Commit a8efa606 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

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: default avatarEmilio G. Cota <cota@braap.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent d98f2607

cpus.c

+8 −4
Original line number Diff line number Diff line
@@ -1220,17 +1220,21 @@ 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();



    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();

    }