Re: [Qemu-devel] [RFC PATCH] convert ram_list to RCU DQ

[Paolo Bonzini]

Il 28/08/2013 18:02, Mike Day ha scritto:
> @@ -1102,15 +1110,15 @@ void qemu_ram_set_idstr(ram_addr_t addr, const char 
> *name, DeviceState *dev)
>      pstrcat(new_block->idstr, sizeof(new_block->idstr), name);
>  
>      /* This assumes the iothread lock is taken here too.  */
> -    qemu_mutex_lock_ramlist();
> -    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
> +    rcu_read_lock();
> +    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
>          if (block != new_block && !strcmp(block->idstr, new_block->idstr)) {
>              fprintf(stderr, "RAMBlock \"%s\" already registered, abort!\n",
>                      new_block->idstr);
>              abort();
>          }
>      }
> -    qemu_mutex_unlock_ramlist();
> +    rcu_read_unlock();

Forgot about this.  Every time you see "This assumes the iothread lock
is taken here too", you're in the write side so you do not need
lock/unlock and you do not need...

>      /* This assumes the iothread lock is taken here too.  */
>      qemu_mutex_lock_ramlist();
> -    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
> +    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
>          if (addr == block->offset) {
> -            QTAILQ_REMOVE(&ram_list.blocks, block, next);
> +            QLIST_REMOVE_RCU(block, next);
>              ram_list.mru_block = NULL;
>              ram_list.version++;
>              g_free(block);

qemu_mutex_lock_ramlist/qemu_mutex_unlock_ramlist either.

Otherwise, the patch is pretty solid!  Thanks,

Paolo