Hoist semaphore ownership out of TokenExecutor#609
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Move creation and wait-site of the backpressure semaphore from TokenExecutor into its two callers: TaskNotifier (PTY read path) and PTYSession (channel/mux path). TokenExecutor no longer owns any semaphore; it receives one via the semaphore: parameter and passes it through to TokenArray, which signals it on consumption exactly as before. TaskNotifier creates a per-task semaphore on registration and looks it up (under tasksLock) before each read. PTYSession creates one per channel session. No semantic change intended.
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Looks like d518a59 broke the libsixel submodule ref (from e2c8546 to d300081). Don't see the d300081 commit in libsixel fork or upstream. Maybe local changes? |
gnachman
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Mar 12, 2026
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| // Per-task backpressure semaphores, keyed by task identity. | ||
| // Created on register, removed on deregister. | ||
| NSMapTable<id<iTermTask>, dispatch_semaphore_t> *_backpressureSemaphores; |
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What if PTYTask owned its semaphore? Then we wouldn't need _backpressureSemaphores: in fact, TaskNotifier could remain unchanged. -[PTYTask processRead] could wait on and signal its semaphore. Another benefit of doing the wait inside processRead is that it could read before waiting, reducing latency (probably very slightly) when it is eventually unblocked.
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Move creation and wait-site of the backpressure semaphore from TokenExecutor into its callers: TaskNotifier (PTY read path) and PTYSession (channel/mux path).
TokenExecutor no longer owns any semaphore; it receives one via the semaphore: parameter and passes it through to TokenArray, which signals it on consumption exactly as before.
TaskNotifier creates a per-task semaphore on registration and looks it up (under tasksLock) before each read. PTYSession creates one per channel session. No semantic change intended.
As a reminder, this is the first step in flow control abstraction -- no behavioral changes are intended. Next step would be the flow control interface.