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)
