Re: [Qemu-devel] [RFC v1 10/11] tcg: grab iothread lock in cpu-exec interrupt handling

[Paolo Bonzini <pbonzini@redhat.com>]

On 18/03/2016 17:18, Alex Bennée wrote:
> From: "Emilio G. Cota" <cota@braap.org>
> 
> Signed-off-by: Emilio G. Cota <cota@braap.org>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> 
> ---
> v1 (ajb)
>  - pulled from emilio/mttcg series
> ---
>  cpu-exec.c        | 33 +++++++++++++++++++++++++++------
>  include/qom/cpu.h |  1 +
>  2 files changed, 28 insertions(+), 6 deletions(-)
> 
> diff --git a/cpu-exec.c b/cpu-exec.c
> index 76891fd..6acaf25 100644
> --- a/cpu-exec.c
> +++ b/cpu-exec.c
> @@ -351,6 +351,29 @@ static void cpu_handle_debug_exception(CPUState *cpu)
>      cc->debug_excp_handler(cpu);
>  }
>  
> +#ifdef CONFIG_SOFTMMU
> +static inline void cpu_exit_loop_lock(CPUState *cpu)
> +{
> +    qemu_mutex_lock_iothread();
> +    cpu->cpu_loop_exit_locked = true;
> +}
> +
> +static inline void cpu_exit_loop_lock_reset(CPUState *cpu)
> +{
> +    if (cpu->cpu_loop_exit_locked) {
> +        cpu->cpu_loop_exit_locked = false;
> +        qemu_mutex_unlock_iothread();
> +    }
> +}

In the meanwhile we got qemu_mutex_iothread_locked(), so these two
inlines are not necessary anymore.

Paolo

> +#else
> +static inline void cpu_exit_loop_lock(CPUState *cpu)
> +{ }
> +
> +static inline void cpu_exit_loop_lock_reset(CPUState *cpu)
> +{ }
> +#endif
> +
>  /* main execution loop */
>  
>  int cpu_exec(CPUState *cpu)
> @@ -450,12 +473,7 @@ int cpu_exec(CPUState *cpu)
>              for(;;) {
>                  interrupt_request = cpu->interrupt_request;
>                  if (unlikely(interrupt_request)) {
> -                    /* FIXME: this needs to take the iothread lock.
> -                     * For this we need to find all places in
> -                     * cc->cpu_exec_interrupt that can call cpu_loop_exit,
> -                     * and call qemu_unlock_iothread_mutex() there.  Else,
> -                     * add a flag telling cpu_loop_exit() to unlock it.
> -                     */
> +                    cpu_exit_loop_lock(cpu);
>  
>                      if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
>                          /* Mask out external interrupts for this step. */
> @@ -510,6 +528,8 @@ int cpu_exec(CPUState *cpu)
>                          next_tb = 0;
>                      }
>  
> +                    cpu_exit_loop_lock_reset(cpu);
> +
>                  }
>                  if (unlikely(cpu->exit_request
>                               || replay_has_interrupt())) {
> @@ -630,6 +650,7 @@ int cpu_exec(CPUState *cpu)
>  
>              cpu->can_do_io = 1;
>              tb_lock_reset();
> +            cpu_exit_loop_lock_reset(cpu);
>          }
>      } /* for(;;) */
>  
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index d6cb7b8..954d97d 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -295,6 +295,7 @@ struct CPUState {
>      bool crash_occurred;
>      bool exit_request;
>      bool tb_invalidated_flag;
> +    bool cpu_loop_exit_locked;
>      uint32_t interrupt_request;
>      int singlestep_enabled;
>      int64_t icount_extra;
>