From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49290) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZXbRI-0002ZH-OR for qemu-devel@nongnu.org; Thu, 03 Sep 2015 16:48:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZXbRF-0006lK-GG for qemu-devel@nongnu.org; Thu, 03 Sep 2015 16:48:56 -0400 Received: from mga09.intel.com ([134.134.136.24]:17154) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZXbRF-0006lE-8d for qemu-devel@nongnu.org; Thu, 03 Sep 2015 16:48:53 -0400 From: =?UTF-8?q?An=C3=ADbal=20Lim=C3=B3n?= Date: Thu, 3 Sep 2015 15:48:33 -0500 Message-Id: <1441313313-3040-1-git-send-email-anibal.limon@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] [PATCH] cpus.c: qemu_mutex_lock_iothread fix race condition at cpu thread init List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: =?UTF-8?q?An=C3=ADbal=20Lim=C3=B3n?= When QEMU starts the RCU thread executes qemu_mutex_lock_thread causing error "qemu:qemu_cpu_kick_thread: No such process" and exits. This isn't occur frequently but in glibc the thread id can exist and this not guarantee that the thread is on active/running state. If is inserted a sleep(1) after newthread assignment [1] the issue appears. So not make assumption that thread exist if first_cpu->thread is set then change the validation of cpu to created that is set into cpu threads (kvm, tcg, dummy). [1] https://sourceware.org/git/?p=glibc.git;a=blob;f=nptl/pthread_create.c;h=d10f4ea8004e1d8f3a268b95cc0f8d93b8d89867;hb=HEAD#l621 Signed-off-by: Aníbal Limón --- cpus.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/cpus.c b/cpus.c index 7e4786e..05e5400 100644 --- a/cpus.c +++ b/cpus.c @@ -1171,7 +1171,7 @@ void qemu_mutex_lock_iothread(void) * TCG code execution. */ if (!tcg_enabled() || qemu_in_vcpu_thread() || - !first_cpu || !first_cpu->thread) { + !first_cpu || !first_cpu->created) { qemu_mutex_lock(&qemu_global_mutex); atomic_dec(&iothread_requesting_mutex); } else { -- 1.9.1