From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54451) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uz4CN-0004MM-Bm for qemu-devel@nongnu.org; Tue, 16 Jul 2013 08:17:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Uz4CJ-0008MN-Ct for qemu-devel@nongnu.org; Tue, 16 Jul 2013 08:17:43 -0400 Received: from e06smtp13.uk.ibm.com ([195.75.94.109]:56655) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uz4CJ-0008Lt-3H for qemu-devel@nongnu.org; Tue, 16 Jul 2013 08:17:39 -0400 Received: from /spool/local by e06smtp13.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 16 Jul 2013 13:13:05 +0100 Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id 9B893219005E for ; Tue, 16 Jul 2013 13:21:33 +0100 (BST) Received: from d06av01.portsmouth.uk.ibm.com (d06av01.portsmouth.uk.ibm.com [9.149.37.212]) by b06cxnps4075.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r6GCHMSx50069624 for ; Tue, 16 Jul 2013 12:17:22 GMT Received: from d06av01.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av01.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id r6GCHX2U004786 for ; Tue, 16 Jul 2013 06:17:33 -0600 Date: Tue, 16 Jul 2013 14:17:28 +0200 From: Michael Mueller Message-ID: <20130716141728.787f6b2b@bee> In-Reply-To: <20130716030511.GF32278@stefanha-thinkpad.redhat.com> References: <1373917279-15360-1-git-send-email-borntraeger@de.ibm.com> <20130716030511.GF32278@stefanha-thinkpad.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 02/12] trace+libvirt: start trace processing thread in final child process List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Christian Borntraeger , aliguori@us.ibm.com, qemu-devel@nongnu.org, =?UTF-8?B?TGx1w61z?= On Tue, 16 Jul 2013 11:05:11 +0800 Stefan Hajnoczi wrote: > On Mon, Jul 15, 2013 at 09:41:19PM +0200, Christian Borntraeger wrote: > > When running with trace backend e.g. "simple" the writer thread > > needs to be implemented in the same process context as the trace > > points that will be processed. Under libvirtd control, qemu gets > > first started in daemonized mode to privide its capabilities. > > Creating the writer thread in the initial process context then > > leads to a dead lock because the thread gets termined together with > > the initial parent. (-daemonize) This results in stale qemu > > processes. Fix this by deferring trace initialization. > > I don't think this works since trace events will fill up trace_buf[] > and eventually invoke flush_trace_file(). > > At that point we use trace_available_cond and trace_empty_cond, which > may be NULL in Glib <2.31.0. > > Perhaps this can be made safe by checking trace_writeout_enabled. It > will be false before the backend has been initialized. > > Stefan > You mean something like this. I'll give it a try: --- trace/simple.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/trace/simple.c +++ b/trace/simple.c @@ -53,7 +53,7 @@ static GCond *trace_empty_cond; #endif static bool trace_available; -static bool trace_writeout_enabled; +static bool trace_writeout_enabled = false; enum { TRACE_BUF_LEN = 4096 * 64, @@ -427,5 +427,6 @@ bool trace_backend_init(const char *even atexit(st_flush_trace_buffer); trace_backend_init_events(events); st_set_trace_file(file); + trace_writeout_enabled = false; return true; } Michael