Re: [Boost-users] Boost intrusive list volatile hook

I am fully aware that volatile is not sufficient when dealing with interrupts and this specific problem. That is not the question. The question is this: *Can I qualify the list hook with volatile and still use the boost intrusive list?* I realize that I can modify or write my own intrusive list. I would prefer to keep in step with boost if possible. On Sun, Nov 25, 2018 at 10:56 PM Stian Zeljko Vrba wrote:

Interrupts are like threads, except worse because you have also reentrancy issues (e.g., can IRQ A happen while the handler for IRQ A is still running, possibly outside of IRQ context). Volatile is not sufficient for several reasons, not the least because insertion/removal into a linked list is not an atomic operation. As I see it you have two choices:

1. Introduce fine-grained locking of list nodes by customizing boost.intrusive (you have to be careful because it’s easy to end up in a deadlock due to reentrancy issues – unless you have some constraints, like IRQ levels, that can prevent this.) 2. Use a lock-free list

You should read about how operating systems (Windows, Linux) tackle these issues.

*From:* Boost-users *On Behalf Of *nat ersoz via Boost-users *Sent:* Sunday, November 25, 2018 18:38 *To:* boost-users@lists.boost.org *Cc:* nat ersoz *Subject:* [Boost-users] Boost intrusive list volatile hook

I intend to use the boost intrusive list to implement an observer pattern.

- The list will cross interrupt boundaries; meaning one interrupt will produce the notifications and the other interrupt will observer the notifications.

- The observer, in response to a notification, might detach itself from the list using the the hook's unlink() function.

- I think that I will need the hook to be declared volatile in order to accommodate this.

I have a minimal code sample here: https://github.com/natersoz/patterns/blob/master/observer/intrusive_list_mem...

My list hook member declaration:

using list_hook_type = boost::intrusive::list_member_hook<

boost::intrusive::link_modeboost::intrusive::auto_unlink

>;

list_hook_type hook;

My list declaration:

using list_type =

boost::intrusive::*list*<

Observer<NotificationType>,

boost::intrusive::constant_time_size<false>,

boost::intrusive::member_hook<

Observer<NotificationType>,

typename Observer<NotificationType>::list_hook_type,

&Observer<NotificationType>::hook>

>;

If I a the volatile keyword to the list hood type, I cannot figure out how to get the list_type declaration to fit into the list template list.

Is it possible?

Thank you.

--

Nat Ersoz 425-417-5182 (cell)

-- Nat Ersoz 425-417-5182 (cell)