1 files changed, 57 insertions, 23 deletions

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index ebfc02f151e3..07fb4d717039 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -329,6 +329,32 @@ static void rt_mutex_wake_waiter(struct rt_mutex_waiter *waiter)
 }
 
 /*
+ * Deadlock detection is conditional:
+ *
+ * If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted
+ * if the detect argument is == RT_MUTEX_FULL_CHAINWALK.
+ *
+ * If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always
+ * conducted independent of the detect argument.
+ *
+ * If the waiter argument is NULL this indicates the deboost path and
+ * deadlock detection is disabled independent of the detect argument
+ * and the config settings.
+ */
+static bool rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter,
+					  enum rtmutex_chainwalk chwalk)
+{
+	/*
+	 * This is just a wrapper function for the following call,
+	 * because debug_rt_mutex_detect_deadlock() smells like a magic
+	 * debug feature and I wanted to keep the cond function in the
+	 * main source file along with the comments instead of having
+	 * two of the same in the headers.
+	 */
+	return debug_rt_mutex_detect_deadlock(waiter, chwalk);
+}
+
+/*
  * Max number of times we'll walk the boosting chain:
  */
 int max_lock_depth = 1024;
@@ -402,7 +428,7 @@ static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p)
  *	  goto again;
  */
 static int rt_mutex_adjust_prio_chain(struct task_struct *task,
-				      int deadlock_detect,
+				      enum rtmutex_chainwalk chwalk,
 				      struct rt_mutex *orig_lock,
 				      struct rt_mutex *next_lock,
 				      struct rt_mutex_waiter *orig_waiter,
@@ -410,12 +436,12 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
 {
 	struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
 	struct rt_mutex_waiter *prerequeue_top_waiter;
-	int detect_deadlock, ret = 0, depth = 0;
+	int ret = 0, depth = 0;
 	struct rt_mutex *lock;
+	bool detect_deadlock;
 	unsigned long flags;
 
-	detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter,
-							 deadlock_detect);
+	detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk);
 
 	/*
 	 * The (de)boosting is a step by step approach with a lot of
@@ -541,7 +567,7 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
 	 * walk, we detected a deadlock.
 	 */
 	if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
-		debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
+		debug_rt_mutex_deadlock(chwalk, orig_waiter, lock);
 		raw_spin_unlock(&lock->wait_lock);
 		ret = -EDEADLK;
 		goto out_unlock_pi;
@@ -835,7 +861,7 @@ try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
 static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
 				   struct rt_mutex_waiter *waiter,
 				   struct task_struct *task,
-				   int detect_deadlock)
+				   enum rtmutex_chainwalk chwalk)
 {
 	struct task_struct *owner = rt_mutex_owner(lock);
 	struct rt_mutex_waiter *top_waiter = waiter;
@@ -898,7 +924,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
 		__rt_mutex_adjust_prio(owner);
 		if (rt_mutex_real_waiter(owner->pi_blocked_on))
 			chain_walk = 1;
-	} else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) {
+	} else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) {
 		chain_walk = 1;
 	}
 
@@ -923,7 +949,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
 
 	raw_spin_unlock(&lock->wait_lock);
 
-	res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock,
+	res = rt_mutex_adjust_prio_chain(owner, chwalk, lock,
 					 next_lock, waiter, task);
 
 	raw_spin_lock(&lock->wait_lock);
@@ -1029,7 +1055,8 @@ static void remove_waiter(struct rt_mutex *lock,
 
 	raw_spin_unlock(&lock->wait_lock);
 
-	rt_mutex_adjust_prio_chain(owner, 0, lock, next_lock, NULL, current);
+	rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock,
+				   next_lock, NULL, current);
 
 	raw_spin_lock(&lock->wait_lock);
 }
@@ -1058,7 +1085,8 @@ void rt_mutex_adjust_pi(struct task_struct *task)
 	/* gets dropped in rt_mutex_adjust_prio_chain()! */
 	get_task_struct(task);
 	raw_spin_unlock_irqrestore(&task->pi_lock, flags);
-	rt_mutex_adjust_prio_chain(task, 0, NULL, next_lock, NULL, task);
+	rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL,
+				   next_lock, NULL, task);
 }
 
 #ifdef CONFIG_PREEMPT_RT_FULL
@@ -1571,7 +1599,8 @@ static void ww_mutex_account_lock(struct rt_mutex *lock,
 static int __sched
 rt_mutex_slowlock(struct rt_mutex *lock, int state,
 		  struct hrtimer_sleeper *timeout,
-		  int detect_deadlock, struct ww_acquire_ctx *ww_ctx)
+		  enum rtmutex_chainwalk chwalk,
+		  struct ww_acquire_ctx *ww_ctx)
 {
 	struct rt_mutex_waiter waiter;
 	int ret = 0;
@@ -1597,7 +1626,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
 			timeout->task = NULL;
 	}
 
-	ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock);
+	ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk);
 
 	if (likely(!ret))
 		ret = __rt_mutex_slowlock(lock, state, timeout, &waiter, ww_ctx);
@@ -1606,7 +1635,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
 
 	if (unlikely(ret)) {
 		remove_waiter(lock, &waiter);
-		rt_mutex_handle_deadlock(ret, detect_deadlock, &waiter);
+		rt_mutex_handle_deadlock(ret, chwalk, &waiter);
 	} else if (ww_ctx) {
 		ww_mutex_account_lock(lock, ww_ctx);
 	}
@@ -1737,30 +1766,32 @@ rt_mutex_fastlock(struct rt_mutex *lock, int state,
 		  struct ww_acquire_ctx *ww_ctx,
 		  int (*slowfn)(struct rt_mutex *lock, int state,
 				struct hrtimer_sleeper *timeout,
-				int detect_deadlock,
+				enum rtmutex_chainwalk chwalk,
 				struct ww_acquire_ctx *ww_ctx))
 {
 	if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
 		rt_mutex_deadlock_account_lock(lock, current);
 		return 0;
 	} else
-		return slowfn(lock, state, NULL, 0, ww_ctx);
+		return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK, ww_ctx);
 }
 
 static inline int
 rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
-			struct hrtimer_sleeper *timeout, int detect_deadlock,
+			struct hrtimer_sleeper *timeout,
+			enum rtmutex_chainwalk chwalk,
 			struct ww_acquire_ctx *ww_ctx,
 			int (*slowfn)(struct rt_mutex *lock, int state,
 				      struct hrtimer_sleeper *timeout,
-				      int detect_deadlock,
+				      enum rtmutex_chainwalk chwalk,
 				      struct ww_acquire_ctx *ww_ctx))
 {
-	if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
+	if (chwalk == RT_MUTEX_MIN_CHAINWALK &&
+	    likely(rt_mutex_cmpxchg(lock, NULL, current))) {
 		rt_mutex_deadlock_account_lock(lock, current);
 		return 0;
 	} else
-		return slowfn(lock, state, timeout, detect_deadlock, ww_ctx);
+		return slowfn(lock, state, timeout, chwalk, ww_ctx);
 }
 
 static inline int
@@ -1822,8 +1853,9 @@ int rt_mutex_timed_futex_lock(struct rt_mutex *lock,
 {
 	might_sleep();
 
-	return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, 1,
-				       NULL, rt_mutex_slowlock);
+	return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
+				       RT_MUTEX_FULL_CHAINWALK, NULL,
+				       rt_mutex_slowlock);
 }
 
 /**
@@ -1863,7 +1895,8 @@ rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout)
 {
 	might_sleep();
 
-	return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, 0,
+	return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
+				       RT_MUTEX_MIN_CHAINWALK,
 				       NULL, rt_mutex_slowlock);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
@@ -2020,7 +2053,8 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
 #endif
 
 	/* We enforce deadlock detection for futexes */
-	ret = task_blocks_on_rt_mutex(lock, waiter, task, 1);
+	ret = task_blocks_on_rt_mutex(lock, waiter, task,
+				      RT_MUTEX_FULL_CHAINWALK);
 
 	if (ret && !rt_mutex_owner(lock)) {
 		/*