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Three new Stellux syscalls (SYS_FUTEX_WAIT=1030, SYS_FUTEX_WAKE=1031, SYS_FUTEX_WAKE_ALL=1032) providing the kernel-side foundation for userspace synchronization primitives (mutexes, condvars, barriers). Implementation uses a fixed 256-bucket hash table keyed by (mm_context, uaddr). Waiters are stack-allocated in the syscall handler. Wake batching follows the existing wait_queue.cpp pattern. Timeout support via timer::schedule_sleep, thread kill handled through existing force_wake_for_kill path. Co-authored-by: Albert Slepak <FlareCoding@users.noreply.github.com>
Tests cover: EAGAIN on mismatch, wake with no waiters, basic wait/wake, wake count limiting, timeout, killed thread unblock, wake_all, and address independence. Also fix futex_wait to handle kernel tasks (null mm_ctx) by reading the futex word directly instead of going through uaccess validation. Co-authored-by: Albert Slepak <FlareCoding@users.noreply.github.com>
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Co-authored-by: Albert Slepak <FlareCoding@users.noreply.github.com>
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The timeout test was calling futex_wait directly from the boot/idle task, which cannot block. Moved the wait into a spawned kernel task. Also moved timer::schedule_sleep before the bucket lock release to close a preemption window between TASK_STATE_BLOCKED and timer arm. Co-authored-by: Albert Slepak <FlareCoding@users.noreply.github.com>
1. Move uaccess validation before the bucket spinlock. copy_from_user acquires mm_ctx->lock (sleeping mutex) which must not be held under a spinlock. The value is re-read directly under the lock after the page has been faulted in. 2. Add timer::cancel_sleep after yield to prevent a stale timer from spuriously waking the task during a later unrelated blocking op. Co-authored-by: Albert Slepak <FlareCoding@users.noreply.github.com>
Avoids signed wrap when count > INT32_MAX (e.g. UINT32_MAX) which would make the comparison trivially true after waking just one task. Co-authored-by: Albert Slepak <FlareCoding@users.noreply.github.com>
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