On 11/08/2016 17:24, Alex Bennée wrote:
> Once TCG gains the ability to sleep individual threads we need to make
> sure they don't sleep when safe work is pending as all threads need to
> go through the process_queued_work function. Also if we have multiple
> threads wait_for_safe_work can now sleep without deadlocking.
>
> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
>
> ---
> v4
> - new for v4, ontop of async-safe-work-v5
> ---
> cpu-exec-common.c | 15 ++++++++++++++-
> cpus.c | 2 +-
> include/qom/cpu.h | 8 ++++++++
> 3 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/cpu-exec-common.c b/cpu-exec-common.c
> index e29cf6d..84cb789 100644
> --- a/cpu-exec-common.c
> +++ b/cpu-exec-common.c
> @@ -83,6 +83,18 @@ QemuCond qemu_exclusive_cond;
>
> static int safe_work_pending;
>
> +/* No vCPUs can sleep while there is safe work pending as we need
> + * everything to finish up in process_cpu_work.
> + */
> +bool cpu_has_queued_work(CPUState *cpu)
> +{
> + if (cpu->queued_work || atomic_mb_read(&safe_work_pending) > 0) {
> + return true;
> + } else {
> + return false;
> + }
> +}
This should not be needed anymore with the new version. If a safe work
item is pending, its CPU will have cpu->queued_work != NULL. The work
item will then run as soon as the CPU is scheduled because no other CPUs
can be inside TCG.
Paolo
> #ifdef CONFIG_USER_ONLY
> #define can_wait_for_safe() (1)
> #else
> @@ -91,7 +103,8 @@ static int safe_work_pending;
> * all vCPUs are in the same thread. This will change for MTTCG
> * however.
> */
> -#define can_wait_for_safe() (0)
> +extern int smp_cpus;
> +#define can_wait_for_safe() (mttcg_enabled && smp_cpus > 1)
> #endif
>
> void wait_safe_cpu_work(void)
> diff --git a/cpus.c b/cpus.c
> index 8a40a08..4fc5e4c 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -88,7 +88,7 @@ bool cpu_is_stopped(CPUState *cpu)
>
> static bool cpu_thread_is_idle(CPUState *cpu)
> {
> - if (cpu->stop || cpu->queued_work) {
> + if (cpu->stop || cpu_has_queued_work(cpu)) {
> return false;
> }
> if (cpu_is_stopped(cpu)) {
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 5ecbd29..d0db846 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -661,6 +661,14 @@ void async_run_on_cpu(CPUState *cpu, run_on_cpu_func
> func, void *data);
> void async_safe_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data);
>
> /**
> + * cpu_has_queued_work:
> + * @cpu: The vCPU to check
> + *
> + * Returns true if there is *_run_on_cpu work to be done.
> + */
> +bool cpu_has_queued_work(CPUState *cpu);
> +
> +/**
> * qemu_get_cpu:
> * @index: The CPUState@cpu_index value of the CPU to obtain.
> *
>
