From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52842) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZflb-0005Zy-AU for qemu-devel@nongnu.org; Wed, 09 Sep 2015 09:50:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZZflX-0002vP-9I for qemu-devel@nongnu.org; Wed, 09 Sep 2015 09:50:27 -0400 From: Paolo Bonzini Date: Wed, 9 Sep 2015 15:49:34 +0200 Message-Id: <1441806613-13775-5-git-send-email-pbonzini@redhat.com> In-Reply-To: <1441806613-13775-1-git-send-email-pbonzini@redhat.com> References: <1441806613-13775-1-git-send-email-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PULL 04/43] 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?= , qemu-stable@nongnu.org From: An=C3=ADbal Lim=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=3Dglibc.git;a=3Dblob;f=3Dnptl/pthread_c= reate.c;h=3Dd10f4ea8004e1d8f3a268b95cc0f8d93b8d89867;hb=3DHEAD#l621 Cc: qemu-stable@nongnu.org Signed-off-by: An=C3=ADbal Lim=C3=B3n Message-Id: <1441313313-3040-1-git-send-email-anibal.limon@linux.intel.co= m> Signed-off-by: Paolo Bonzini --- cpus.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/cpus.c b/cpus.c index c1e74d9..e831aa3 100644 --- a/cpus.c +++ b/cpus.c @@ -1166,7 +1166,7 @@ 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 { --=20 2.4.3