Re: [Qemu-devel] [RFC PATCH V7 09/19] Drop global lock during TCG code execution

[Paolo Bonzini]

On 10/08/2015 17:27, address@hidden wrote:
>  void qemu_mutex_lock_iothread(void)
>  {
> -    atomic_inc(&iothread_requesting_mutex);
> -    /* In the simple case there is no need to bump the VCPU thread out of
> -     * TCG code execution.
> -     */
> -    if (!tcg_enabled() || qemu_in_vcpu_thread() ||
> -        !first_cpu || !first_cpu->thread) {
> -        qemu_mutex_lock(&qemu_global_mutex);
> -        atomic_dec(&iothread_requesting_mutex);
> -    } else {
> -        if (qemu_mutex_trylock(&qemu_global_mutex)) {
> -            qemu_cpu_kick_thread(first_cpu);
> -            qemu_mutex_lock(&qemu_global_mutex);
> -        }
> -        atomic_dec(&iothread_requesting_mutex);
> -        qemu_cond_broadcast(&qemu_io_proceeded_cond);
> -    }
> -    iothread_locked = true;

"iothread_locked = true" must be kept.  Otherwise... yay! :)

> @@ -125,8 +128,10 @@ void tlb_flush_page(CPUState *cpu, target_ulong addr)
>     can be detected */
>  void tlb_protect_code(ram_addr_t ram_addr)
>  {
> +    qemu_mutex_lock_iothread();
>      cpu_physical_memory_test_and_clear_dirty(ram_addr, TARGET_PAGE_SIZE,
>                                               DIRTY_MEMORY_CODE);
> +    qemu_mutex_unlock_iothread();
>  }
>  

Not needed anymore.

> diff --git a/target-i386/misc_helper.c b/target-i386/misc_helper.c
> index 52c5d65..55f63bf 100644
> --- a/target-i386/misc_helper.c
> +++ b/target-i386/misc_helper.c

None of this is needed anymore either! :)

> +    /*
> +     * Some device's reset needs to grab the global_mutex. So just release it
> +     * here.
> +     */
> +    qemu_mutex_unlock_iothread();
>      /* reset all devices */
>      QTAILQ_FOREACH_SAFE(re, &reset_handlers, entry, nre) {
>          re->func(re->opaque);
>      }
> +    qemu_mutex_lock_iothread();

Should never have been true?  (And, I think, it was pointed out in a
previous version too).

Paolo