Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking changes from Ingo Molnar:
 "Various updates:

   - Futex scalability improvements: remove page lock use for shared
     futex get_futex_key(), which speeds up 'perf bench futex hash'
     benchmarks by over 40% on a 60-core Westmere.  This makes anon-mem
     shared futexes perform close to private futexes.  (Mel Gorman)

   - lockdep hash collision detection and fix (Alfredo Alvarez
     Fernandez)

   - lockdep testing enhancements (Alfredo Alvarez Fernandez)

   - robustify lockdep init by using hlists (Andrew Morton, Andrey
     Ryabinin)

   - mutex and csd_lock micro-optimizations (Davidlohr Bueso)

   - small x86 barriers tweaks (Michael S Tsirkin)

   - qspinlock updates (Waiman Long)"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
  locking/csd_lock: Use smp_cond_acquire() in csd_lock_wait()
  locking/csd_lock: Explicitly inline csd_lock*() helpers
  futex: Replace barrier() in unqueue_me() with READ_ONCE()
  locking/lockdep: Detect chain_key collisions
  locking/lockdep: Prevent chain_key collisions
  tools/lib/lockdep: Fix link creation warning
  tools/lib/lockdep: Add tests for AA and ABBA locking
  tools/lib/lockdep: Add userspace version of READ_ONCE()
  tools/lib/lockdep: Fix the build on recent kernels
  locking/qspinlock: Move __ARCH_SPIN_LOCK_UNLOCKED to qspinlock_types.h
  locking/mutex: Allow next waiter lockless wakeup
  locking/pvqspinlock: Enable slowpath locking count tracking
  locking/qspinlock: Use smp_cond_acquire() in pending code
  locking/pvqspinlock: Move lock stealing count tracking code into pv_queued_spin_steal_lock()
  locking/mcs: Fix mcs_spin_lock() ordering
  futex: Remove requirement for lock_page() in get_futex_key()
  futex: Rename barrier references in ordering guarantees
  locking/atomics: Update comment about READ_ONCE() and structures
  locking/lockdep: Eliminate lockdep_init()
  locking/lockdep: Convert hash tables to hlists
  ...

kernel/futex.c

@@ -124,16 +124,16 @@
  *   futex_wait(futex, val);
  *
  *   waiters++; (a)
- *   mb(); (A) <-- paired with -.
- *                              |
- *   lock(hash_bucket(futex));  |
- *                              |
- *   uval = *futex;             |
- *                              |        *futex = newval;
- *                              |        sys_futex(WAKE, futex);
- *                              |          futex_wake(futex);
- *                              |
- *                              `------->  mb(); (B)
+ *   smp_mb(); (A) <-- paired with -.
+ *                                  |
+ *   lock(hash_bucket(futex));      |
+ *                                  |
+ *   uval = *futex;                 |
+ *                                  |        *futex = newval;
+ *                                  |        sys_futex(WAKE, futex);
+ *                                  |          futex_wake(futex);
+ *                                  |
+ *                                  `--------> smp_mb(); (B)
  *   if (uval == val)
  *     queue();
  *     unlock(hash_bucket(futex));
@@ -334,7 +334,7 @@ static inline void futex_get_mm(union futex_key *key)
 	/*
 	 * Ensure futex_get_mm() implies a full barrier such that
 	 * get_futex_key() implies a full barrier. This is relied upon
-	 * as full barrier (B), see the ordering comment above.
+	 * as smp_mb(); (B), see the ordering comment above.
 	 */
 	smp_mb__after_atomic();
 }
@@ -407,10 +407,10 @@ static void get_futex_key_refs(union futex_key *key)
 
 	switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
 	case FUT_OFF_INODE:
-		ihold(key->shared.inode); /* implies MB (B) */
+		ihold(key->shared.inode); /* implies smp_mb(); (B) */
 		break;
 	case FUT_OFF_MMSHARED:
-		futex_get_mm(key); /* implies MB (B) */
+		futex_get_mm(key); /* implies smp_mb(); (B) */
 		break;
 	default:
 		/*
@@ -418,7 +418,7 @@ static void get_futex_key_refs(union futex_key *key)
 		 * mm, therefore the only purpose of calling get_futex_key_refs
 		 * is because we need the barrier for the lockless waiter check.
 		 */
-		smp_mb(); /* explicit MB (B) */
+		smp_mb(); /* explicit smp_mb(); (B) */
 	}
 }
 
@@ -497,7 +497,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
 	if (!fshared) {
 		key->private.mm = mm;
 		key->private.address = address;
-		get_futex_key_refs(key);  /* implies MB (B) */
+		get_futex_key_refs(key);  /* implies smp_mb(); (B) */
 		return 0;
 	}
 
@@ -520,7 +520,20 @@ again:
 	else
 		err = 0;
 
-	lock_page(page);
+	/*
+	 * The treatment of mapping from this point on is critical. The page
+	 * lock protects many things but in this context the page lock
+	 * stabilizes mapping, prevents inode freeing in the shared
+	 * file-backed region case and guards against movement to swap cache.
+	 *
+	 * Strictly speaking the page lock is not needed in all cases being
+	 * considered here and page lock forces unnecessarily serialization
+	 * From this point on, mapping will be re-verified if necessary and
+	 * page lock will be acquired only if it is unavoidable
+	 */
+	page = compound_head(page);
+	mapping = READ_ONCE(page->mapping);
+
 	/*
 	 * If page->mapping is NULL, then it cannot be a PageAnon
 	 * page; but it might be the ZERO_PAGE or in the gate area or
@@ -536,19 +549,31 @@ again:
 	 * shmem_writepage move it from filecache to swapcache beneath us:
 	 * an unlikely race, but we do need to retry for page->mapping.
 	 */
-	mapping = compound_head(page)->mapping;
-	if (!mapping) {
-		int shmem_swizzled = PageSwapCache(page);
+	if (unlikely(!mapping)) {
+		int shmem_swizzled;
+
+		/*
+		 * Page lock is required to identify which special case above
+		 * applies. If this is really a shmem page then the page lock
+		 * will prevent unexpected transitions.
+		 */
+		lock_page(page);
+		shmem_swizzled = PageSwapCache(page) || page->mapping;
 		unlock_page(page);
 		put_page(page);
+
 		if (shmem_swizzled)
 			goto again;
+
 		return -EFAULT;
 	}
 
 	/*
 	 * Private mappings are handled in a simple way.
 	 *
+	 * If the futex key is stored on an anonymous page, then the associated
+	 * object is the mm which is implicitly pinned by the calling process.
+	 *
 	 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
 	 * it's a read-only handle, it's expected that futexes attach to
 	 * the object not the particular process.
@@ -566,16 +591,74 @@ again:
 		key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
 		key->private.mm = mm;
 		key->private.address = address;
+
+		get_futex_key_refs(key); /* implies smp_mb(); (B) */
+
 	} else {
+		struct inode *inode;
+
+		/*
+		 * The associated futex object in this case is the inode and
+		 * the page->mapping must be traversed. Ordinarily this should
+		 * be stabilised under page lock but it's not strictly
+		 * necessary in this case as we just want to pin the inode, not
+		 * update the radix tree or anything like that.
+		 *
+		 * The RCU read lock is taken as the inode is finally freed
+		 * under RCU. If the mapping still matches expectations then the
+		 * mapping->host can be safely accessed as being a valid inode.
+		 */
+		rcu_read_lock();
+
+		if (READ_ONCE(page->mapping) != mapping) {
+			rcu_read_unlock();
+			put_page(page);
+
+			goto again;
+		}
+
+		inode = READ_ONCE(mapping->host);
+		if (!inode) {
+			rcu_read_unlock();
+			put_page(page);
+
+			goto again;
+		}
+
+		/*
+		 * Take a reference unless it is about to be freed. Previously
+		 * this reference was taken by ihold under the page lock
+		 * pinning the inode in place so i_lock was unnecessary. The
+		 * only way for this check to fail is if the inode was
+		 * truncated in parallel so warn for now if this happens.
+		 *
+		 * We are not calling into get_futex_key_refs() in file-backed
+		 * cases, therefore a successful atomic_inc return below will
+		 * guarantee that get_futex_key() will still imply smp_mb(); (B).
+		 */
+		if (WARN_ON_ONCE(!atomic_inc_not_zero(&inode->i_count))) {
+			rcu_read_unlock();
+			put_page(page);
+
+			goto again;
+		}
+
+		/* Should be impossible but lets be paranoid for now */
+		if (WARN_ON_ONCE(inode->i_mapping != mapping)) {
+			err = -EFAULT;
+			rcu_read_unlock();
+			iput(inode);
+
+			goto out;
+		}
+
 		key->both.offset |= FUT_OFF_INODE; /* inode-based key */
-		key->shared.inode = mapping->host;
+		key->shared.inode = inode;
 		key->shared.pgoff = basepage_index(page);
+		rcu_read_unlock();
 	}
 
-	get_futex_key_refs(key); /* implies MB (B) */
-
 out:
-	unlock_page(page);
 	put_page(page);
 	return err;
 }
@@ -1864,7 +1947,7 @@ static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
 
 	q->lock_ptr = &hb->lock;
 
-	spin_lock(&hb->lock); /* implies MB (A) */
+	spin_lock(&hb->lock); /* implies smp_mb(); (A) */
 	return hb;
 }
 
@@ -1927,8 +2010,12 @@ static int unqueue_me(struct futex_q *q)
 
 	/* In the common case we don't take the spinlock, which is nice. */
 retry:
-	lock_ptr = q->lock_ptr;
-	barrier();
+	/*
+	 * q->lock_ptr can change between this read and the following spin_lock.
+	 * Use READ_ONCE to forbid the compiler from reloading q->lock_ptr and
+	 * optimizing lock_ptr out of the logic below.
+	 */
+	lock_ptr = READ_ONCE(q->lock_ptr);
 	if (lock_ptr != NULL) {
 		spin_lock(lock_ptr);
 		/*

kernel/locking/lockdep.c

@@ -123,8 +123,6 @@ static inline int debug_locks_off_graph_unlock(void)
 	return ret;
 }
 
-static int lockdep_initialized;
-
 unsigned long nr_list_entries;
 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
 
@@ -433,19 +431,6 @@ unsigned int nr_process_chains;
 unsigned int max_lockdep_depth;
 
 #ifdef CONFIG_DEBUG_LOCKDEP
-/*
- * We cannot printk in early bootup code. Not even early_printk()
- * might work. So we mark any initialization errors and printk
- * about it later on, in lockdep_info().
- */
-static int lockdep_init_error;
-static const char *lock_init_error;
-static unsigned long lockdep_init_trace_data[20];
-static struct stack_trace lockdep_init_trace = {
-	.max_entries = ARRAY_SIZE(lockdep_init_trace_data),
-	.entries = lockdep_init_trace_data,
-};
-
 /*
  * Various lockdep statistics:
  */
@@ -669,20 +654,6 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
 	struct hlist_head *hash_head;
 	struct lock_class *class;
 
-#ifdef CONFIG_DEBUG_LOCKDEP
-	/*
-	 * If the architecture calls into lockdep before initializing
-	 * the hashes then we'll warn about it later. (we cannot printk
-	 * right now)
-	 */
-	if (unlikely(!lockdep_initialized)) {
-		lockdep_init();
-		lockdep_init_error = 1;
-		lock_init_error = lock->name;
-		save_stack_trace(&lockdep_init_trace);
-	}
-#endif
-
 	if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
 		debug_locks_off();
 		printk(KERN_ERR
@@ -2010,6 +1981,53 @@ struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
 	return lock_classes + chain_hlocks[chain->base + i];
 }
 
+/*
+ * Returns the index of the first held_lock of the current chain
+ */
+static inline int get_first_held_lock(struct task_struct *curr,
+					struct held_lock *hlock)
+{
+	int i;
+	struct held_lock *hlock_curr;
+
+	for (i = curr->lockdep_depth - 1; i >= 0; i--) {
+		hlock_curr = curr->held_locks + i;
+		if (hlock_curr->irq_context != hlock->irq_context)
+			break;
+
+	}
+
+	return ++i;
+}
+
+/*
+ * Checks whether the chain and the current held locks are consistent
+ * in depth and also in content. If they are not it most likely means
+ * that there was a collision during the calculation of the chain_key.
+ * Returns: 0 not passed, 1 passed
+ */
+static int check_no_collision(struct task_struct *curr,
+			struct held_lock *hlock,
+			struct lock_chain *chain)
+{
+#ifdef CONFIG_DEBUG_LOCKDEP
+	int i, j, id;
+
+	i = get_first_held_lock(curr, hlock);
+
+	if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1)))
+		return 0;
+
+	for (j = 0; j < chain->depth - 1; j++, i++) {
+		id = curr->held_locks[i].class_idx - 1;
+
+		if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id))
+			return 0;
+	}
+#endif
+	return 1;
+}
+
 /*
  * Look up a dependency chain. If the key is not present yet then
  * add it and return 1 - in this case the new dependency chain is
@@ -2023,7 +2041,6 @@ static inline int lookup_chain_cache(struct task_struct *curr,
 	struct lock_class *class = hlock_class(hlock);
 	struct hlist_head *hash_head = chainhashentry(chain_key);
 	struct lock_chain *chain;
-	struct held_lock *hlock_curr;
 	int i, j;
 
 	/*
@@ -2041,6 +2058,9 @@ static inline int lookup_chain_cache(struct task_struct *curr,
 		if (chain->chain_key == chain_key) {
 cache_hit:
 			debug_atomic_inc(chain_lookup_hits);
+			if (!check_no_collision(curr, hlock, chain))
+				return 0;
+
 			if (very_verbose(class))
 				printk("\nhash chain already cached, key: "
 					"%016Lx tail class: [%p] %s\n",
@@ -2078,13 +2098,7 @@ cache_hit:
 	chain = lock_chains + nr_lock_chains++;
 	chain->chain_key = chain_key;
 	chain->irq_context = hlock->irq_context;
-	/* Find the first held_lock of current chain */
-	for (i = curr->lockdep_depth - 1; i >= 0; i--) {
-		hlock_curr = curr->held_locks + i;
-		if (hlock_curr->irq_context != hlock->irq_context)
-			break;
-	}
-	i++;
+	i = get_first_held_lock(curr, hlock);
 	chain->depth = curr->lockdep_depth + 1 - i;
 	if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
 		chain->base = nr_chain_hlocks;
@@ -2172,7 +2186,7 @@ static void check_chain_key(struct task_struct *curr)
 {
 #ifdef CONFIG_DEBUG_LOCKDEP
 	struct held_lock *hlock, *prev_hlock = NULL;
-	unsigned int i, id;
+	unsigned int i;
 	u64 chain_key = 0;
 
 	for (i = 0; i < curr->lockdep_depth; i++) {
@@ -2189,17 +2203,16 @@ static void check_chain_key(struct task_struct *curr)
 				(unsigned long long)hlock->prev_chain_key);
 			return;
 		}
-		id = hlock->class_idx - 1;
 		/*
 		 * Whoops ran out of static storage again?
 		 */
-		if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
+		if (DEBUG_LOCKS_WARN_ON(hlock->class_idx > MAX_LOCKDEP_KEYS))
 			return;
 
 		if (prev_hlock && (prev_hlock->irq_context !=
 							hlock->irq_context))
 			chain_key = 0;
-		chain_key = iterate_chain_key(chain_key, id);
+		chain_key = iterate_chain_key(chain_key, hlock->class_idx);
 		prev_hlock = hlock;
 	}
 	if (chain_key != curr->curr_chain_key) {
@@ -3077,7 +3090,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	struct task_struct *curr = current;
 	struct lock_class *class = NULL;
 	struct held_lock *hlock;
-	unsigned int depth, id;
+	unsigned int depth;
 	int chain_head = 0;
 	int class_idx;
 	u64 chain_key;
@@ -3180,11 +3193,10 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	 * The 'key ID' is what is the most compact key value to drive
 	 * the hash, not class->key.
 	 */
-	id = class - lock_classes;
 	/*
 	 * Whoops, we did it again.. ran straight out of our static allocation.
 	 */
-	if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
+	if (DEBUG_LOCKS_WARN_ON(class_idx > MAX_LOCKDEP_KEYS))
 		return 0;
 
 	chain_key = curr->curr_chain_key;
@@ -3202,7 +3214,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 		chain_key = 0;
 		chain_head = 1;
 	}
-	chain_key = iterate_chain_key(chain_key, id);
+	chain_key = iterate_chain_key(chain_key, class_idx);
 
 	if (nest_lock && !__lock_is_held(nest_lock))
 		return print_lock_nested_lock_not_held(curr, hlock, ip);
@@ -4013,28 +4025,6 @@ out_restore:
 	raw_local_irq_restore(flags);
 }
 
-void lockdep_init(void)
-{
-	int i;
-
-	/*
-	 * Some architectures have their own start_kernel()
-	 * code which calls lockdep_init(), while we also
-	 * call lockdep_init() from the start_kernel() itself,
-	 * and we want to initialize the hashes only once:
-	 */
-	if (lockdep_initialized)
-		return;
-
-	for (i = 0; i < CLASSHASH_SIZE; i++)
-		INIT_HLIST_HEAD(classhash_table + i);
-
-	for (i = 0; i < CHAINHASH_SIZE; i++)
-		INIT_HLIST_HEAD(chainhash_table + i);
-
-	lockdep_initialized = 1;
-}
-
 void __init lockdep_info(void)
 {
 	printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
@@ -4061,14 +4051,6 @@ void __init lockdep_info(void)
 
 	printk(" per task-struct memory footprint: %lu bytes\n",
 		sizeof(struct held_lock) * MAX_LOCK_DEPTH);
-
-#ifdef CONFIG_DEBUG_LOCKDEP
-	if (lockdep_init_error) {
-		printk("WARNING: lockdep init error: lock '%s' was acquired before lockdep_init().\n", lock_init_error);
-		printk("Call stack leading to lockdep invocation was:\n");
-		print_stack_trace(&lockdep_init_trace, 0);
-	}
-#endif
 }
 
 static void

kernel/locking/mcs_spinlock.h

@@ -67,7 +67,13 @@ void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
 	node->locked = 0;
 	node->next   = NULL;
 
-	prev = xchg_acquire(lock, node);
+	/*
+	 * We rely on the full barrier with global transitivity implied by the
+	 * below xchg() to order the initialization stores above against any
+	 * observation of @node. And to provide the ACQUIRE ordering associated
+	 * with a LOCK primitive.
+	 */
+	prev = xchg(lock, node);
 	if (likely(prev == NULL)) {
 		/*
 		 * Lock acquired, don't need to set node->locked to 1. Threads

kernel/locking/mutex.c

@@ -716,6 +716,7 @@ static inline void
 __mutex_unlock_common_slowpath(struct mutex *lock, int nested)
 {
 	unsigned long flags;
+	WAKE_Q(wake_q);
 
 	/*
 	 * As a performance measurement, release the lock before doing other
@@ -743,11 +744,11 @@ __mutex_unlock_common_slowpath(struct mutex *lock, int nested)
 					   struct mutex_waiter, list);
 
 		debug_mutex_wake_waiter(lock, waiter);
-
-		wake_up_process(waiter->task);
+		wake_q_add(&wake_q, waiter->task);
 	}
 
 	spin_unlock_mutex(&lock->wait_lock, flags);
+	wake_up_q(&wake_q);
 }
 
 /*

kernel/locking/qspinlock.c

@@ -358,8 +358,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
 	 * sequentiality; this is because not all clear_pending_set_locked()
 	 * implementations imply full barriers.
 	 */
-	while ((val = smp_load_acquire(&lock->val.counter)) & _Q_LOCKED_MASK)
-		cpu_relax();
+	smp_cond_acquire(!(atomic_read(&lock->val) & _Q_LOCKED_MASK));
 
 	/*
 	 * take ownership and clear the pending bit.
@@ -435,7 +434,7 @@ queue:
 	 *
 	 * The PV pv_wait_head_or_lock function, if active, will acquire
 	 * the lock and return a non-zero value. So we have to skip the
-	 * smp_load_acquire() call. As the next PV queue head hasn't been
+	 * smp_cond_acquire() call. As the next PV queue head hasn't been
 	 * designated yet, there is no way for the locked value to become
 	 * _Q_SLOW_VAL. So both the set_locked() and the
 	 * atomic_cmpxchg_relaxed() calls will be safe.
@@ -466,7 +465,7 @@ locked:
 			break;
 		}
 		/*
-		 * The smp_load_acquire() call above has provided the necessary
+		 * The smp_cond_acquire() call above has provided the necessary
 		 * acquire semantics required for locking. At most two
 		 * iterations of this loop may be ran.
 		 */

kernel/locking/qspinlock_paravirt.h

@@ -54,6 +54,11 @@ struct pv_node {
 	u8			state;
 };
 
+/*
+ * Include queued spinlock statistics code
+ */
+#include "qspinlock_stat.h"
+
 /*
  * By replacing the regular queued_spin_trylock() with the function below,
  * it will be called once when a lock waiter enter the PV slowpath before
@@ -65,9 +70,11 @@ struct pv_node {
 static inline bool pv_queued_spin_steal_lock(struct qspinlock *lock)
 {
 	struct __qspinlock *l = (void *)lock;
+	int ret = !(atomic_read(&lock->val) & _Q_LOCKED_PENDING_MASK) &&
+		   (cmpxchg(&l->locked, 0, _Q_LOCKED_VAL) == 0);
 
-	return !(atomic_read(&lock->val) & _Q_LOCKED_PENDING_MASK) &&
-		(cmpxchg(&l->locked, 0, _Q_LOCKED_VAL) == 0);
+	qstat_inc(qstat_pv_lock_stealing, ret);
+	return ret;
 }
 
 /*
@@ -137,11 +144,6 @@ static __always_inline int trylock_clear_pending(struct qspinlock *lock)
 }
 #endif /* _Q_PENDING_BITS == 8 */
 
-/*
- * Include queued spinlock statistics code
- */
-#include "qspinlock_stat.h"
-
 /*
  * Lock and MCS node addresses hash table for fast lookup
  *
@@ -398,6 +400,11 @@ pv_wait_head_or_lock(struct qspinlock *lock, struct mcs_spinlock *node)
 	if (READ_ONCE(pn->state) == vcpu_hashed)
 		lp = (struct qspinlock **)1;
 
+	/*
+	 * Tracking # of slowpath locking operations
+	 */
+	qstat_inc(qstat_pv_lock_slowpath, true);
+
 	for (;; waitcnt++) {
 		/*
 		 * Set correct vCPU state to be used by queue node wait-early

kernel/locking/qspinlock_stat.h

@@ -22,6 +22,7 @@
  *   pv_kick_wake	- # of vCPU kicks used for computing pv_latency_wake
  *   pv_latency_kick	- average latency (ns) of vCPU kick operation
  *   pv_latency_wake	- average latency (ns) from vCPU kick to wakeup
+ *   pv_lock_slowpath	- # of locking operations via the slowpath
  *   pv_lock_stealing	- # of lock stealing operations
  *   pv_spurious_wakeup	- # of spurious wakeups
  *   pv_wait_again	- # of vCPU wait's that happened after a vCPU kick
@@ -45,6 +46,7 @@ enum qlock_stats {
 	qstat_pv_kick_wake,
 	qstat_pv_latency_kick,
 	qstat_pv_latency_wake,
+	qstat_pv_lock_slowpath,
 	qstat_pv_lock_stealing,
 	qstat_pv_spurious_wakeup,
 	qstat_pv_wait_again,
@@ -70,6 +72,7 @@ static const char * const qstat_names[qstat_num + 1] = {
 	[qstat_pv_spurious_wakeup] = "pv_spurious_wakeup",
 	[qstat_pv_latency_kick]	   = "pv_latency_kick",
 	[qstat_pv_latency_wake]    = "pv_latency_wake",
+	[qstat_pv_lock_slowpath]   = "pv_lock_slowpath",
 	[qstat_pv_lock_stealing]   = "pv_lock_stealing",
 	[qstat_pv_wait_again]      = "pv_wait_again",
 	[qstat_pv_wait_early]      = "pv_wait_early",
@@ -279,19 +282,6 @@ static inline void __pv_wait(u8 *ptr, u8 val)
 #define pv_kick(c)	__pv_kick(c)
 #define pv_wait(p, v)	__pv_wait(p, v)
 
-/*
- * PV unfair trylock count tracking function
- */
-static inline int qstat_spin_steal_lock(struct qspinlock *lock)
-{
-	int ret = pv_queued_spin_steal_lock(lock);
-
-	qstat_inc(qstat_pv_lock_stealing, ret);
-	return ret;
-}
-#undef  queued_spin_trylock
-#define queued_spin_trylock(l)	qstat_spin_steal_lock(l)
-
 #else /* CONFIG_QUEUED_LOCK_STAT */
 
 static inline void qstat_inc(enum qlock_stats stat, bool cond)	{ }

kernel/smp.c

@@ -105,13 +105,12 @@ void __init call_function_init(void)
  * previous function call. For multi-cpu calls its even more interesting
  * as we'll have to ensure no other cpu is observing our csd.
  */
-static void csd_lock_wait(struct call_single_data *csd)
+static __always_inline void csd_lock_wait(struct call_single_data *csd)
 {
-	while (smp_load_acquire(&csd->flags) & CSD_FLAG_LOCK)
-		cpu_relax();
+	smp_cond_acquire(!(csd->flags & CSD_FLAG_LOCK));
 }
 
-static void csd_lock(struct call_single_data *csd)
+static __always_inline void csd_lock(struct call_single_data *csd)
 {
 	csd_lock_wait(csd);
 	csd->flags |= CSD_FLAG_LOCK;
@@ -124,7 +123,7 @@ static void csd_lock(struct call_single_data *csd)
 	smp_wmb();
 }
 
-static void csd_unlock(struct call_single_data *csd)
+static __always_inline void csd_unlock(struct call_single_data *csd)
 {
 	WARN_ON(!(csd->flags & CSD_FLAG_LOCK));