From b722e5cb3d3eac1093021f8bda85d362ee8eaa1d Mon Sep 17 00:00:00 2001
From: Rongsong Shen <rshen@shenrs.eu>
Date: Thu, 30 Apr 2026 06:04:21 +0000
Subject: [PATCH] feat: add sel_alloc_thread_id ownership check in eval_select
 and gc_sweep (6-10)

---
 src/include/resreq.h            |  5 +++++
 src/lib/testsuite/test_select.c | 29 +++++++++++++++++++++++++++++
 src/lib/xce_select.c            | 16 ++++++++++++++++
 src/scheduler/src/main.c        |  9 +++++++++
 4 files changed, 59 insertions(+)

diff --git a/src/include/resreq.h b/src/include/resreq.h
index 380e53e..39c7787 100644
--- a/src/include/resreq.h
+++ b/src/include/resreq.h
@@ -96,6 +96,11 @@ extern xce_select_node_t* makeSelectNode(sel_node_type_t type,
 extern void sel_optimize_set(int level);
 extern int  sel_get_optimize_level(void);
 
+/* Register the calling thread as the sole allocator/eval/GC thread.
+ * Must be called once at scheduler startup (before eval_select or
+ * gc_sweep_select_nodes).  When unregistered (id==0) the checks are skipped. */
+extern void sel_register_alloc_thread(void);
+
 /* Intern table lifecycle */
 extern void sel_node_table_init(void);
 extern void sel_node_table_fini(void);
diff --git a/src/lib/testsuite/test_select.c b/src/lib/testsuite/test_select.c
index 736fc43..cfd475f 100644
--- a/src/lib/testsuite/test_select.c
+++ b/src/lib/testsuite/test_select.c
@@ -2226,6 +2226,32 @@ test_gc_clear_marks_exported(void)
     sel_optimize_test_reset();
 }
 
+/* ── Task 8: sel_alloc_thread_id ownership check ─────────────────────────*/
+
+static void
+test_sel_register_alloc_thread(void)
+{
+    sel_optimize_test_reset();   /* resets sel_alloc_thread_id to 0 */
+    sel_optimize_set(1);
+    sel_node_table_init();
+
+    /* Should not crash when unregistered (id=0 means skip check) */
+    xce_select_node_t* n = makeSelectNode(SEL_TRUE, 0, 0);
+    TEST_ASSERT_NOT_NULL(n);
+
+    /* Register current thread */
+    sel_register_alloc_thread();
+
+    /* makeSelectNode from same thread must still work */
+    xce_select_node_t* n2 = makeSelectNode(SEL_FALSE, 0, 0);
+    TEST_ASSERT_NOT_NULL(n2);
+
+    gc_clear_marks();
+    gc_sweep_select_nodes(NULL, 0);
+    sel_node_table_fini();
+    sel_optimize_test_reset();
+}
+
 /* ── Top-level runner ─────────────────────────────────────────────────────*/
 
 void
@@ -2337,5 +2363,8 @@ test_select(void)
     /* ── Phase 6 prep: exported GC mark primitives ───────────────────── */
     RUN_TEST(test_gc_clear_marks_exported);
 
+    /* ── Task 8: sel_alloc_thread_id ownership check ─────────────────── */
+    RUN_TEST(test_sel_register_alloc_thread);
+
     xstring_table_fini();
 }
diff --git a/src/lib/xce_select.c b/src/lib/xce_select.c
index 2166a87..3c9920a 100644
--- a/src/lib/xce_select.c
+++ b/src/lib/xce_select.c
@@ -7,6 +7,7 @@
 #define UNIT_TEST 1   /* expose sel_optimize_test_reset in resreq.h */
 
 #include <errno.h>
+#include <pthread.h>
 #include <stdatomic.h>
 #include <stdint.h>
 #include <stdlib.h>
@@ -23,6 +24,7 @@
 /* ── optimize level ───────────────────────────────────────────────────── */
 
 static _Atomic int g_sel_optimize_level = -1;   /* -1 = unset */
+static pthread_t   sel_alloc_thread_id;          /* 0 = unregistered — skip checks */
 
 void sel_optimize_set(int level)
 {
@@ -184,6 +186,12 @@ void sel_optimize_test_reset(void)
 {
     sel_node_table_fini();
     atomic_store_explicit(&g_sel_optimize_level, -1, memory_order_seq_cst);
+    sel_alloc_thread_id = 0;
+}
+
+void sel_register_alloc_thread(void)
+{
+    sel_alloc_thread_id = pthread_self();
 }
 
 /* ── node construction ───────────────────────────────────────────────── */
@@ -643,6 +651,10 @@ int eval_select(const xce_select_node_t* node, select_eval_ctx_t* ctx)
     if (sel_get_optimize_level() <= 0) {
         ERROR("eval_select called with optimize_level <= 0"); abort();
     }
+    if (sel_alloc_thread_id != 0 && !pthread_equal(pthread_self(), sel_alloc_thread_id)) {
+        ERROR("eval_select called from non-allocator thread");
+        return -1;
+    }
 
     /* bitmap cache hit */
     if (node->node_id < ctx->bool_bits_cap) {
@@ -863,6 +875,10 @@ void gc_sweep_select_nodes(const xce_sched_job_t** live_jobs, size_t njobs)
     if (sel_node_table.table == NULL) {
         return;
     }
+    if (sel_alloc_thread_id != 0 && !pthread_equal(pthread_self(), sel_alloc_thread_id)) {
+        ERROR("gc_sweep_select_nodes called from non-allocator thread");
+        return;
+    }
 
     int caps = sel_node_table.nodes.caps;
 
diff --git a/src/scheduler/src/main.c b/src/scheduler/src/main.c
index 2e9bbfc..5cdd30e 100644
--- a/src/scheduler/src/main.c
+++ b/src/scheduler/src/main.c
@@ -10,6 +10,7 @@
 
 #include "scheduler.h"
 
+#include "resreq.h"
 #include "utils.h"
 
 extern int scheduler_req_handler(xce_request_t*, void*);
@@ -118,6 +119,14 @@ int main(int argc, char* argv[])
 
     while (1) {
         sched_update(&sched);
+
+        /* Register this thread as the sole eval/GC allocator thread (write-once) */
+        static int sel_thread_registered = 0;
+        if (!sel_thread_registered) {
+            sel_register_alloc_thread();
+            sel_thread_registered = 1;
+        }
+
         sched_begin_session(&sched);
         sched_go(&sched);