runtime: rewrite channel implementation #4556
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Size difference with the dev branch: Binary size differenceflash ram before after diff before after diff 287104 286624 -480 -0.17% 18212 18212 0 0.00% tinygo build -size short -o ./build/test.hex -target=wioterminal -stack-size 8kb ./examples/net/mqttclient/paho/ 119312 118864 -448 -0.38% 7848 7848 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 -stack-size 8kb ./examples/net/tcpclient/ 111516 111068 -448 -0.40% 7772 7772 0 0.00% tinygo build -size short -o ./build/test.hex -target=arduino-mkrwifi1010 -stack-size 8kb ./examples/net/tlsclient/ 13720 13304 -416 -3.03% 4940 4940 0 0.00% tinygo build -size short -o ./build/test.hex -target=nucleo-wl55jc ./examples/sx126x/lora_rxtx/ 83056 82640 -416 -0.50% 6588 6588 0 0.00% tinygo build -size short -o ./build/test.hex -target=nucleo-wl55jc ./examples/lora/lorawan/atcmd/ 245468 245052 -416 -0.17% 10488 10488 0 0.00% tinygo build -size short -o ./build/test.hex -target=nano-rp2040 -stack-size 8kb 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./examples/net/ntpclient/ 5267020 5262188 -4832 -0.00% 786474 786490 16 0.00% |
This rewrite simplifies the channel implementation considerably, with 34% less LOC. Perhaps the most important change is the removal of the channel state, which made sense when we had only send and receive operations but only makes things more compliated when multiple select operations can be pending on a single channel. I did this rewrite originally to make it possible to make channels parallelism-safe. The current implementation is not parallelism-safe, but it will be easy to make it so (the main additions will be a channel lock, a global select lock, and an atomic compare-and-swap in chanQueue.pop).
eliasnaur
reviewed
Nov 9, 2024
Comment on lines
+64
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| chanOperationWaiting = iota // waiting for a send/receive operation to continue | ||
| chanOperationOk // successfully sent or received (not closed) | ||
| chanOperationClosed // channel was closed, the value has been zeroed |
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Nit: because of chanOperationMask, these would be clearer (to me) spelled out in binary literal form.
| // Pop the next waiting channel from the queue. Channels that are no longer | ||
| // waiting (for example, when they're part of a select operation) will be | ||
| // skipped. | ||
| // This function must be called with interrupts disabled. |
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Is 'interrupts disabled' still accurate when our lord and saviour, multithreading support, arrives? Here and below.
| ch.blocked = blockedlist | ||
| chanDebug(ch) | ||
| interrupt.Restore(i) | ||
| // We can't proceed, so we add ourselfs to the list of receivers and wait |
|
@aykevl any responses to @eliasnaur comments? 😸 |
|
Also note that I changed the branch for the PR just now to |
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This rewrite simplifies the channel implementation considerably, with 34% fewer LOC. Perhaps the most important change is the removal of the channel state, which made sense when we had only send and receive operations but only makes things more compliated when multiple select operations can be pending on a single channel.
I did this rewrite originally to make it possible to make channels parallelism-safe (see #2446). The current implementation is not parallelism-safe, but it will be easy to make it so (the main additions will be a channel lock, a global select lock, and an atomic compare-and-swap in chanQueue.pop).
This change also reduces binary size: for the driver examples that do change (presumably the ones that use a channel), the code size is reduced by around 400 bytes.