[PATCH] kthread: finer-grained lockdep/cross-release completion

[Daniel Vetter <daniel.vetter@ffwll.ch>]

Since -rc1 we're hitting a bunch of lockdep splats using the new
cross-release stuff around the 2 kthread completions. In all cases
they are because totally independent uses of kthread are mixed up by
lockdep into the same locking class, creating artificial deadlocks.

Fix this by converting kthread code in the same way as e.g.
alloc_workqueue already works: Use macros for the public api so we can
have a callsite specific lockdep key, then pass that through the
entire callchain. Due to the many entry points this is slightly
tedious.

Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Marta Lofstedt <marta.lofstedt@intel.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Shaohua Li <shli@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Oleg Nesterov <oleg@redhat.com>
References: https://bugs.freedesktop.org/show_bug.cgi?id=103950
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 include/linux/kthread.h | 48 +++++++++++++++++++++++++++++-----
 kernel/kthread.c        | 68 ++++++++++++++++++++++++++++++++++---------------
 2 files changed, 88 insertions(+), 28 deletions(-)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index c1961761311d..7a9463f0be5c 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -6,10 +6,12 @@
 #include <linux/sched.h>
 #include <linux/cgroup.h>
 
-__printf(4, 5)
-struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
+__printf(6, 7)
+struct task_struct *_kthread_create_on_node(int (*threadfn)(void *data),
 					   void *data,
 					   int node,
+					   struct lock_class_key *exited_key,
+					   struct lock_class_key *parked_key,
 					   const char namefmt[], ...);
 
 /**
@@ -25,12 +27,27 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
  */
 #define kthread_create(threadfn, data, namefmt, arg...) \
 	kthread_create_on_node(threadfn, data, NUMA_NO_NODE, namefmt, ##arg)
+#define kthread_create_on_node(threadfn, data, node, namefmt, arg...)	\
+({									\
+	static struct lock_class_key __exited_key, __parked_key;	\
+	_kthread_create_on_node(threadfn, data, node, &__exited_key,	\
+			       &__parked_key, namefmt, ##arg);		\
+})
 
 
-struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
+struct task_struct *_kthread_create_on_cpu(int (*threadfn)(void *data),
 					  void *data,
 					  unsigned int cpu,
+					  struct lock_class_key *exited_key,
+					  struct lock_class_key *parked_key,
 					  const char *namefmt);
+#define kthread_create_on_cpu(threadfn, data, cpu, namefmt)		\
+({									\
+	static struct lock_class_key __exited_key, __parked_key;	\
+	_kthread_create_on_cpu(threadfn, data, cpu, &__exited_key,\
+			       &__parked_key, namefmt);			\
+})
+
 
 /**
  * kthread_run - create and wake a thread.
@@ -171,13 +188,30 @@ extern void __kthread_init_worker(struct kthread_worker *worker,
 
 int kthread_worker_fn(void *worker_ptr);
 
-__printf(2, 3)
+__printf(4, 5)
 struct kthread_worker *
-kthread_create_worker(unsigned int flags, const char namefmt[], ...);
+_kthread_create_worker(unsigned int flags,
+		       struct lock_class_key *exited_key,
+		       struct lock_class_key *parked_key,
+		       const char namefmt[], ...);
+#define kthread_create_worker(flags, namefmt...)				\
+({									\
+	static struct lock_class_key __exited_key, __parked_key;	\
+	_kthread_create_worker(flags, &__exited_key, &__parked_key,	\
+			       ##namefmt);				\
+})
 
-__printf(3, 4) struct kthread_worker *
-kthread_create_worker_on_cpu(int cpu, unsigned int flags,
+__printf(5, 6) struct kthread_worker *
+_kthread_create_worker_on_cpu(int cpu, unsigned int flags,
+		       struct lock_class_key *exited_key,
+		       struct lock_class_key *parked_key,
 			     const char namefmt[], ...);
+#define kthread_create_worker_on_cpu(cpu, flags, namefmt...)	\
+({									\
+	static struct lock_class_key __exited_key, __parked_key;	\
+	_kthread_create_worker_on_cpu(cpu, flags, &__exited_key, &__parked_key,\
+			       ##namefmt);				\
+})
 
 bool kthread_queue_work(struct kthread_worker *worker,
 			struct kthread_work *work);
diff --git a/kernel/kthread.c b/kernel/kthread.c
index cd50e99202b0..5b73e3da0d2e 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -32,6 +32,7 @@ struct kthread_create_info
 	int (*threadfn)(void *data);
 	void *data;
 	int node;
+	struct lock_class_key *exited_key, *parked_key;
 
 	/* Result passed back to kthread_create() from kthreadd. */
 	struct task_struct *result;
@@ -221,8 +222,15 @@ static int kthread(void *_create)
 	}
 
 	self->data = data;
-	init_completion(&self->exited);
-	init_completion(&self->parked);
+	lockdep_init_map_crosslock(&self->exited.map.map,
+			"(kthread completion)->exited",
+			create->exited_key, 0);
+	init_completion_map(&self->exited, &self->exited.map.map);
+	lockdep_init_map_crosslock(&self->parked.map.map,
+			"(kthread completion)->parked",
+			create->parked_key, 0);
+	init_completion_map(&self->parked, &self->exited.map.map);
+
 	current->vfork_done = &self->exited;
 
 	/* OK, tell user we're spawned, wait for stop or wakeup */
@@ -272,9 +280,11 @@ static void create_kthread(struct kthread_create_info *create)
 	}
 }
 
-static __printf(4, 0)
+static __printf(6, 0)
 struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
 						    void *data, int node,
+						    struct lock_class_key *exited_key,
+						    struct lock_class_key *parked_key,
 						    const char namefmt[],
 						    va_list args)
 {
@@ -289,6 +299,8 @@ struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
 	create->data = data;
 	create->node = node;
 	create->done = &done;
+	create->exited_key = exited_key;
+	create->parked_key = parked_key;
 
 	spin_lock(&kthread_create_lock);
 	list_add_tail(&create->list, &kthread_create_list);
@@ -353,21 +365,24 @@ struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
  *
  * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
  */
-struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
-					   void *data, int node,
-					   const char namefmt[],
-					   ...)
+struct task_struct *_kthread_create_on_node(int (*threadfn)(void *data),
+					    void *data, int node,
+					    struct lock_class_key *exited_key,
+					    struct lock_class_key *parked_key,
+					    const char namefmt[],
+					    ...)
 {
 	struct task_struct *task;
 	va_list args;
 
 	va_start(args, namefmt);
-	task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
+	task = __kthread_create_on_node(threadfn, data, node,
+					exited_key, parked_key, namefmt, args);
 	va_end(args);
 
 	return task;
 }
-EXPORT_SYMBOL(kthread_create_on_node);
+EXPORT_SYMBOL(_kthread_create_on_node);
 
 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
 {
@@ -421,14 +436,16 @@ EXPORT_SYMBOL(kthread_bind);
  * Description: This helper function creates and names a kernel thread
  * The thread will be woken and put into park mode.
  */
-struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
+struct task_struct *_kthread_create_on_cpu(int (*threadfn)(void *data),
 					  void *data, unsigned int cpu,
+					  struct lock_class_key *exited_key,
+					  struct lock_class_key *parked_key,
 					  const char *namefmt)
 {
 	struct task_struct *p;
 
-	p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
-				   cpu);
+	p = _kthread_create_on_node(threadfn, data, cpu_to_node(cpu),
+				    exited_key, parked_key, namefmt, cpu);
 	if (IS_ERR(p))
 		return p;
 	kthread_bind(p, cpu);
@@ -649,8 +666,10 @@ int kthread_worker_fn(void *worker_ptr)
 }
 EXPORT_SYMBOL_GPL(kthread_worker_fn);
 
-static __printf(3, 0) struct kthread_worker *
+static __printf(5, 0) struct kthread_worker *
 __kthread_create_worker(int cpu, unsigned int flags,
+			struct lock_class_key *exited_key,
+			struct lock_class_key *parked_key,
 			const char namefmt[], va_list args)
 {
 	struct kthread_worker *worker;
@@ -666,8 +685,8 @@ __kthread_create_worker(int cpu, unsigned int flags,
 	if (cpu >= 0)
 		node = cpu_to_node(cpu);
 
-	task = __kthread_create_on_node(kthread_worker_fn, worker,
-						node, namefmt, args);
+	task = __kthread_create_on_node(kthread_worker_fn, worker, node,
+					exited_key, parked_key, namefmt, args);
 	if (IS_ERR(task))
 		goto fail_task;
 
@@ -694,18 +713,22 @@ __kthread_create_worker(int cpu, unsigned int flags,
  * when the worker was SIGKILLed.
  */
 struct kthread_worker *
-kthread_create_worker(unsigned int flags, const char namefmt[], ...)
+_kthread_create_worker(unsigned int flags,
+		       struct lock_class_key *exited_key,
+		       struct lock_class_key *parked_key,
+		       const char namefmt[], ...)
 {
 	struct kthread_worker *worker;
 	va_list args;
 
 	va_start(args, namefmt);
-	worker = __kthread_create_worker(-1, flags, namefmt, args);
+	worker = __kthread_create_worker(-1, flags, exited_key, parked_key,
+					 namefmt, args);
 	va_end(args);
 
 	return worker;
 }
-EXPORT_SYMBOL(kthread_create_worker);
+EXPORT_SYMBOL(_kthread_create_worker);
 
 /**
  * kthread_create_worker_on_cpu - create a kthread worker and bind it
@@ -725,19 +748,22 @@ EXPORT_SYMBOL(kthread_create_worker);
  * when the worker was SIGKILLed.
  */
 struct kthread_worker *
-kthread_create_worker_on_cpu(int cpu, unsigned int flags,
+_kthread_create_worker_on_cpu(int cpu, unsigned int flags,
+			      struct lock_class_key *exited_key,
+			      struct lock_class_key *parked_key,
 			     const char namefmt[], ...)
 {
 	struct kthread_worker *worker;
 	va_list args;
 
 	va_start(args, namefmt);
-	worker = __kthread_create_worker(cpu, flags, namefmt, args);
+	worker = __kthread_create_worker(cpu, flags, exited_key, parked_key,
+					 namefmt, args);
 	va_end(args);
 
 	return worker;
 }
-EXPORT_SYMBOL(kthread_create_worker_on_cpu);
+EXPORT_SYMBOL(_kthread_create_worker_on_cpu);
 
 /*
  * Returns true when the work could not be queued at the moment.
-- 
2.15.0