From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36122) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZAZjx-0003Ql-8a for qemu-devel@nongnu.org; Thu, 02 Jul 2015 04:21:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZAZjt-00030b-7e for qemu-devel@nongnu.org; Thu, 02 Jul 2015 04:21:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59709) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZAZjt-00030X-26 for qemu-devel@nongnu.org; Thu, 02 Jul 2015 04:20:57 -0400 From: Paolo Bonzini Date: Thu, 2 Jul 2015 10:20:43 +0200 Message-Id: <1435825251-674-2-git-send-email-pbonzini@redhat.com> In-Reply-To: <1435825251-674-1-git-send-email-pbonzini@redhat.com> References: <1435825251-674-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH 1/9] main-loop: use qemu_mutex_lock_iothread consistently List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: famz@redhat.com, Frederic Konrad The next patch will require the BQL to be always taken with qemu_mutex_lock_iothread(), while right now this isn't the case. Outside TCG mode this is not a problem. In TCG mode, we need to be careful and avoid the "prod out of compiled code" step if already in a VCPU thread. This is easily done with a check on current_cpu, i.e. qemu_in_vcpu_thread(). Hopefully, multithreaded TCG will get rid of the whole logic to kick VCPUs whenever an I/O event occurs! Cc: Frederic Konrad Signed-off-by: Paolo Bonzini --- cpus.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/cpus.c b/cpus.c index 4f0e54d..c09fbef 100644 --- a/cpus.c +++ b/cpus.c @@ -954,7 +954,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg) CPUState *cpu = arg; int r; - qemu_mutex_lock(&qemu_global_mutex); + qemu_mutex_lock_iothread(); qemu_thread_get_self(cpu->thread); cpu->thread_id = qemu_get_thread_id(); cpu->can_do_io = 1; @@ -1034,10 +1034,10 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) { CPUState *cpu = arg; + qemu_mutex_lock_iothread(); qemu_tcg_init_cpu_signals(); qemu_thread_get_self(cpu->thread); - qemu_mutex_lock(&qemu_global_mutex); CPU_FOREACH(cpu) { cpu->thread_id = qemu_get_thread_id(); cpu->created = true; @@ -1149,7 +1149,11 @@ bool qemu_in_vcpu_thread(void) void qemu_mutex_lock_iothread(void) { atomic_inc(&iothread_requesting_mutex); - if (!tcg_enabled() || !first_cpu || !first_cpu->thread) { + /* In the simple case there is no need to bump the VCPU thread out of + * TCG code execution. + */ + if (!tcg_enabled() || qemu_in_vcpu_thread() || + !first_cpu || !first_cpu->thread) { qemu_mutex_lock(&qemu_global_mutex); atomic_dec(&iothread_requesting_mutex); } else { -- 2.4.3