[PATCH v2] debugobjects: add a new Kconfig for POOL_SIZE

[Qian Cai]

The current value of ODEBUG_POOL_SIZE is not big enough for systems with
large number of CPUs with timer or/and workqueue objects because during
the early boot, timer objects needs the size equals to

No. CPUs x 2 (worker pool)

start_kernel
  workqueue_init_early
    init_worker_pool
      init_timer_key
        debug_object_init

puls, No. CPUs (if have the hrtimer option)

start_kernel
  sched_init
    hrtick_rq_init
      hrtimer_init
        debug_object_init

Then, workqueue objects requires even more,

No. CPUs x 6 (workqueue)

start_kernel
  workqueue_init_early
    alloc_workqueue
      __alloc_workqueue_key
        alloc_and_link_pwqs
          init_pwq
            debug_object_init

plus, No, CPUs x 2 (worker pool) (if have the perf option)

start_kernel
  perf_event_init
    __init_srcu_struct
      init_srcu_struct_fields
        __init_work
          debug_object_init

As the results, systems have 60+ CPUs with both timer and workqueue
objects enabled could trigger "ODEBUG: Out of memory. ODEBUG disabled".

Hence, add a new Kconfig option so users could adjust ODEBUG_POOL_SIZE
accordingly if either timer or workqueue objects are selected.

Signed-off-by: Qian Cai <cai@xxxxxx>
---

Changes since v1:
* Fixed a few typos.
* Added missing call stacks.
* Removed implementation details from the Kconfig help.

 lib/Kconfig.debug  | 11 +++++++++++
 lib/debugobjects.c |  4 ++++
 2 files changed, 15 insertions(+)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1af29b8224fd..0749dc627eb5 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -449,6 +449,17 @@ config DEBUG_OBJECTS
 	  kernel to track the life time of various objects and validate
 	  the operations on those objects.
 
+config DEBUG_OBJECTS_POOL_SIZE
+	int "Debug objects pool size"
+	depends on DEBUG_OBJECTS_TIMERS || DEBUG_OBJECTS_WORK
+	default 1024
+	help
+	  Some debug objects are allocated during the early boot. Enabling some
+	  options below like timers or workqueue objects may increase the size
+	  required significantly with large number of CPUs. If the kernel
+	  reports "ODEBUG: Out of memory. ODEBUG disabled", please increase
+	  this value.
+
 config DEBUG_OBJECTS_SELFTEST
 	bool "Debug objects selftest"
 	depends on DEBUG_OBJECTS
diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 70935ed91125..b0e8e90f6ad1 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -23,7 +23,11 @@
 #define ODEBUG_HASH_BITS	14
 #define ODEBUG_HASH_SIZE	(1 << ODEBUG_HASH_BITS)
 
+#ifdef CONFIG_DEBUG_OBJECTS_POOL_SIZE
+#define ODEBUG_POOL_SIZE	CONFIG_DEBUG_OBJECTS_POOL_SIZE
+#else
 #define ODEBUG_POOL_SIZE	1024
+#endif
 #define ODEBUG_POOL_MIN_LEVEL	256
 
 #define ODEBUG_CHUNK_SHIFT	PAGE_SHIFT
-- 
2.17.2 (Apple Git-113)