From 60c381e25163bad5395ae51f50723d9b1f039b17 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 1 May 2023 17:42:06 +0200
Subject: [PATCH 172/184] debugobject: Ensure pool refill (again)

The recent fix to ensure atomicity of lookup and allocation inadvertently
broke the pool refill mechanism.

Prior to that change debug_objects_activate() and debug_objecs_assert_init()
invoked debug_objecs_init() to set up the tracking object for statically
initialized objects. That's not longer the case and debug_objecs_init() is
now the only place which does pool refills.

Depending on the number of statically initialized objects this can be
enough to actually deplete the pool, which was observed by Ido via a
debugobjects OOM warning.

Restore the old behaviour by adding explicit refill opportunities to
debug_objects_activate() and debug_objecs_assert_init().

Fixes: 63a759694eed ("debugobject: Prevent init race with static objects")
Reported-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Ido Schimmel <idosch@nvidia.com>
Link: https://lore.kernel.org/r/871qk05a9d.ffs@tglx

(cherry picked from commit 0af462f19e635ad522f28981238334620881badc)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>
---
 lib/debugobjects.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 81b319d574176..a0e8e1b69d99d 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -600,19 +600,24 @@ static struct debug_obj *lookup_object_or_alloc(void *addr, struct debug_bucket
 	return NULL;
 }
 
-static void
-__debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack)
+static void debug_objects_fill_pool(void)
 {
-	struct debug_obj *obj, o;
-	struct debug_bucket *db;
-	unsigned long flags;
-
 	/*
 	 * On RT enabled kernels the pool refill must happen in preemptible
 	 * context:
 	 */
 	if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible())
 		fill_pool();
+}
+
+static void
+__debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack)
+{
+	struct debug_obj *obj, o;
+	struct debug_bucket *db;
+	unsigned long flags;
+
+	debug_objects_fill_pool();
 
 	db = get_bucket((unsigned long) addr);
 
@@ -689,6 +694,8 @@ int debug_object_activate(void *addr, const struct debug_obj_descr *descr)
 	if (!debug_objects_enabled)
 		return 0;
 
+	debug_objects_fill_pool();
+
 	db = get_bucket((unsigned long) addr);
 
 	raw_spin_lock_irqsave(&db->lock, flags);
@@ -884,6 +891,8 @@ void debug_object_assert_init(void *addr, const struct debug_obj_descr *descr)
 	if (!debug_objects_enabled)
 		return;
 
+	debug_objects_fill_pool();
+
 	db = get_bucket((unsigned long) addr);
 
 	raw_spin_lock_irqsave(&db->lock, flags);
-- 
2.55.0

