From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43252) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fKyIM-0002q2-NP for qemu-devel@nongnu.org; Mon, 21 May 2018 23:49:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fKyIJ-0008S0-Kj for qemu-devel@nongnu.org; Mon, 21 May 2018 23:49:06 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:34784 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fKyIJ-0008Rw-GB for qemu-devel@nongnu.org; Mon, 21 May 2018 23:49:03 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 095F240122A3 for ; Tue, 22 May 2018 03:49:03 +0000 (UTC) Date: Tue, 22 May 2018 11:48:53 +0800 From: Peter Xu Message-ID: <20180522034853.GE17282@xz-mi> References: <20180412061108.10875-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180412061108.10875-1-peterx@redhat.com> Subject: Re: [Qemu-devel] [PATCH v3] monitor: let cur_mon be per-thread List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Paolo Bonzini , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Eric Blake , Markus Armbruster , Stefan Hajnoczi , "Dr . David Alan Gilbert" On Thu, Apr 12, 2018 at 02:11:08PM +0800, Peter Xu wrote: > In the future the monitor iothread may be accessing the cur_mon as > well (via monitor_qmp_dispatch_one()). Before we introduce a real > Out-Of-Band command, let's convert the cur_mon variable to be a > per-thread variable to make sure there won't be a race between threads. > > Note that thread variables are not initialized to a valid value when new > thread is created. However for our case we don't need to set it up, > since the cur_mon variable is only used in such a pattern: > > old_mon = cur_mon; > cur_mon = xxx; > (do something, read cur_mon if necessary in the stack) > cur_mon = old_mon; > > It plays a role as stack variable, so no need to be initialized at all. > We only need to make sure the variable won't be changed unexpectedly by > other threads. > > Signed-off-by: Peter Xu > --- > v3: > - fix code style warning from patchew > v2: > - drop qemu-thread changes Ping? -- Peter Xu