Re: [Boost-users] Am I doing something wrong here? Boost threads & intrusive_ptr crash

Subject: Re: [Boost-users] Am I doing something wrong here? Boost threads & intrusive_ptr crash
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2009-06-11 10:19:48

AMDG

Space Ship Traveller wrote:
> <snip>
>
> I'm experiencing a very infrequent crash at the line marked with (*). 
> The note is a reference counted pointer (boost::intrusive_ptr), but by 
> the time we get here, this pointer is invalid, even though there are 
> still references to it in the system. The odd thing is, further up the 
> chain (and on the same thread), I'm checking to ensure that note is 
> valid, i.e.
>
>                 //... display update system, separate thread from 
> event-loop.
>                 ensure(ctx->notificationSource);
>                 loop->postNotification(ctx->notificationSource);
>                 //...
>
> After writing this far in the email, I'm starting to see something 
> where there could be an error. Is it possible that the object 
> reference count is being messed up due to multi-threading issues? I.e. 
> if the object is being passed around on two separate threads, having 
> the reference count incremented and decremented at the same time? 
> Actually, it seems obvious that this could be a problem...
>
> Are there any "patterns" for using reference counted objects across 
> different threads?

shared_ptr's reference count is thread safe.  For intrusive_ptr,
it depends on how you define the reference count.

In Christ,
Steven Watanabe