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Subject[RFC/PATCH 3/3] debugobjects: Use static keys for debug_objects_enabled
Date
Instead of using a __read_mostly variable for returning early
from debug_objects operations use static keys. This should
allow us to dynamically patch out debug_objects code from a
running kernel and reduce the overhead of having debug objects
compiled in and not enabled.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
The inlining is sort of ugly.

include/linux/debugobjects.h | 94 +++++++++++++++++++++++++++++++++++++-----
lib/debugobjects.c | 73 ++++++++++++--------------------
2 files changed, 110 insertions(+), 57 deletions(-)
diff --git a/include/linux/debugobjects.h b/include/linux/debugobjects.h
index 0e5f578..902e430 100644
--- a/include/linux/debugobjects.h
+++ b/include/linux/debugobjects.h
@@ -3,6 +3,7 @@

#include <linux/list.h>
#include <linux/spinlock.h>
+#include <linux/jump_label.h>

enum debug_obj_state {
ODEBUG_STATE_NONE,
@@ -60,26 +61,94 @@ struct debug_obj_descr {
};

#ifdef CONFIG_DEBUG_OBJECTS
-extern void debug_object_init (void *addr, struct debug_obj_descr *descr);
+extern struct static_key debug_objects_enabled;
+#if CONFIG_DEBUG_OBJECTS_ENABLE_DEFAULT == 1
+ #define debug_object_branch static_key_true
+#else
+ #define debug_object_branch static_key_false
+#endif
+
+extern void _debug_object_init(void *addr, struct debug_obj_descr *descr);
+static __always_inline void
+debug_object_init(void *addr, struct debug_obj_descr *descr)
+{
+ if (debug_object_branch(&debug_objects_enabled))
+ _debug_object_init(addr, descr);
+}
+
extern void
-debug_object_init_on_stack(void *addr, struct debug_obj_descr *descr);
-extern void debug_object_activate (void *addr, struct debug_obj_descr *descr);
-extern void debug_object_deactivate(void *addr, struct debug_obj_descr *descr);
-extern void debug_object_destroy (void *addr, struct debug_obj_descr *descr);
-extern void debug_object_free (void *addr, struct debug_obj_descr *descr);
-extern void debug_object_assert_init(void *addr, struct debug_obj_descr *descr);
+_debug_object_init_on_stack(void *addr, struct debug_obj_descr *descr);
+static __always_inline void
+debug_object_init_on_stack(void *addr, struct debug_obj_descr *descr)
+{
+ if (debug_object_branch(&debug_objects_enabled))
+ _debug_object_init_on_stack(addr, descr);
+}
+
+extern void _debug_object_activate(void *addr, struct debug_obj_descr *descr);
+static __always_inline void
+debug_object_activate(void *addr, struct debug_obj_descr *descr)
+{
+ if (debug_object_branch(&debug_objects_enabled))
+ _debug_object_activate(addr, descr);
+}
+
+extern void _debug_object_deactivate(void *addr, struct debug_obj_descr *descr);
+static __always_inline void
+debug_object_deactivate(void *addr, struct debug_obj_descr *descr)
+{
+ if (debug_object_branch(&debug_objects_enabled))
+ _debug_object_deactivate(addr, descr);
+}

+extern void _debug_object_destroy(void *addr, struct debug_obj_descr *descr);
+static __always_inline void
+debug_object_destroy(void *addr, struct debug_obj_descr *descr)
+{
+ if (debug_object_branch(&debug_objects_enabled))
+ _debug_object_destroy(addr, descr);
+}
+
+extern void _debug_object_free(void *addr, struct debug_obj_descr *descr);
+static __always_inline void
+debug_object_free(void *addr, struct debug_obj_descr *descr)
+{
+ if (debug_object_branch(&debug_objects_enabled))
+ _debug_object_free(addr, descr);
+}
+
+extern void
+_debug_object_assert_init(void *addr, struct debug_obj_descr *descr);
+static __always_inline void
+debug_object_assert_init(void *addr, struct debug_obj_descr *descr)
+{
+ if (debug_object_branch(&debug_objects_enabled))
+ _debug_object_assert_init(addr, descr);
+}
/*
* Active state:
* - Set at 0 upon initialization.
* - Must return to 0 before deactivation.
*/
extern void
-debug_object_active_state(void *addr, struct debug_obj_descr *descr,
+_debug_object_active_state(void *addr, struct debug_obj_descr *descr,
unsigned int expect, unsigned int next);
+static __always_inline void
+debug_object_active_state(void *addr, struct debug_obj_descr *descr,
+ unsigned int expect, unsigned int next)
+{
+ if (debug_object_branch(&debug_objects_enabled))
+ _debug_object_active_state(addr, descr, expect, next);
+}

extern void debug_objects_early_init(void);
-extern void debug_objects_mem_init(void);
+
+extern void _debug_objects_mem_init(void);
+static __always_inline void debug_objects_mem_init(void)
+{
+ if (debug_object_branch(&debug_objects_enabled))
+ _debug_objects_mem_init();
+}
#else
static inline void
debug_object_init (void *addr, struct debug_obj_descr *descr) { }
@@ -101,7 +170,12 @@ static inline void debug_objects_mem_init(void) { }
#endif

#ifdef CONFIG_DEBUG_OBJECTS_FREE
-extern void debug_check_no_obj_freed(const void *address, unsigned long size);
+extern void _debug_check_no_obj_freed(const void *address, unsigned long size);
+#define debug_check_no_obj_freed(address, size) \
+ ({ \
+ if (debug_object_branch(&debug_objects_enabled)) \
+ _debug_check_no_obj_freed(address, size); \
+ })
#else
static inline void
debug_check_no_obj_freed(const void *address, unsigned long size) { }
diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 77cb245..4ca24a5 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -14,6 +14,7 @@
#include <linux/debugfs.h>
#include <linux/slab.h>
#include <linux/hash.h>
+#include <linux/static_key.h>

#define ODEBUG_HASH_BITS 14
#define ODEBUG_HASH_SIZE (1 << ODEBUG_HASH_BITS)
@@ -47,8 +48,12 @@ static struct kmem_cache *obj_cache;
static int debug_objects_maxchain __read_mostly;
static int debug_objects_fixups __read_mostly;
static int debug_objects_warnings __read_mostly;
-static int debug_objects_enabled __read_mostly
- = CONFIG_DEBUG_OBJECTS_ENABLE_DEFAULT;
+struct static_key debug_objects_enabled __read_mostly
+#if CONFIG_DEBUG_OBJECTS_ENABLE_DEFAULT == 1
+ = STATIC_KEY_INIT_TRUE;
+#else
+ = STATIC_KEY_INIT_FALSE;
+#endif

static struct debug_obj_descr *descr_test __read_mostly;

@@ -57,13 +62,15 @@ static DECLARE_WORK(debug_obj_work, free_obj_work);

static int __init enable_object_debug(char *str)
{
- debug_objects_enabled = 1;
+ if (!static_key_enabled(&debug_objects_enabled))
+ static_key_slow_inc(&debug_objects_enabled);
return 0;
}

static int __init disable_object_debug(char *str)
{
- debug_objects_enabled = 0;
+ if (static_key_enabled(&debug_objects_enabled))
+ static_key_slow_dec(&debug_objects_enabled);
return 0;
}

@@ -320,7 +327,7 @@ __debug_object_init(void *addr, struct debug_obj_descr *descr, int onstack)
if (!obj) {
obj = alloc_object(addr, db, descr);
if (!obj) {
- debug_objects_enabled = 0;
+ static_key_slow_dec(&debug_objects_enabled);
raw_spin_unlock_irqrestore(&db->lock, flags);
debug_objects_oom();
return;
@@ -357,11 +364,8 @@ __debug_object_init(void *addr, struct debug_obj_descr *descr, int onstack)
* @addr: address of the object
* @descr: pointer to an object specific debug description structure
*/
-void debug_object_init(void *addr, struct debug_obj_descr *descr)
+void _debug_object_init(void *addr, struct debug_obj_descr *descr)
{
- if (!debug_objects_enabled)
- return;
-
__debug_object_init(addr, descr, 0);
}

@@ -371,11 +375,8 @@ void debug_object_init(void *addr, struct debug_obj_descr *descr)
* @addr: address of the object
* @descr: pointer to an object specific debug description structure
*/
-void debug_object_init_on_stack(void *addr, struct debug_obj_descr *descr)
+void _debug_object_init_on_stack(void *addr, struct debug_obj_descr *descr)
{
- if (!debug_objects_enabled)
- return;
-
__debug_object_init(addr, descr, 1);
}

@@ -384,7 +385,7 @@ void debug_object_init_on_stack(void *addr, struct debug_obj_descr *descr)
* @addr: address of the object
* @descr: pointer to an object specific debug description structure
*/
-void debug_object_activate(void *addr, struct debug_obj_descr *descr)
+void _debug_object_activate(void *addr, struct debug_obj_descr *descr)
{
enum debug_obj_state state;
struct debug_bucket *db;
@@ -394,9 +395,6 @@ void debug_object_activate(void *addr, struct debug_obj_descr *descr)
.state = ODEBUG_STATE_NOTAVAILABLE,
.descr = descr };

- if (!debug_objects_enabled)
- return;
-
db = get_bucket((unsigned long) addr);

raw_spin_lock_irqsave(&db->lock, flags);
@@ -442,15 +440,12 @@ void debug_object_activate(void *addr, struct debug_obj_descr *descr)
* @addr: address of the object
* @descr: pointer to an object specific debug description structure
*/
-void debug_object_deactivate(void *addr, struct debug_obj_descr *descr)
+void _debug_object_deactivate(void *addr, struct debug_obj_descr *descr)
{
struct debug_bucket *db;
struct debug_obj *obj;
unsigned long flags;

- if (!debug_objects_enabled)
- return;
-
db = get_bucket((unsigned long) addr);

raw_spin_lock_irqsave(&db->lock, flags);
@@ -489,16 +484,13 @@ void debug_object_deactivate(void *addr, struct debug_obj_descr *descr)
* @addr: address of the object
* @descr: pointer to an object specific debug description structure
*/
-void debug_object_destroy(void *addr, struct debug_obj_descr *descr)
+void _debug_object_destroy(void *addr, struct debug_obj_descr *descr)
{
enum debug_obj_state state;
struct debug_bucket *db;
struct debug_obj *obj;
unsigned long flags;

- if (!debug_objects_enabled)
- return;
-
db = get_bucket((unsigned long) addr);

raw_spin_lock_irqsave(&db->lock, flags);
@@ -535,16 +527,13 @@ out_unlock:
* @addr: address of the object
* @descr: pointer to an object specific debug description structure
*/
-void debug_object_free(void *addr, struct debug_obj_descr *descr)
+void _debug_object_free(void *addr, struct debug_obj_descr *descr)
{
enum debug_obj_state state;
struct debug_bucket *db;
struct debug_obj *obj;
unsigned long flags;

- if (!debug_objects_enabled)
- return;
-
db = get_bucket((unsigned long) addr);

raw_spin_lock_irqsave(&db->lock, flags);
@@ -575,15 +564,12 @@ out_unlock:
* @addr: address of the object
* @descr: pointer to an object specific debug description structure
*/
-void debug_object_assert_init(void *addr, struct debug_obj_descr *descr)
+void _debug_object_assert_init(void *addr, struct debug_obj_descr *descr)
{
struct debug_bucket *db;
struct debug_obj *obj;
unsigned long flags;

- if (!debug_objects_enabled)
- return;
-
db = get_bucket((unsigned long) addr);

raw_spin_lock_irqsave(&db->lock, flags);
@@ -616,16 +602,13 @@ void debug_object_assert_init(void *addr, struct debug_obj_descr *descr)
* @next: state to move to if expected state is found
*/
void
-debug_object_active_state(void *addr, struct debug_obj_descr *descr,
+_debug_object_active_state(void *addr, struct debug_obj_descr *descr,
unsigned int expect, unsigned int next)
{
struct debug_bucket *db;
struct debug_obj *obj;
unsigned long flags;

- if (!debug_objects_enabled)
- return;
-
db = get_bucket((unsigned long) addr);

raw_spin_lock_irqsave(&db->lock, flags);
@@ -713,10 +696,9 @@ repeat:
}
}

-void debug_check_no_obj_freed(const void *address, unsigned long size)
+void _debug_check_no_obj_freed(const void *address, unsigned long size)
{
- if (debug_objects_enabled)
- __debug_check_no_obj_freed(address, size);
+ __debug_check_no_obj_freed(address, size);
}
#endif

@@ -750,7 +732,7 @@ static int __init debug_objects_init_debugfs(void)
{
struct dentry *dbgdir, *dbgstats;

- if (!debug_objects_enabled)
+ if (!debug_object_branch(&debug_objects_enabled))
return 0;

dbgdir = debugfs_create_dir("debug_objects", NULL);
@@ -912,7 +894,7 @@ check_results(void *addr, enum debug_obj_state state, int fixups, int warnings)
out:
raw_spin_unlock_irqrestore(&db->lock, flags);
if (res)
- debug_objects_enabled = 0;
+ static_key_slow_dec(&debug_objects_enabled);
return res;
}

@@ -1079,17 +1061,14 @@ free:
* prevents that the debug code is called on kmem_cache_free() for the
* debug tracker objects to avoid recursive calls.
*/
-void __init debug_objects_mem_init(void)
+void __init _debug_objects_mem_init(void)
{
- if (!debug_objects_enabled)
- return;
-
obj_cache = kmem_cache_create("debug_objects_cache",
sizeof (struct debug_obj), 0,
SLAB_DEBUG_OBJECTS, NULL);

if (!obj_cache || debug_objects_replace_static_objects()) {
- debug_objects_enabled = 0;
+ static_key_slow_dec(&debug_objects_enabled);
if (obj_cache)
kmem_cache_destroy(obj_cache);
printk(KERN_WARNING "ODEBUG: out of memory.\n");
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.


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