Re: [gtk-vnc-devel] PATCH: Fix co-routine shutdown / release

[Anthony Liguori <anthony codemonkey ws>]

Daniel P. Berrange wrote:
> When the co-routine shuts down we never call coroutine_release, so its
> stack never gets unmapped. We also don't restore the 'current' pointer
> to be the system coroutine. So if you later start a 2nd coroutine we're
> switching state making the return state point to a now deleted coroutine.
> All this makes the whole system very crash happy.
>
> So this patch does a couple of things:
>
>   - When the coroutine exits we call coroutine_release
>   - When the coroutine exits we make the current context point to the
>     system context
>   - Ensures errors from swapcontext are passed back correctly, rather
>     than return zero which indicates success.
>
> With this patch in place, I can now successfully connect to a VNC server,
> disconnect, and then re-connect again without megadeath.
>   

Nice catch!

Regards,

Anthony Liguori

> Dan.
>   
> ------------------------------------------------------------------------
>
> diff -r 7d6bc4441dc1 src/continuation.c
> --- a/src/continuation.c	Fri Jul 06 14:39:12 2007 -0400
> +++ b/src/continuation.c	Fri Jul 06 17:35:48 2007 -0400
> @@ -43,9 +43,7 @@ int cc_swap(struct continuation *from, s
>  	else if (to->exited == 1)
>  		return 1;
>  
> -	swapcontext(&from->uc, &to->uc);
> -
> -	return 0;
> +	return swapcontext(&from->uc, &to->uc);
>  }
>  /*
>   * Local variables:
> diff -r 7d6bc4441dc1 src/coroutine.c
> --- a/src/coroutine.c	Fri Jul 06 14:39:12 2007 -0400
> +++ b/src/coroutine.c	Fri Jul 06 17:37:21 2007 -0400
> @@ -66,7 +66,7 @@ static struct coroutine *current;
>  
>  struct coroutine *coroutine_self(void)
>  {
> -	if (current == 0)
> +	if (current == NULL)
>  		current = &system;
>  	return current;
>  }
> @@ -82,11 +82,13 @@ void *coroutine_swap(struct coroutine *f
>  	if (ret == 0)
>  		return from->data;
>  	else if (ret == 1) {
> +		coroutine_release(to);
> +		current = &system;
>  		to->exited = 1;
>  		return to->data;
>  	}
>  
> -	return 0;
> +	return NULL;
>  }
>  
>  void *yieldto(struct coroutine *to, void *arg)
>   
> ------------------------------------------------------------------------
>
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