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Subject[RFC V2] kthread: add object debug support
Date
From: Qianli Zhao <zhaoqianli@xiaomi.com>

Add debugobject support to track the life time of kthread_work
which is used to detect reinitialization/free active object problems
Add kthread_init_work_onstack/kthread_init_delayed_work_onstack for
kthread onstack support

Signed-off-by: Qianli Zhao <zhaoqianli@xiaomi.com>
---
I got an crash issue since kthread_delayed_work reinitialization,crash log show us that is a timer NULL pointer exception
[16238.089921] Unable to handle kernel paging request at virtual address dead000000000208
[16238.090298] Call trace:
[16238.090307] run_timer_softirq+0x2d0/0xa30
[16238.090318] __do_softirq+0x1dc/0x384
[16238.090328] irq_exit+0xb4/0xb8
[16238.090338] __handle_domain_irq+0x84/0xc0
[16238.090345] gic_handle_irq+0x138/0x1bc
[16238.090353] el1_irq+0xb0/0x128
[16238.090362] queue_work_on+0x54/0x60
[16238.090374] _process_event_group+0x190/0x230
[16238.090382] kgsl_process_event_groups+0x44/0x70
[16238.090391] adreno_dispatcher_work+0x1e4/0xae8
[16238.090400] kthread_worker_fn+0xec/0x180
[16238.090407] kthread+0x118/0x128
[16238.090415] ret_from_fork+0x10/0x18

It turns out that the problem is caused by the timer reinitialization,after enable CONFIG_DEBUG_OBJECTS_TIMERS,the reason for the problem is obvious.

This timer belongs to kthread_delayed_work,from kernel log we also see list corruption WARNING:
[30858.395766] list_del corruption. next->prev should be ffffffe388ebbf88, but was ffffffe388ebb588
[30858.395788] WARNING: CPU: 2 PID: 387 at /home/work/data/miui_codes/build_home/kernel/msm-4.19/lib/list_debug.c:56 __list_del_entry_valid+0xc8/0xd0
...
[30858.405951] list_add corruption. next->prev should be prev (ffffffe389392620), but was ffffffe388ebbf88. (next=ffffffe388ebbf88).
[30858.405977] WARNING: CPU: 0 PID: 7721 at /home/work/data/miui_codes/build_home/kernel/msm-4.19/lib/list_debug.c:25 __list_add_valid+0x7c/0xc8

crash> struct kthread_worker.delayed_work_list 0xffffffe3893925f0
[ffffffe389392620] delayed_work_list = {
next = 0xffffffe388ebbf88,
prev = 0xffffffe388ebb588
}
crash> list 0xffffffe388ebbf88
ffffffe388ebbf88

delayed_work_list is corruption,this work is reinitialized.if kthread_work reinitialized after move to work_list,this work will be carried out forever in kthread_worker_fn.

Timer and workqueue both provide debugobject support,kthread_work similar with workqueue,so i think it is necessary to support objectdebug in kthread_work.

---
include/linux/kthread.h | 29 ++++++++++++++-
include/linux/poison.h | 3 ++
kernel/kthread.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++-
lib/Kconfig.debug | 10 ++++++
4 files changed, 135 insertions(+), 2 deletions(-)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 65b81e0..1530953 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -108,6 +108,16 @@ struct kthread_delayed_work {
struct timer_list timer;
};

+#ifdef CONFIG_DEBUG_OBJECTS_KTHREAD
+extern void __init_kwork(struct kthread_work *kwork, int onstack);
+extern void destroy_kwork_on_stack(struct kthread_work *kwork);
+extern void destroy_delayed_kwork_on_stack(struct kthread_delayed_work *kdwork);
+#else
+static inline void __init_kwork(struct kthread_work *kwork, int onstack) { }
+static inline void destroy_kwork_on_stack(struct kthread_work *kwork) { }
+static inline void destroy_delayed_kwork_on_stack(struct kthread_delayed_work *kdwork) { }
+#endif
+
#define KTHREAD_WORKER_INIT(worker) { \
.lock = __RAW_SPIN_LOCK_UNLOCKED((worker).lock), \
.work_list = LIST_HEAD_INIT((worker).work_list), \
@@ -115,7 +125,7 @@ struct kthread_delayed_work {
}

#define KTHREAD_WORK_INIT(work, fn) { \
- .node = LIST_HEAD_INIT((work).node), \
+ .node = { .next = KWORK_ENTRY_STATIC }, \
.func = (fn), \
}

@@ -160,6 +170,15 @@ extern void __kthread_init_worker(struct kthread_worker *worker,
#define kthread_init_work(work, fn) \
do { \
memset((work), 0, sizeof(struct kthread_work)); \
+ __init_kwork(work, 0); \
+ INIT_LIST_HEAD(&(work)->node); \
+ (work)->func = (fn); \
+ } while (0)
+
+#define kthread_init_work_onstack(work, fn) \
+ do { \
+ memset((work), 0, sizeof(struct kthread_work)); \
+ __init_kwork(work, 1); \
INIT_LIST_HEAD(&(work)->node); \
(work)->func = (fn); \
} while (0)
@@ -172,6 +191,14 @@ extern void __kthread_init_worker(struct kthread_worker *worker,
TIMER_IRQSAFE); \
} while (0)

+#define kthread_init_delayed_work_onstack(dwork, fn) \
+ do { \
+ kthread_init_work_onstack(&(dwork)->work, (fn)); \
+ __init_timer_on_stack(&(dwork)->timer, \
+ kthread_delayed_work_timer_fn, \
+ TIMER_IRQSAFE); \
+ } while (0)
+
int kthread_worker_fn(void *worker_ptr);

__printf(2, 3)
diff --git a/include/linux/poison.h b/include/linux/poison.h
index df34330..2e6a370 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -86,4 +86,7 @@
/********** security/ **********/
#define KEY_DESTROY 0xbd

+/********** kernel/kthread **********/
+#define KWORK_ENTRY_STATIC ((void *) 0x600 + POISON_POINTER_DELTA)
+
#endif
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 132f84a..ca00bd2 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -67,6 +67,94 @@ enum KTHREAD_BITS {
KTHREAD_SHOULD_PARK,
};

+#ifdef CONFIG_DEBUG_OBJECTS_KTHREAD
+static struct debug_obj_descr kwork_debug_descr;
+
+static void *kwork_debug_hint(void *addr)
+{
+ return ((struct kthread_work *) addr)->func;
+}
+
+static bool kwork_is_static_object(void *addr)
+{
+ struct kthread_work *kwork = addr;
+
+ return (kwork->node.prev == NULL &&
+ kwork->node.next == KWORK_ENTRY_STATIC);
+}
+
+static bool kwork_fixup_init(void *addr, enum debug_obj_state state)
+{
+ struct kthread_work *kwork = addr;
+
+ switch (state) {
+ case ODEBUG_STATE_ACTIVE:
+ kthread_cancel_work_sync(kwork);
+ debug_object_init(kwork, &kwork_debug_descr);
+ return true;
+ default:
+ return false;
+ }
+}
+
+static bool kwork_fixup_free(void *addr, enum debug_obj_state state)
+{
+ struct kthread_work *kwork = addr;
+
+ switch (state) {
+ case ODEBUG_STATE_ACTIVE:
+ kthread_cancel_work_sync(kwork);
+ debug_object_free(kwork, &kwork_debug_descr);
+ return true;
+ default:
+ return false;
+ }
+}
+
+static struct debug_obj_descr kwork_debug_descr = {
+ .name = "kthread_work",
+ .debug_hint = kwork_debug_hint,
+ .is_static_object = kwork_is_static_object,
+ .fixup_init = kwork_fixup_init,
+ .fixup_free = kwork_fixup_free,
+};
+
+static inline void debug_kwork_activate(struct kthread_work *kwork)
+{
+ debug_object_activate(kwork, &kwork_debug_descr);
+}
+
+static inline void debug_kwork_deactivate(struct kthread_work *kwork)
+{
+ debug_object_deactivate(kwork, &kwork_debug_descr);
+}
+
+void __init_kwork(struct kthread_work *kwork, int onstack)
+{
+ if (onstack)
+ debug_object_init_on_stack(kwork, &kwork_debug_descr);
+ else
+ debug_object_init(kwork, &kwork_debug_descr);
+}
+EXPORT_SYMBOL_GPL(__init_kwork);
+
+void destroy_kwork_on_stack(struct kthread_work *kwork)
+{
+ debug_object_free(kwork, &kwork_debug_descr);
+}
+EXPORT_SYMBOL_GPL(destroy_kwork_on_stack);
+
+void destroy_delayed_kwork_on_stack(struct kthread_delayed_work *kdwork)
+{
+ destroy_timer_on_stack(&kdwork->timer);
+ debug_object_free(&kdwork->work, &kwork_debug_descr);
+}
+EXPORT_SYMBOL_GPL(destroy_delayed_kwork_on_stack);
+#else
+static inline void debug_kwork_activate(struct kthread_work *kwork) { }
+static inline void debug_kwork_deactivate(struct kthread_work *kwork) { }
+#endif
+
static inline void set_kthread_struct(void *kthread)
{
/*
@@ -698,6 +786,7 @@ int kthread_worker_fn(void *worker_ptr)
work = list_first_entry(&worker->work_list,
struct kthread_work, node);
list_del_init(&work->node);
+ debug_kwork_deactivate(work);
}
worker->current_work = work;
raw_spin_unlock_irq(&worker->lock);
@@ -835,8 +924,11 @@ static void kthread_insert_work(struct kthread_worker *worker,

list_add_tail(&work->node, pos);
work->worker = worker;
- if (!worker->current_work && likely(worker->task))
+
+ if (!worker->current_work && likely(worker->task)) {
+ debug_kwork_activate(work);
wake_up_process(worker->task);
+ }
}

/**
@@ -1054,6 +1146,7 @@ static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
*/
if (!list_empty(&work->node)) {
list_del_init(&work->node);
+ debug_kwork_deactivate(work);
return true;
}

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9ad9210..8355984 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -540,6 +540,16 @@ config DEBUG_OBJECTS_WORK
work queue routines to track the life time of work objects and
validate the work operations.

+config DEBUG_OBJECTS_KTHREAD
+ bool "Debug kthread work objects"
+ depends on DEBUG_OBJECTS
+ help
+ If you say Y here, additional code will be inserted into the
+ kthread routines to track the life time of kthread objects and
+ validate the kthread operations.
+
+ If unsure, say N.
+
config DEBUG_OBJECTS_RCU_HEAD
bool "Debug RCU callbacks objects"
depends on DEBUG_OBJECTS
--
2.7.4
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