/monitor.c @@ -171,9 +171,6 @@ static void monitor_puts(Monitor *mon, const char *str) { char c; - if (!mon) - return; - for(;;) { c = *str++; if (c == '\0') @@ -189,6 +186,9 @@ static void monitor_puts(Monitor *mon, const char *str) void monitor_vprintf(Monitor *mon, const char *fmt, va_list ap) { + if (!mon) + return; + if (mon->mc && !mon->mc->print_enabled) { qemu_error_new(QERR_UNDEFINED_ERROR); } else { @@ -269,7 +269,7 @@ static void monitor_print_qobject(Monitor *mon, const QObject *data) break; } - monitor_puts(mon, "\n"); + monitor_printf(mon, "\n"); } static void monitor_json_emitter(Monitor *mon, const QObject *data)