feat: continue work on sched

src/sched.c

@@ -575,31 +575,77 @@ uint32 threadCreateUser(const char* name, uint64 entry, uint64 userStackTop)
     return slot;
 }
 
+/* CFS-lite selection: every reschedule rebuilds a min-vruntime priority
+   queue (prioq.h, backed by the intrusive rbt) from every currently
+   Runnable thread and picks the minimum. The queue is deliberately
+   ephemeral (built fresh each call, discarded after one pop) rather than a
+   run-queue whose membership persists across calls -- a thread can become
+   Runnable from code paths other than schedule() itself (schedWakeChannel,
+   called from pipe.c on the producer/consumer side of a wait-queue), and
+   rebuilding from the authoritative `state` field every time means there is
+   never a second copy of "who is runnable" to fall out of sync. */
 uint64 schedule(uint64 currentRsp)
 {
     if (!schedulerActive)
         return currentRsp;
 
-    threads[currentIndex].rsp = currentRsp;
-    if (threads[currentIndex].state == threadRunning)
-        threads[currentIndex].state = threadRunnable;
+    Thread* current = &threads[currentIndex];
+    current->rsp = currentRsp;
+    if (current->state == threadRunning) {
+        current->vruntime += schedTickCharge * schedDefaultWeight / current->weight;
+        current->state = threadRunnable;
+    }
 
     uint64 now = pitTicks();
     for (uint32 i = 0; i < threadTotal; i++)
         if (threads[i].state == threadSleeping && now >= threads[i].sleepUntil)
             threads[i].state = threadRunnable;
 
-    uint32 next = 0;
-    for (uint32 step = 1; step <= threadTotal; step++) {
-        uint32 candidate = (currentIndex + step) % threadTotal;
-        if (threads[candidate].state == threadRunnable) {
-            next = candidate;
-            break;
-        }
+    /* sysPoll's own timeout, forced the exact same way sleepUntil's expiry
+       is above: a thread parked on schedPollChannel because none of its
+       requested fds were ready yet still needs to wake up on its own even
+       if NONE of them ever becomes ready (pollDeadline == 0 means "wait
+       forever", i.e. a real timeout of -1, and is deliberately never
+       forced here). The retried sysPoll call (syscall.c) re-checks every
+       fd from scratch on wake regardless of why it woke, so forcing
+       Runnable here without clearing waitChannel first (same as the
+       sleepUntil scan just above) is enough -- there is no separate
+       "why did I wake" state to reconcile. */
+    for (uint32 i = 0; i < threadTotal; i++)
+        if (threads[i].state == threadBlocked && threads[i].pollActive &&
+            threads[i].pollDeadline != 0 && now >= threads[i].pollDeadline)
+            threads[i].state = threadRunnable;
+
+    /* Real alarm(2) delivery: a deadline set by threadSetAlarm fires here,
+       once per timer tick, regardless of what state its owning thread is
+       currently in (Running, Sleeping, Blocked -- a real alarm keeps
+       ticking no matter what the process is doing). Cleared BEFORE
+       raising, not after, so one expiry fires sigAlrm exactly once, not
+       once per tick until something else clears it; sigRaiseInfo (signal.h)
+       already refuses a Dead/Unused target harmlessly, so a thread that
+       exited with an alarm still pending needs no special case here.
+       siCodeKernel/0/0: a real SIGALRM has no sending process and no exit
+       status of its own to report (real Unix's own SIGALRM si_code is
+       SI_KERNEL/SI_TIMER for exactly this reason -- it is the kernel's
+       timer, not another process, that raised it). */
+    for (uint32 i = 0; i < threadTotal; i++)
+        if (threads[i].alarmAt != 0 && now >= threads[i].alarmAt) {
+            threads[i].alarmAt = 0;
+            sigRaiseInfo(threads[i].id, sigAlrm, siCodeKernel, 0, 0);
         }
 
+    PrioQueue ready;
+    prioqInit(&ready);
+    for (uint32 i = 0; i < threadTotal; i++)
+        if (threads[i].state == threadRunnable)
+            prioqInsert(&ready, &threads[i].schedNode, threads[i].vruntime, threads[i].id);
+
+    PrioQNode* winner = prioqPopMin(&ready);
+    uint32 next = winner ? winner->id : currentIndex;
+
     currentIndex = next;
     threads[next].state = threadRunning;
+    threads[next].everRan = true;
     tssSetRsp0(threads[next].kernelStackTop);
     return threads[next].rsp;
 }
@@ -615,6 +661,7 @@ void schedStart(void)
 void threadExit(uint64 code)
 {
     Thread* thread = &threads[currentIndex];
+    thread->exitCode = code;
     thread->state = threadDead;
     kprintf("[user] pid=%u '%s' exited with code %lu\n", thread->id, thread->name, code);
 }