From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34580) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VTWME-0000sQ-Tg for qemu-devel@nongnu.org; Tue, 08 Oct 2013 08:25:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VTWM8-0005oq-UC for qemu-devel@nongnu.org; Tue, 08 Oct 2013 08:25:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:3553) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VTWM8-0005od-Mk for qemu-devel@nongnu.org; Tue, 08 Oct 2013 08:25:40 -0400 Date: Tue, 8 Oct 2013 14:25:50 +0200 From: Kevin Wolf Message-ID: <20131008122550.GD25109@dhcp-200-207.str.redhat.com> References: <1381226311-23489-1-git-send-email-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1381226311-23489-1-git-send-email-stefanha@redhat.com> Subject: Re: [Qemu-devel] [PATCH] osdep: initialize glib threads in all QEMU tools List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: mario.dechenno@unina2.it, Paolo Bonzini , qemu-devel@nongnu.org Am 08.10.2013 um 11:58 hat Stefan Hajnoczi geschrieben: > glib versions prior to 2.31.0 require an explicit g_thread_init() call > to enable multi-threading. > > Failure to initialize threading causes glib to take single-threaded code > paths without synchronization. For example, the g_slice allocator will > crash due to race conditions. > > Fix this for all QEMU tool programs (qemu-nbd, qemu-io, qemu-img) by > moving the g_thread_init() call from vl.c:main() into a new > osdep.c:thread_init() constructor function. > > thread_init() has __attribute__((constructor)) and is automatically > invoked by the runtime during startup. > > We can now drop the "simple" trace backend's g_thread_init() call since > thread_init() already called it. > > Note that we must keep coroutine-gthread.c's g_thread_init() call which > is located in a constructor function. There is no guarantee for > constructor function ordering so thread_init() may only be called later. The glib documentation says: Since version 2.24, calling g_thread_init() multiple times is allowed, but nothing happens except for the first call. I take that this means previously it wasn't allowed. qemu's configure checks for a minimum version of 2.12, so we seems to support glib versions that don't allow g_thread_init() to be called multiple times. Do we need to protect against this? Kevin