Re: [Qemu-devel] [RFC 23/38] cpu-exec: grab iothread lock during interrupt handling

[Paolo Bonzini]

On 24/08/2015 02:23, Emilio G. Cota wrote:
> Signed-off-by: Emilio G. Cota <address@hidden>
> ---
>  cpu-exec.c        | 34 ++++++++++++++++++++++++++++------
>  include/qom/cpu.h |  1 +
>  2 files changed, 29 insertions(+), 6 deletions(-)
> 
> diff --git a/cpu-exec.c b/cpu-exec.c
> index fd57b9c..a1700ac 100644
> --- a/cpu-exec.c
> +++ b/cpu-exec.c
> @@ -371,6 +371,29 @@ 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();
> +    }

This can use qemu_mutex_iothread_locked, avoiding the introduction of a
new CPUState member.

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)
> @@ -452,12 +475,8 @@ 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. */
>                          interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK;
> @@ -503,6 +522,8 @@ int cpu_exec(CPUState *cpu)
>                             the program flow was changed */
>                          next_tb = 0;
>                      }
> +
> +                    cpu_exit_loop_lock_reset(cpu);
>                  }
>                  if (unlikely(cpu->exit_request)) {
>                      cpu->exception_index = EXCP_INTERRUPT;
> @@ -609,6 +630,7 @@ int cpu_exec(CPUState *cpu)
>              env = &x86_cpu->env;
>  #endif
>              tb_lock_reset();
> +            cpu_exit_loop_lock_reset(cpu);
>          }
>      } /* for(;;) */
>  
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 1d97b63..dbe0438 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -270,6 +270,7 @@ struct CPUState {
>      bool created;
>      bool stop;
>      bool stopped;
> +    bool cpu_loop_exit_locked;
>      volatile sig_atomic_t exit_request;
>      uint32_t interrupt_request;
>      int singlestep_enabled;
>