feat: add SYS_FUTEX_WAIT and SYS_FUTEX_WAKE syscalls; revamp desktop application categories

kernel/src/Sched/Scheduler.hpp

@@ -126,6 +126,13 @@ namespace Sched {
         bool joinable = true;       // Sibling thread keeps Terminated state for the joiner
         uint64_t threadArg = 0;     // Argument passed into entryPoint on first dispatch
 
+        // Futex wait state (see FutexWait). futexAddr is the user VA this
+        // thread is parked on, 0 when not in a futex wait. futexSeq orders
+        // waiters so FutexWake releases the longest-waiting first.
+        uint64_t futexAddr = 0;
+        uint64_t futexSeq = 0;
+        bool futexWoken = false;
+
         // I/O redirection for GUI terminal
         bool redirected = false;
         int parentPid = -1;
@@ -270,6 +277,30 @@ namespace Sched {
     // Wake any processes blocked on the given object.
     void WakeObjectWaiters(void* object);
 
+    // ====================================================================
+    // Futexes
+    // ====================================================================
+
+    // Futexes are private to a process: the key is (primary slot, user VA),
+    // so two processes waiting on the same address never see each other.
+    static constexpr uint64_t FutexWaitForever = ~0ULL;
+
+    // Block the current thread on the 32-bit word at `uaddr` if it still
+    // holds `expected`. The comparison and the enrollment happen atomically
+    // under the scheduler lock, so a FutexWake issued after the waker changed
+    // the word can never be lost. `timeoutNs` is rounded up to the 1 ms tick;
+    // FutexWaitForever waits without a deadline, 0 only performs the check.
+    // Returns Success when woken by FutexWake, WouldBlock when the word did
+    // not hold `expected`, TimedOut when the deadline passed, InvalidArgument
+    // for a misaligned address, BadPointer when the word is not mapped.
+    // Spurious Success returns are not possible, but callers must still
+    // re-check their condition: another thread may have run in between.
+    int FutexWait(uint64_t uaddr, uint32_t expected, uint64_t timeoutNs);
+
+    // Wake up to `count` threads of the current process blocked on `uaddr`,
+    // longest-waiting first. Returns the number woken.
+    int FutexWake(uint64_t uaddr, uint32_t count);
+
     // Kill a process by PID. If the process is running on another CPU,
     // sets a kill-pending flag checked on the next timer tick.
     // Returns 0 on success, -1 on failure.