Re: [PATCH 3/3] softmmu: Remove cpu_reloading_memory_map as unused

[Alex Bennée]

Richard Henderson <richard.henderson@linaro.org> writes:

> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

This is just cleanup, I think it should be merged with 2/3

> ---
>  include/exec/cpu-common.h   |  1 -
>  accel/tcg/cpu-exec-common.c | 30 ------------------------------
>  2 files changed, 31 deletions(-)
>
> diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
> index 87dc9a752c..41788c0bdd 100644
> --- a/include/exec/cpu-common.h
> +++ b/include/exec/cpu-common.h
> @@ -133,7 +133,6 @@ static inline void cpu_physical_memory_write(hwaddr addr,
>  {
>      cpu_physical_memory_rw(addr, (void *)buf, len, true);
>  }
> -void cpu_reloading_memory_map(void);
>  void *cpu_physical_memory_map(hwaddr addr,
>                                hwaddr *plen,
>                                bool is_write);
> diff --git a/accel/tcg/cpu-exec-common.c b/accel/tcg/cpu-exec-common.c
> index 9a5fabf625..7e35d7f4b5 100644
> --- a/accel/tcg/cpu-exec-common.c
> +++ b/accel/tcg/cpu-exec-common.c
> @@ -33,36 +33,6 @@ void cpu_loop_exit_noexc(CPUState *cpu)
>      cpu_loop_exit(cpu);
>  }
>  
> -#if defined(CONFIG_SOFTMMU)
> -void cpu_reloading_memory_map(void)
> -{
> -    if (qemu_in_vcpu_thread() && current_cpu->running) {
> -        /* The guest can in theory prolong the RCU critical section as long
> -         * as it feels like. The major problem with this is that because it
> -         * can do multiple reconfigurations of the memory map within the
> -         * critical section, we could potentially accumulate an unbounded
> -         * collection of memory data structures awaiting reclamation.
> -         *
> -         * Because the only thing we're currently protecting with RCU is the
> -         * memory data structures, it's sufficient to break the critical 
> section
> -         * in this callback, which we know will get called every time the
> -         * memory map is rearranged.
> -         *
> -         * (If we add anything else in the system that uses RCU to protect
> -         * its data structures, we will need to implement some other 
> mechanism
> -         * to force TCG CPUs to exit the critical section, at which point 
> this
> -         * part of this callback might become unnecessary.)
> -         *
> -         * This pair matches cpu_exec's rcu_read_lock()/rcu_read_unlock(), 
> which
> -         * only protects cpu->as->dispatch. Since we know our caller is about
> -         * to reload it, it's safe to split the critical section.
> -         */
> -        rcu_read_unlock();
> -        rcu_read_lock();
> -    }
> -}
> -#endif
> -
>  void cpu_loop_exit(CPUState *cpu)
>  {
>      /* Undo the setting in cpu_tb_exec.  */


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro