[PATCH v4 10/15] lockdep: Apply crossrelease to completion operation

Byungchul Park
2016-12-09T05:18:12Z

wait_for_completion() and its family can cause deadlock. Nevertheless,
it cannot use the lock correntness validator because complete() will be
called in different context from the context calling
wait_for_completion(), which violates lockdep's assumption without
crossrelease feature.

However, thanks to CONFIG_LOCKDEP_CROSSRELEASE, we can apply the lockdep
detector to wait_for_completion() and complete(). Applied it.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
include/linux/completion.h | 121 +++++++++++++++++++++++++++++++++++++++++----
kernel/locking/lockdep.c | 17 +++++++
kernel/sched/completion.c | 54 +++++++++++---------
lib/Kconfig.debug | 8 +++
4 files changed, 167 insertions(+), 33 deletions(-)

diff --git a/include/linux/completion.h b/include/linux/completion.h
index 5d5aaae..67a27af 100644
--- a/include/linux/completion.h
+++ b/include/linux/completion.h
@@ -9,6 +9,9 @@
*/

#include <linux/wait.h>
+#ifdef CONFIG_LOCKDEP_COMPLETE
+#include <linux/lockdep.h>
+#endif

/*
* struct completion - structure used to maintain state for a "completion"
@@ -25,10 +28,53 @@
struct completion {
unsigned int done;
wait_queue_head_t wait;
+#ifdef CONFIG_LOCKDEP_COMPLETE
+ struct lockdep_map map;
+ struct cross_lock xlock;
+#endif
};

+#ifdef CONFIG_LOCKDEP_COMPLETE
+static inline void complete_acquire(struct completion *x)
+{
+ lock_acquire_exclusive(&x->map, 0, 0, NULL, _RET_IP_);
+}
+
+static inline void complete_release(struct completion *x)
+{
+ lock_release(&x->map, 0, _RET_IP_);
+}
+
+static inline void complete_release_commit(struct completion *x)
+{
+ lock_commit_crosslock(&x->map);
+}
+
+#define init_completion(x) \
+do { \
+ static struct lock_class_key __key; \
+ lockdep_init_map_crosslock(&(x)->map, \
+ &(x)->xlock, \
+ "(complete)" #x, \
+ &__key, 0); \
+ __init_completion(x); \
+} while (0)
+#else
+#define init_completion(x) __init_completion(x)
+static inline void complete_acquire(struct completion *x, int try) {}
+static inline void complete_release(struct completion *x) {}
+static inline void complete_release_commit(struct completion *x) {}
+#endif
+
+#ifdef CONFIG_LOCKDEP_COMPLETE
+#define COMPLETION_INITIALIZER(work) \
+ { 0, __WAIT_QUEUE_HEAD_INITIALIZER((work).wait), \
+ STATIC_CROSS_LOCKDEP_MAP_INIT("(complete)" #work, &(work), \
+ &(work).xlock), STATIC_CROSS_LOCK_INIT()}
+#else
#define COMPLETION_INITIALIZER(work) \
{ 0, __WAIT_QUEUE_HEAD_INITIALIZER((work).wait) }
+#endif

#define COMPLETION_INITIALIZER_ONSTACK(work) \
({ init_completion(&work); work; })
@@ -70,7 +116,7 @@ struct completion {
* This inline function will initialize a dynamically created completion
* structure.
*/
-static inline void init_completion(struct completion *x)
+static inline void __init_completion(struct completion *x)
{
x->done = 0;
init_waitqueue_head(&x->wait);
@@ -88,18 +134,75 @@ static inline void reinit_completion(struct completion *x)
x->done = 0;
}

-extern void wait_for_completion(struct completion *);
-extern void wait_for_completion_io(struct completion *);
-extern int wait_for_completion_interruptible(struct completion *x);
-extern int wait_for_completion_killable(struct completion *x);
-extern unsigned long wait_for_completion_timeout(struct completion *x,
+extern void __wait_for_completion(struct completion *);
+extern void __wait_for_completion_io(struct completion *);
+extern int __wait_for_completion_interruptible(struct completion *x);
+extern int __wait_for_completion_killable(struct completion *x);
+extern unsigned long __wait_for_completion_timeout(struct completion *x,
unsigned long timeout);
-extern unsigned long wait_for_completion_io_timeout(struct completion *x,
+extern unsigned long __wait_for_completion_io_timeout(struct completion *x,
unsigned long timeout);
-extern long wait_for_completion_interruptible_timeout(
+extern long __wait_for_completion_interruptible_timeout(
struct completion *x, unsigned long timeout);
-extern long wait_for_completion_killable_timeout(
+extern long __wait_for_completion_killable_timeout(
struct completion *x, unsigned long timeout);
+
+static inline void wait_for_completion(struct completion *x)
+{
+ complete_acquire(x);
+ __wait_for_completion(x);
+ complete_release(x);
+}
+
+static inline void wait_for_completion_io(struct completion *x)
+{
+ complete_acquire(x);
+ __wait_for_completion_io(x);
+ complete_release(x);
+}
+
+static inline int wait_for_completion_interruptible(struct completion *x)
+{
+ int ret;
+ complete_acquire(x);
+ ret = __wait_for_completion_interruptible(x);
+ complete_release(x);
+ return ret;
+}
+
+static inline int wait_for_completion_killable(struct completion *x)
+{
+ int ret;
+ complete_acquire(x);
+ ret = __wait_for_completion_killable(x);
+ complete_release(x);
+ return ret;
+}
+
+static inline unsigned long wait_for_completion_timeout(struct completion *x,
+ unsigned long timeout)
+{
+ return __wait_for_completion_timeout(x, timeout);
+}
+
+static inline unsigned long wait_for_completion_io_timeout(struct completion *x,
+ unsigned long timeout)
+{
+ return __wait_for_completion_io_timeout(x, timeout);
+}
+
+static inline long wait_for_completion_interruptible_timeout(
+ struct completion *x, unsigned long timeout)
+{
+ return __wait_for_completion_interruptible_timeout(x, timeout);
+}
+
+static inline long wait_for_completion_killable_timeout(
+ struct completion *x, unsigned long timeout)
+{
+ return __wait_for_completion_killable_timeout(x, timeout);
+}
+
extern bool try_wait_for_completion(struct completion *x);
extern bool completion_done(struct completion *x);

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index cb1a600..fea69ac 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4794,6 +4794,12 @@ static void add_plock(struct held_lock *hlock, unsigned int prev_gen_id,
}
}

+#ifdef CONFIG_LOCKDEP_COMPLETE
+static int xlock_might_onstack = 1;
+#else
+static int xlock_might_onstack = 0;
+#endif
+
/*
* No contention. Irq disable is only required.
*/
@@ -4839,6 +4845,14 @@ static void check_add_plock(struct held_lock *hlock)
if (!current->plocks || !depend_before(hlock))
return;

+ /*
+ * If a xlock instance is on stack, it can be overwritten randomly
+ * after escaping the stack frame, so we cannot refer to rcu list
+ * without holding lock.
+ */
+ if (xlock_might_onstack && !graph_lock())
+ return;
+
gen_id = (unsigned int)atomic_read(&cross_gen_id);
gen_id_e = gen_id_done();
start = current->held_locks;
@@ -4862,6 +4876,9 @@ static void check_add_plock(struct held_lock *hlock)
break;
}
}
+
+ if (xlock_might_onstack)
+ graph_unlock();
}

/*
diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c
index 8d0f35d..a8b2167 100644
--- a/kernel/sched/completion.c
+++ b/kernel/sched/completion.c
@@ -31,6 +31,10 @@ void complete(struct completion *x)
unsigned long flags;

spin_lock_irqsave(&x->wait.lock, flags);
+ /*
+ * Lock dependency should be built here.
+ */
+ complete_release_commit(x);
x->done++;
__wake_up_locked(&x->wait, TASK_NORMAL, 1);
spin_unlock_irqrestore(&x->wait.lock, flags);
@@ -108,7 +112,7 @@ wait_for_common_io(struct completion *x, long timeout, int state)
}

/**
- * wait_for_completion: - waits for completion of a task
+ * __wait_for_completion: - waits for completion of a task
* @x: holds the state of this particular completion
*
* This waits to be signaled for completion of a specific task. It is NOT
@@ -117,14 +121,14 @@ wait_for_common_io(struct completion *x, long timeout, int state)
* See also similar routines (i.e. wait_for_completion_timeout()) with timeout
* and interrupt capability. Also see complete().
*/
-void __sched wait_for_completion(struct completion *x)
+void __sched __wait_for_completion(struct completion *x)
{
wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
}
-EXPORT_SYMBOL(wait_for_completion);
+EXPORT_SYMBOL(__wait_for_completion);

/**
- * wait_for_completion_timeout: - waits for completion of a task (w/timeout)
+ * __wait_for_completion_timeout: - waits for completion of a task (w/timeout)
* @x: holds the state of this particular completion
* @timeout: timeout value in jiffies
*
@@ -136,28 +140,28 @@ EXPORT_SYMBOL(wait_for_completion);
* till timeout) if completed.
*/
unsigned long __sched
-wait_for_completion_timeout(struct completion *x, unsigned long timeout)
+__wait_for_completion_timeout(struct completion *x, unsigned long timeout)
{
return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE);
}
-EXPORT_SYMBOL(wait_for_completion_timeout);
+EXPORT_SYMBOL(__wait_for_completion_timeout);

/**
- * wait_for_completion_io: - waits for completion of a task
+ * __wait_for_completion_io: - waits for completion of a task
* @x: holds the state of this particular completion
*
* This waits to be signaled for completion of a specific task. It is NOT
* interruptible and there is no timeout. The caller is accounted as waiting
* for IO (which traditionally means blkio only).
*/
-void __sched wait_for_completion_io(struct completion *x)
+void __sched __wait_for_completion_io(struct completion *x)
{
wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
}
-EXPORT_SYMBOL(wait_for_completion_io);
+EXPORT_SYMBOL(__wait_for_completion_io);

/**
- * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout)
+ * __wait_for_completion_io_timeout: - waits for completion of a task (w/timeout)
* @x: holds the state of this particular completion
* @timeout: timeout value in jiffies
*
@@ -170,14 +174,14 @@ EXPORT_SYMBOL(wait_for_completion_io);
* till timeout) if completed.
*/
unsigned long __sched
-wait_for_completion_io_timeout(struct completion *x, unsigned long timeout)
+__wait_for_completion_io_timeout(struct completion *x, unsigned long timeout)
{
return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE);
}
-EXPORT_SYMBOL(wait_for_completion_io_timeout);
+EXPORT_SYMBOL(__wait_for_completion_io_timeout);

/**
- * wait_for_completion_interruptible: - waits for completion of a task (w/intr)
+ * __wait_for_completion_interruptible: - waits for completion of a task (w/intr)
* @x: holds the state of this particular completion
*
* This waits for completion of a specific task to be signaled. It is
@@ -185,17 +189,18 @@ EXPORT_SYMBOL(wait_for_completion_io_timeout);
*
* Return: -ERESTARTSYS if interrupted, 0 if completed.
*/
-int __sched wait_for_completion_interruptible(struct completion *x)
+int __sched __wait_for_completion_interruptible(struct completion *x)
{
long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE);
+
if (t == -ERESTARTSYS)
return t;
return 0;
}
-EXPORT_SYMBOL(wait_for_completion_interruptible);
+EXPORT_SYMBOL(__wait_for_completion_interruptible);

/**
- * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr))
+ * __wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr))
* @x: holds the state of this particular completion
* @timeout: timeout value in jiffies
*
@@ -206,15 +211,15 @@ EXPORT_SYMBOL(wait_for_completion_interruptible);
* or number of jiffies left till timeout) if completed.
*/
long __sched
-wait_for_completion_interruptible_timeout(struct completion *x,
+__wait_for_completion_interruptible_timeout(struct completion *x,
unsigned long timeout)
{
return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);
}
-EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
+EXPORT_SYMBOL(__wait_for_completion_interruptible_timeout);

/**
- * wait_for_completion_killable: - waits for completion of a task (killable)
+ * __wait_for_completion_killable: - waits for completion of a task (killable)
* @x: holds the state of this particular completion
*
* This waits to be signaled for completion of a specific task. It can be
@@ -222,17 +227,18 @@ EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
*
* Return: -ERESTARTSYS if interrupted, 0 if completed.
*/
-int __sched wait_for_completion_killable(struct completion *x)
+int __sched __wait_for_completion_killable(struct completion *x)
{
long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE);
+
if (t == -ERESTARTSYS)
return t;
return 0;
}
-EXPORT_SYMBOL(wait_for_completion_killable);
+EXPORT_SYMBOL(__wait_for_completion_killable);

/**
- * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable))
+ * __wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable))
* @x: holds the state of this particular completion
* @timeout: timeout value in jiffies
*
@@ -244,12 +250,12 @@ EXPORT_SYMBOL(wait_for_completion_killable);
* or number of jiffies left till timeout) if completed.
*/
long __sched
-wait_for_completion_killable_timeout(struct completion *x,
+__wait_for_completion_killable_timeout(struct completion *x,
unsigned long timeout)
{
return wait_for_common(x, timeout, TASK_KILLABLE);
}
-EXPORT_SYMBOL(wait_for_completion_killable_timeout);
+EXPORT_SYMBOL(__wait_for_completion_killable_timeout);

/**
* try_wait_for_completion - try to decrement a completion without blocking
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ef9ca8d..3466e57 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1040,6 +1040,14 @@ config LOCKDEP_CROSSRELEASE
or wait_for_complete() can use lock correctness detector using
lockdep.

+config LOCKDEP_COMPLETE
+ bool "Lock debugging: allow completions to use deadlock detector"
+ select LOCKDEP_CROSSRELEASE
+ default n
+ help
+ A deadlock caused by wait_for_completion() and complete() can be
+ detected by lockdep using crossrelease feature.
+
config PROVE_LOCKING
bool "Lock debugging: prove locking correctness"
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
--
1.9.1