Feature/ipc messages and sync - #6
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alexdev8930 merged 4 commits intoOct 3, 2026
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Fills in ipc/ so kernel tasks can pass messages and synchronise. IpcPort is a FIFO of fixed size messages. IpcSend waits while the port is full and IpcReceive waits while it is empty, with Try forms that never wait. A message is copied by value, so neither side holds a pointer into the other's memory. IpcSemaphore counts permits up to a ceiling, and IpcMutex passes ownership straight to the first waiter on unlock so a ready task cannot take the lock ahead of the one that was woken for it. A mutex is not recursive: locking one the caller already holds reports IpcErrOwner instead of parking on a lock nobody else can open. Every entry point returns IpcStatus, so a refused call says why rather than failing silently, and every call checks its arguments before touching memory. IpcPark registers the calling task and sleeps as one step under the interrupt lock. Splitting those two apart would let a waker take the entry, find the task still runnable, and drop the wakeup, leaving the task parked with nobody to wake it. Wait queues are keyed by task id, and a wakeup skips entries whose task was killed, since a dead task can never run again. The idle task cannot sleep, so a call that would have to wait reports IpcErrNoTask rather than parking, matching what timer_sleep_ms does. Adds ipc/ to the VPATH and its objects to KERNEL_OBJS.
Verifies the ipc at boot rather than assuming it works. A producer and a consumer pass 40 messages, which is more than a port holds, so the sender has to park on a full port and the receiver on an empty one, and both have to be woken the right number of times for the counts to line up. The consumer checks each message came back in order and stamped with the sender's id. The mutex test runs two tasks against one lock for as many rounds as they finish before the stop flag, each one checking that the shared counter only ever advanced by one, so the unlock handoff cannot let two tasks into the critical section at once. The semaphore and mutex checks that run in this task also cover the paths that must refuse rather than wait: a re-lock, an unlock from a task that does not hold the lock, a second create on a live port, and a second destroy. The last wait reports IpcErrNoTask, since the idle task has nowhere to park. These run before the shell and worker start, so their output stays on one run of lines instead of landing in the middle of the shell prompt.
Documents the ipc contracts in kernel_api.md now that the headers are implemented, and drops ipc/message.h and ipc/sync.h from the planned interfaces list. The README and the roadmap no longer describe ipc/ as a stub. The version moves to 0.9-dev for the new subsystem. Known issues are listed rather than left for someone to find: none of it is reentrant, a wait queue holds 16 entries and reports IpcErrFull past that, and the objects are static kernel values rather than something a task can allocate.
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Thanks, this is great! I especially like how |
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