From a8efa60633575a2ee4dbf807a71cb44d44b0e0f8 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 14 Nov 2018 12:36:57 +0100 Subject: [PATCH] cpus: run work items for all vCPUs if single-threaded This avoids the following I/O thread deadlock: 1) the I/O thread calls run_on_cpu for CPU 3 from a timer. 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 3 never runs the work item 4) run_on_cpu never completes Reviewed-by: Emilio G. Cota 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(); } -- 2.11.4.GIT