Re: libports and interrupted RPCs

On 18/09/2025 01:33, Samuel Thibault wrote:
>>        /* Don't remove 'cancel' from the cancellation list otherwise
>> 	 any future calls to this function would add it onto a new
>> 	 cancellation list resulting in pointless additional
>> 	 cancellation. The cancellation list pointers are safely
>> 	 managed when the RPC is completed.*/
> Are they really?
I believe so, yes.
> This seems really fragile pointer manipulation to me, even if it's
> alright now, later developers will possibly get it wrong. I'd be simpler

I don't see why it is more or less fragile than the current_rpcs list 
management. This new code acts quite similarly to the linking/unlinking 
performed by begin_rpc/end_rpc. The cancellation list links are added in 
ports_interrupt_rpcs and removed in end_rpc. If there was a need to 
apply this code change to the other instances of iteration around 
hurd_thread_cancel, then I would factorise this code to provide one 
common cancellation list linking function with the unlinking still 
managed by end_rpc.

The cancellation links have to be managed by end_rpc anyway to support 
the case that the RPC completes before the attempt is made to cancel in 
ports_interrupt_rpcs(). That is the biggest benefit in using the linked 
list rather than a localised array.

> to just remember that it's already canceled, and let end_rpc clear that
> at the same time as it unlinks the rpc_info from the port.

I'm sorry but I don't understand this part. Can you elaborate?

Regards,

Mike.