From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44761) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gMtaY-0001pW-8g for qemu-devel@nongnu.org; Wed, 14 Nov 2018 06:44:06 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gMtaV-00038C-5e for qemu-devel@nongnu.org; Wed, 14 Nov 2018 06:44:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51958) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gMtaV-00037y-0z for qemu-devel@nongnu.org; Wed, 14 Nov 2018 06:44:03 -0500 From: Paolo Bonzini Date: Wed, 14 Nov 2018 12:44:00 +0100 Message-Id: <20181114114400.15577-1-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH] cpus: run work items for all vCPUs if single-threaded List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: dgilbert@redhat.com, alex.bennee@linaro.org, cota@braap.org This avoids the following deadlock: 1) a thread calls run_on_cpu for CPU 2 from a timer, and single_tcg_halt_cond is signaled 2) CPU 1 is running and exits. It finds no work item and enters CPU 2 3) because the I/O thread is stuck in run_on_cpu, the round-robin kick timer never triggers, and CPU 2 never runs the work item 4) run_on_cpu never completes Signed-off-by: Paolo Bonzini --- cpus.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/cpus.c b/cpus.c index a2b33ccb29..0ddeeefc14 100644 --- a/cpus.c +++ b/cpus.c @@ -1220,16 +1220,20 @@ static void qemu_wait_io_event_common(CPUState *cpu) process_queued_cpu_work(cpu); } -static void qemu_tcg_rr_wait_io_event(CPUState *cpu) +static void qemu_tcg_rr_wait_io_event(void) { + CPUState *cpu; + while (all_cpu_threads_idle()) { stop_tcg_kick_timer(); - qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex); + qemu_cond_wait(first_cpu->halt_cond, &qemu_global_mutex); } start_tcg_kick_timer(); - qemu_wait_io_event_common(cpu); + CPU_FOREACH(cpu) { + qemu_wait_io_event_common(cpu); + } } static void qemu_wait_io_event(CPUState *cpu) @@ -1562,7 +1566,7 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg) qemu_notify_event(); } - qemu_tcg_rr_wait_io_event(cpu ? cpu : first_cpu); + qemu_tcg_rr_wait_io_event(); deal_with_unplugged_cpus(); } -- 2.17.1