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| 2025-01-31 22:02:30 +0100 | CoolMa7 | (~CoolMa7@ip5f5b8957.dynamic.kabel-deutschland.de) CoolMa7 |
| 2025-01-31 22:02:02 +0100 | <dminuoso> | euouae: Like I said, the machinery was not build for loop detection but for preventing concurrent evaluation of the same thunk between two haskell threads. |
| 2025-01-31 22:01:53 +0100 | kimiamania8 | (~65804703@user/kimiamania) kimiamania |
| 2025-01-31 22:01:35 +0100 | <mauke> | only in this case it's more like "if you encounter yourself on the road, kill the current thread" |
| 2025-01-31 22:01:29 +0100 | kimiamania8 | (~65804703@user/kimiamania) (Quit: PegeLinux) |
| 2025-01-31 22:01:18 +0100 | <dminuoso> | But dont ever rely on it firing. |
| 2025-01-31 22:01:16 +0100 | <mauke> | if you encounter the buddha on the road, kill him |
| 2025-01-31 22:01:09 +0100 | <dminuoso> | If it triggers, there's definitely an infinite loop and you can celebrate. :) |
| 2025-01-31 22:00:43 +0100 | <euouae> | well eah, that's good, heuristics can misfire |
| 2025-01-31 22:00:09 +0100 | <dminuoso> | Its not even a heuristic. |
| 2025-01-31 22:00:08 +0100 | <euouae> | right |
| 2025-01-31 22:00:00 +0100 | <dminuoso> | euouae: Like I said: It can only detect a particular kind of infinite loop. |
| 2025-01-31 21:59:23 +0100 | <euouae> | so maybe it's not reliable, just a heuristic? |
| 2025-01-31 21:59:14 +0100 | <euouae> | yeah I was thinking that <<loop>> detection seems roughly like the halting prolbem |
| 2025-01-31 21:58:17 +0100 | <dminuoso> | See https://gitlab.haskell.org/ghc/ghc/-/wikis/commentary/rts/storage/heap-objects#black-holes for some details on blackhole |
| 2025-01-31 21:58:16 +0100 | sarna | (~sarna@d224-221.icpnet.pl) sarna |
| 2025-01-31 21:57:48 +0100 | <dminuoso> | euouae: Note, that every object has a pointer to an info table, and that info table contains entry code. Evaluation is driven by just jumping into that entry code |
| 2025-01-31 21:57:29 +0100 | sarna | (~sarna@d224-221.icpnet.pl) (Ping timeout: 260 seconds) |
| 2025-01-31 21:56:29 +0100 | <dminuoso> | euouae: Start with the `Heap Objects` section |
| 2025-01-31 21:56:11 +0100 | <dminuoso> | Is a good website to remember. |
| 2025-01-31 21:56:05 +0100 | <dminuoso> | euouae: https://gitlab.haskell.org/ghc/ghc/-/wikis/commentary/rts/storage/heap-objects |
| 2025-01-31 21:53:53 +0100 | <ash3en> | i mean the haskell library: https://hackage.haskell.org/package/jack-0.7.2.2/docs/Sound-JACK-MIDI.html |
| 2025-01-31 21:53:39 +0100 | <ash3en> | using jack midi with haskell: do i have to manage memory or something? |
| 2025-01-31 21:53:08 +0100 | <dminuoso> | It was recognized we could use the same machinery to detect some forms of infinite loops |
| 2025-01-31 21:52:42 +0100 | <dminuoso> | mauke: Yes. Its really just a kind of mutual exclusion lock for thunks. |
| 2025-01-31 21:52:24 +0100 | <dminuoso> | You can think of it as some kind of mutual exclusion lock, but with special logic to detect if the entry code recursed into itself. |
| 2025-01-31 21:51:58 +0100 | <euouae> | oh mauke's example relates to black holes? I'll read the whole convo then |
| 2025-01-31 21:51:48 +0100 | <dminuoso> | If not, it will set that mark. |
| 2025-01-31 21:51:39 +0100 | <dminuoso> | Now that entry code both checks for a particular mark BLACKHOLE to be set, if its set, you get a <<loop>> assuming this happened from within the same haskell thread. |
| 2025-01-31 21:51:15 +0100 | <euouae> | interestingly `let x = head [x] in x` just hangs in ghci |
| 2025-01-31 21:50:41 +0100 | <dminuoso> | euouae: and you demand that value by just jmp'ing into that memory region. |
| 2025-01-31 21:50:25 +0100 | <dminuoso> | euouae: So roughly, if you have `let x = <expensive> in ..` then we can think of x being represented in memory as some memory region with a bunch of code |
| 2025-01-31 21:49:53 +0100 | <euouae> | sorry I'm reading from the top so I'm trying to catch up on what was said |
| 2025-01-31 21:49:44 +0100 | <euouae> | mauke, is <<loop>> possible because of sharing? |
| 2025-01-31 21:49:12 +0100 | <dminuoso> | Even in single threaded RTS you will have concurrency. |
| 2025-01-31 21:49:09 +0100 | <mauke> | ah, right |
| 2025-01-31 21:48:34 +0100 | <dminuoso> | While the other use of threads if about haskell threads. |
| 2025-01-31 21:48:24 +0100 | <dminuoso> | Note that "threaded RTS" talks about OS threads |
| 2025-01-31 21:48:08 +0100 | <dminuoso> | mauke: Im not sure how the threaded RTS changes, but blackholing should be needed for single threaded RTS too. |
| 2025-01-31 21:46:05 +0100 | <dminuoso> | So consider it a bonus *if* it triggers. |
| 2025-01-31 21:46:00 +0100 | <mauke> | i.e. in multi-thread mode a thread could re-enter the thunk and end up waiting for itself (deadlock) |
| 2025-01-31 21:45:54 +0100 | <dminuoso> | (And it does not work reliably either for a bunch of reasons) |
| 2025-01-31 21:45:44 +0100 | dsrt^ | (~dsrt@108.192.66.114) (Ping timeout: 252 seconds) |
| 2025-01-31 21:45:23 +0100 | <dminuoso> | The <<loop>> is just some opportunistic debugging helper, its not the core feature. |
| 2025-01-31 21:45:18 +0100 | <mauke> | did they change that? I have a vague memory that <<loop>> detection didn't work in multi-thread mode |
| 2025-01-31 21:45:04 +0100 | <dminuoso> | So it gets woken up whenever the thunk finished. |
| 2025-01-31 21:44:48 +0100 | <dminuoso> | If another thread enters a blackhole, it gets put on a list to be woken up later. |
| 2025-01-31 21:44:33 +0100 | <dminuoso> | mauke: If the same thread enters a blackhole, that blackhole acts as loop detection., |
| 2025-01-31 21:44:25 +0100 | <dminuoso> | mauke: Okay, so there's two behaviors to blackhole. |
| 2025-01-31 21:44:08 +0100 | alexherbo2 | (~alexherbo@2a02-8440-3503-94e0-1866-04f2-f81a-c1ec.rev.sfr.net) (Remote host closed the connection) |