From 54f22c83d8f649f5c34d1b4d89050e00c631a32e Mon Sep 17 00:00:00 2001
From: Farid Zakaria <fmzakari@meta.com>
Date: Mon, 6 Jul 2026 11:03:42 -0700
Subject: [PATCH] Initialize TSD tcache before enabling it

---
 src/tcache.c    | 14 +++++++++-----
 src/tsd.c       |  4 +---
 test/unit/tsd.c | 29 +++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/src/tcache.c b/src/tcache.c
index 87a44522..9e442cc8 100644
--- a/src/tcache.c
+++ b/src/tcache.c
@@ -1044,24 +1044,28 @@ tcache_create_explicit(tsd_t *tsd) {
 bool
 tsd_tcache_enabled_data_init(tsd_t *tsd) {
 	/* Called upon tsd initialization. */
-	tsd_tcache_enabled_set(tsd, opt_tcache);
 	/*
 	 * tcache is not available yet, but we need to set up its tcache_nbins
 	 * in advance.
 	 */
 	tcache_default_settings_init(tsd_tcache_slowp_get(tsd));
-	tsd_slow_update(tsd);
+
+#if defined(JEMALLOC_JET) || defined(JEMALLOC_UNIT_TEST)
 	if (test_hooks_tsd_bootstrap_hook != NULL) {
 		test_hooks_tsd_bootstrap_hook();
 	}
+#endif
 
+	bool err = false;
 	if (opt_tcache) {
-		/* Trigger tcache init. */
-		return tsd_tcache_data_init(
+		/* Initialize the bins before advertising the tcache. */
+		err = tsd_tcache_data_init(
 			tsd, NULL, tcache_get_default_ncached_max());
 	}
 
-	return false;
+	tsd_tcache_enabled_set(tsd, opt_tcache && !err);
+	tsd_slow_update(tsd);
+	return err;
 }
 
 void
diff --git a/src/tsd.c b/src/tsd.c
index ff023a21..9c05e17f 100644
--- a/src/tsd.c
+++ b/src/tsd.c
@@ -182,9 +182,7 @@ tsd_fetch_slow(tsd_t *tsd, bool minimal) {
 				tsd_slow_update(tsd);
 				/* Trigger cleanup handler registration. */
 				tsd_set(tsd);
-				tsd_pre_reentrancy_raw(tsd);
 				tsd_data_init(tsd);
-				tsd_post_reentrancy_raw(tsd);
 			}
 		} else {
 			tsd_state_set(tsd, tsd_state_minimal_initialized);
@@ -212,9 +210,9 @@ tsd_fetch_slow(tsd_t *tsd, bool minimal) {
 			/* Switch to fully initialized. */
 			tsd_state_set(tsd, tsd_state_nominal);
 			assert(*tsd_reentrancy_levelp_get(tsd) >= 1);
+			(*tsd_reentrancy_levelp_get(tsd))--;
 			tsd_slow_update(tsd);
 			tsd_data_init(tsd);
-			tsd_post_reentrancy_raw(tsd);
 		} else {
 			assert_tsd_data_cleanup_done(tsd);
 		}
diff --git a/test/unit/tsd.c b/test/unit/tsd.c
index 7dee910b..1e291133 100644
--- a/test/unit/tsd.c
+++ b/test/unit/tsd.c
@@ -131,10 +131,12 @@ TEST_BEGIN(test_tsd_reincarnation) {
 TEST_END
 
 static bool tsd_bootstrap_reentrant_hook_ran;
+static unsigned tsd_bootstrap_reentrant_hook_runs;
 
 static void
 tsd_bootstrap_reentrant_hook(void) {
 	tsd_bootstrap_reentrant_hook_ran = true;
+	tsd_bootstrap_reentrant_hook_runs++;
 	test_hooks_tsd_bootstrap_hook = NULL;
 
 	void *p = malloc(16);
@@ -157,12 +159,39 @@ thd_start_reentrant_tsd_bootstrap(void *arg) {
 	return NULL;
 }
 
+static void *
+thd_start_reentrant_tsd_bootstrap_minimal(void *arg) {
+	(void)arg;
+
+	tsd_t *tsd = tsd_fetch_min();
+	expect_u_eq(tsd_state_get(tsd), tsd_state_minimal_initialized,
+	    "TSD should be minimal initialized");
+
+	test_hooks_tsd_bootstrap_hook = tsd_bootstrap_reentrant_hook;
+	void *p = malloc(1);
+	expect_ptr_not_null(p, "Unexpected malloc() failure");
+	free(p);
+	test_hooks_tsd_bootstrap_hook = NULL;
+
+	expect_true(tsd_bootstrap_reentrant_hook_ran,
+	    "TSD bootstrap hook should have executed");
+	return NULL;
+}
+
 TEST_BEGIN(test_tsd_reentrant_bootstrap) {
 	thd_t thd;
 
 	tsd_bootstrap_reentrant_hook_ran = false;
+	tsd_bootstrap_reentrant_hook_runs = 0;
 	thd_create(&thd, thd_start_reentrant_tsd_bootstrap, NULL);
 	thd_join(thd, NULL);
+
+	tsd_bootstrap_reentrant_hook_ran = false;
+	thd_create(&thd, thd_start_reentrant_tsd_bootstrap_minimal, NULL);
+	thd_join(thd, NULL);
+
+	expect_u_eq(tsd_bootstrap_reentrant_hook_runs, 2,
+	    "TSD bootstrap hook should have executed once per case");
 }
 TEST_END