@reb It is a masterpiece. Although it's very much 'of its time' the central premise is still very relevant (and still deeply disturbing)

(And, to answer your other question, no, there is no central Civil Defence planning any more in the UK as far as I'm aware - and I was involved on the periphery of disaster planning & roleplay on behalf of my local NHS until about 15 years ago)

#threads

This redesign of #poser (for #swad) to offer a "multi-reactor" (with multiple #threads running each their own event loop) starts to give me severe headaches.

There is *still* a very rare data #race in the #lockfree #queue. I *think* I can spot it in the pseudo code from the paper I used[1], see screenshot. Have a look at lines E7 and E8. Suppose the thread executing this is suspended after E7 for a "very long time". Now, some dequeue operation from some other thread will eventually dequeue whatever "Q->Tail" was pointing to, and then free it after consumption. Our poor thread resumes, checks the pointer already read in E6 for NULL successfully, and then tries a CAS on tail->next in E9, which is unfortunately inside an object that doesn't exist any more .... If the CAS succeeds because at this memory location happens to be "zero" bytes, we corrupted some random other object that might now reside there. 🤯

Please tell me whether I have an error in my thinking here. Can it be ....? 🤔

Meanwhile, after fixing and improving lots of things, I checked the alternative implementation using #mutexes again, and surprise: Although it's still a bit slower, the difference is now very very small. And it has the clear advantage that it never crashes. 🙈 I'm seriously considering to drop all the lock-free #atomics stuff again and just go with mutexes.

[1] https://dl.acm.org/doi/10.1145/248052.248106

Alt...

Pseudo-code of a lockfree enqueue operation

Last Week in the #ATmosphere:

- 20 million accounts on #Bluesky
- #Threads is taking the competition with Bluesky serious; Bluesky might be closer in size to Threads than thought
- experiments with visualising the firehose
- and a ton of links

Read at: https://fediversereport.com/last-week-in-the-atmosphere-2411-c/

The answer is: 1 (doesn’t count though because he’s a threads tech engineer).

The answer is: 1 (doesn’t count though because he’s a threads tech engineer).

An important distinction is slowly being uncovered about the definition of the term "fediverse." Who is it that gets to decide what this place is? How are we being represented? These are not easy questions to answer and if we don't do a better job describing ourselves, then the job will get done for us by people who don't understand the underlying values we hold. #fediverse #meta #threads

Alt...

An info graphic with two icons, one is the symbol for the fediverse that has risen from below and the other is made by Threads The "open fediverse" symbol The peoples representation of the fediverse The "Corporate Fediverse" symbol Threads* representation of the fediverse *Threads is a sub-brand of Meta as is Instagram, Facebook and WhatsApp