Re: [Qemu-devel] [PATCH v6 71/73] cpus-common: release BQL earlier in run_on_cpu

[Alex Bennée]

Emilio G. Cota <address@hidden> writes:

> After completing the conversion to per-CPU locks, there is no need
> to release the BQL after having called cpu_kick.
>
> Reviewed-by: Richard Henderson <address@hidden>
> Signed-off-by: Emilio G. Cota <address@hidden>

Reviewed-by: Alex Bennée <address@hidden>

> ---
>  cpus-common.c | 20 +++++---------------
>  1 file changed, 5 insertions(+), 15 deletions(-)
>
> diff --git a/cpus-common.c b/cpus-common.c
> index 62e282bff1..1241024b2c 100644
> --- a/cpus-common.c
> +++ b/cpus-common.c
> @@ -145,6 +145,11 @@ void run_on_cpu(CPUState *cpu, run_on_cpu_func func, 
> run_on_cpu_data data)
>          return;
>      }
>
> +    /* We are going to sleep on the CPU lock, so release the BQL */
> +    if (has_bql) {
> +        qemu_mutex_unlock_iothread();
> +    }
> +
>      wi.func = func;
>      wi.data = data;
>      wi.done = false;
> @@ -153,21 +158,6 @@ void run_on_cpu(CPUState *cpu, run_on_cpu_func func, 
> run_on_cpu_data data)
>
>      cpu_mutex_lock(cpu);
>      queue_work_on_cpu_locked(cpu, &wi);
> -
> -    /*
> -     * We are going to sleep on the CPU lock, so release the BQL.
> -     *
> -     * During the transition to per-CPU locks, we release the BQL _after_
> -     * having kicked the destination CPU (from queue_work_on_cpu_locked 
> above).
> -     * This makes sure that the enqueued work will be seen by the CPU
> -     * after being woken up from the kick, since the CPU sleeps on the BQL.
> -     * Once we complete the transition to per-CPU locks, we will release
> -     * the BQL earlier in this function.
> -     */
> -    if (has_bql) {
> -        qemu_mutex_unlock_iothread();
> -    }
> -
>      while (!atomic_mb_read(&wi.done)) {
>          CPUState *self_cpu = current_cpu;


--
Alex Bennée