x86, locking/spinlocks: Remove ticket (spin)lock implementation

We've unconditionally used the queued spinlock for many releases now.

Its time to remove the old ticket lock code.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <waiman.long@hpe.com>
Cc: Waiman.Long@hpe.com
Cc: david.vrabel@citrix.com
Cc: dhowells@redhat.com
Cc: pbonzini@redhat.com
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/20160518184302.GO3193@twins.programming.kicks-ass.netSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/Kconfig

@@ -705,7 +705,6 @@ config PARAVIRT_DEBUG
 config PARAVIRT_SPINLOCKS
 	bool "Paravirtualization layer for spinlocks"
 	depends on PARAVIRT && SMP
-	select UNINLINE_SPIN_UNLOCK if !QUEUED_SPINLOCKS
 	---help---
 	  Paravirtualized spinlocks allow a pvops backend to replace the
 	  spinlock implementation with something virtualization-friendly
@@ -718,7 +717,7 @@ config PARAVIRT_SPINLOCKS
 
 config QUEUED_LOCK_STAT
 	bool "Paravirt queued spinlock statistics"
-	depends on PARAVIRT_SPINLOCKS && DEBUG_FS && QUEUED_SPINLOCKS
+	depends on PARAVIRT_SPINLOCKS && DEBUG_FS
 	---help---
 	  Enable the collection of statistical data on the slowpath
 	  behavior of paravirtualized queued spinlocks and report

arch/x86/include/asm/paravirt.h

@@ -661,8 +661,6 @@ static inline void __set_fixmap(unsigned /* enum fixed_addresses */ idx,
 
 #if defined(CONFIG_SMP) && defined(CONFIG_PARAVIRT_SPINLOCKS)
 
-#ifdef CONFIG_QUEUED_SPINLOCKS
-
 static __always_inline void pv_queued_spin_lock_slowpath(struct qspinlock *lock,
 							u32 val)
 {
@@ -684,22 +682,6 @@ static __always_inline void pv_kick(int cpu)
 	PVOP_VCALL1(pv_lock_ops.kick, cpu);
 }
 
-#else /* !CONFIG_QUEUED_SPINLOCKS */
-
-static __always_inline void __ticket_lock_spinning(struct arch_spinlock *lock,
-							__ticket_t ticket)
-{
-	PVOP_VCALLEE2(pv_lock_ops.lock_spinning, lock, ticket);
-}
-
-static __always_inline void __ticket_unlock_kick(struct arch_spinlock *lock,
-							__ticket_t ticket)
-{
-	PVOP_VCALL2(pv_lock_ops.unlock_kick, lock, ticket);
-}
-
-#endif /* CONFIG_QUEUED_SPINLOCKS */
-
 #endif /* SMP && PARAVIRT_SPINLOCKS */
 
 #ifdef CONFIG_X86_32

arch/x86/include/asm/paravirt_types.h

@@ -301,23 +301,16 @@ struct pv_mmu_ops {
 struct arch_spinlock;
 #ifdef CONFIG_SMP
 #include <asm/spinlock_types.h>
-#else
-typedef u16 __ticket_t;
 #endif
 
 struct qspinlock;
 
 struct pv_lock_ops {
-#ifdef CONFIG_QUEUED_SPINLOCKS
 	void (*queued_spin_lock_slowpath)(struct qspinlock *lock, u32 val);
 	struct paravirt_callee_save queued_spin_unlock;
 
 	void (*wait)(u8 *ptr, u8 val);
 	void (*kick)(int cpu);
-#else /* !CONFIG_QUEUED_SPINLOCKS */
-	struct paravirt_callee_save lock_spinning;
-	void (*unlock_kick)(struct arch_spinlock *lock, __ticket_t ticket);
-#endif /* !CONFIG_QUEUED_SPINLOCKS */
 };
 
 /* This contains all the paravirt structures: we get a convenient

arch/x86/include/asm/spinlock.h

@@ -20,187 +20,13 @@
  * (the type definitions are in asm/spinlock_types.h)
  */
 
-#ifdef CONFIG_X86_32
-# define LOCK_PTR_REG "a"
-#else
-# define LOCK_PTR_REG "D"
-#endif
-
-#if defined(CONFIG_X86_32) && (defined(CONFIG_X86_PPRO_FENCE))
-/*
- * On PPro SMP, we use a locked operation to unlock
- * (PPro errata 66, 92)
- */
-# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
-#else
-# define UNLOCK_LOCK_PREFIX
-#endif
-
 /* How long a lock should spin before we consider blocking */
 #define SPIN_THRESHOLD	(1 << 15)
 
 extern struct static_key paravirt_ticketlocks_enabled;
 static __always_inline bool static_key_false(struct static_key *key);
 
-#ifdef CONFIG_QUEUED_SPINLOCKS
 #include <asm/qspinlock.h>
-#else
-
-#ifdef CONFIG_PARAVIRT_SPINLOCKS
-
-static inline void __ticket_enter_slowpath(arch_spinlock_t *lock)
-{
-	set_bit(0, (volatile unsigned long *)&lock->tickets.head);
-}
-
-#else  /* !CONFIG_PARAVIRT_SPINLOCKS */
-static __always_inline void __ticket_lock_spinning(arch_spinlock_t *lock,
-							__ticket_t ticket)
-{
-}
-static inline void __ticket_unlock_kick(arch_spinlock_t *lock,
-							__ticket_t ticket)
-{
-}
-
-#endif /* CONFIG_PARAVIRT_SPINLOCKS */
-static inline int  __tickets_equal(__ticket_t one, __ticket_t two)
-{
-	return !((one ^ two) & ~TICKET_SLOWPATH_FLAG);
-}
-
-static inline void __ticket_check_and_clear_slowpath(arch_spinlock_t *lock,
-							__ticket_t head)
-{
-	if (head & TICKET_SLOWPATH_FLAG) {
-		arch_spinlock_t old, new;
-
-		old.tickets.head = head;
-		new.tickets.head = head & ~TICKET_SLOWPATH_FLAG;
-		old.tickets.tail = new.tickets.head + TICKET_LOCK_INC;
-		new.tickets.tail = old.tickets.tail;
-
-		/* try to clear slowpath flag when there are no contenders */
-		cmpxchg(&lock->head_tail, old.head_tail, new.head_tail);
-	}
-}
-
-static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
-{
-	return __tickets_equal(lock.tickets.head, lock.tickets.tail);
-}
-
-/*
- * Ticket locks are conceptually two parts, one indicating the current head of
- * the queue, and the other indicating the current tail. The lock is acquired
- * by atomically noting the tail and incrementing it by one (thus adding
- * ourself to the queue and noting our position), then waiting until the head
- * becomes equal to the the initial value of the tail.
- *
- * We use an xadd covering *both* parts of the lock, to increment the tail and
- * also load the position of the head, which takes care of memory ordering
- * issues and should be optimal for the uncontended case. Note the tail must be
- * in the high part, because a wide xadd increment of the low part would carry
- * up and contaminate the high part.
- */
-static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
-{
-	register struct __raw_tickets inc = { .tail = TICKET_LOCK_INC };
-
-	inc = xadd(&lock->tickets, inc);
-	if (likely(inc.head == inc.tail))
-		goto out;
-
-	for (;;) {
-		unsigned count = SPIN_THRESHOLD;
-
-		do {
-			inc.head = READ_ONCE(lock->tickets.head);
-			if (__tickets_equal(inc.head, inc.tail))
-				goto clear_slowpath;
-			cpu_relax();
-		} while (--count);
-		__ticket_lock_spinning(lock, inc.tail);
-	}
-clear_slowpath:
-	__ticket_check_and_clear_slowpath(lock, inc.head);
-out:
-	barrier();	/* make sure nothing creeps before the lock is taken */
-}
-
-static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
-{
-	arch_spinlock_t old, new;
-
-	old.tickets = READ_ONCE(lock->tickets);
-	if (!__tickets_equal(old.tickets.head, old.tickets.tail))
-		return 0;
-
-	new.head_tail = old.head_tail + (TICKET_LOCK_INC << TICKET_SHIFT);
-	new.head_tail &= ~TICKET_SLOWPATH_FLAG;
-
-	/* cmpxchg is a full barrier, so nothing can move before it */
-	return cmpxchg(&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail;
-}
-
-static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
-{
-	if (TICKET_SLOWPATH_FLAG &&
-		static_key_false(&paravirt_ticketlocks_enabled)) {
-		__ticket_t head;
-
-		BUILD_BUG_ON(((__ticket_t)NR_CPUS) != NR_CPUS);
-
-		head = xadd(&lock->tickets.head, TICKET_LOCK_INC);
-
-		if (unlikely(head & TICKET_SLOWPATH_FLAG)) {
-			head &= ~TICKET_SLOWPATH_FLAG;
-			__ticket_unlock_kick(lock, (head + TICKET_LOCK_INC));
-		}
-	} else
-		__add(&lock->tickets.head, TICKET_LOCK_INC, UNLOCK_LOCK_PREFIX);
-}
-
-static inline int arch_spin_is_locked(arch_spinlock_t *lock)
-{
-	struct __raw_tickets tmp = READ_ONCE(lock->tickets);
-
-	return !__tickets_equal(tmp.tail, tmp.head);
-}
-
-static inline int arch_spin_is_contended(arch_spinlock_t *lock)
-{
-	struct __raw_tickets tmp = READ_ONCE(lock->tickets);
-
-	tmp.head &= ~TICKET_SLOWPATH_FLAG;
-	return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC;
-}
-#define arch_spin_is_contended	arch_spin_is_contended
-
-static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock,
-						  unsigned long flags)
-{
-	arch_spin_lock(lock);
-}
-
-static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
-{
-	__ticket_t head = READ_ONCE(lock->tickets.head);
-
-	for (;;) {
-		struct __raw_tickets tmp = READ_ONCE(lock->tickets);
-		/*
-		 * We need to check "unlocked" in a loop, tmp.head == head
-		 * can be false positive because of overflow.
-		 */
-		if (__tickets_equal(tmp.head, tmp.tail) ||
-				!__tickets_equal(tmp.head, head))
-			break;
-
-		cpu_relax();
-	}
-}
-#endif /* CONFIG_QUEUED_SPINLOCKS */
 
 /*
  * Read-write spinlocks, allowing multiple readers

arch/x86/include/asm/spinlock_types.h

@@ -23,20 +23,7 @@ typedef u32 __ticketpair_t;
 
 #define TICKET_SHIFT	(sizeof(__ticket_t) * 8)
 
-#ifdef CONFIG_QUEUED_SPINLOCKS
 #include <asm-generic/qspinlock_types.h>
-#else
-typedef struct arch_spinlock {
-	union {
-		__ticketpair_t head_tail;
-		struct __raw_tickets {
-			__ticket_t head, tail;
-		} tickets;
-	};
-} arch_spinlock_t;
-
-#define __ARCH_SPIN_LOCK_UNLOCKED	{ { 0 } }
-#endif /* CONFIG_QUEUED_SPINLOCKS */
 
 #include <asm-generic/qrwlock_types.h>
 

arch/x86/kernel/kvm.c

@@ -575,9 +575,6 @@ static void kvm_kick_cpu(int cpu)
 	kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
 }
 
-
-#ifdef CONFIG_QUEUED_SPINLOCKS
-
 #include <asm/qspinlock.h>
 
 static void kvm_wait(u8 *ptr, u8 val)
@@ -606,243 +603,6 @@ static void kvm_wait(u8 *ptr, u8 val)
 	local_irq_restore(flags);
 }
 
-#else /* !CONFIG_QUEUED_SPINLOCKS */
-
-enum kvm_contention_stat {
-	TAKEN_SLOW,
-	TAKEN_SLOW_PICKUP,
-	RELEASED_SLOW,
-	RELEASED_SLOW_KICKED,
-	NR_CONTENTION_STATS
-};
-
-#ifdef CONFIG_KVM_DEBUG_FS
-#define HISTO_BUCKETS	30
-
-static struct kvm_spinlock_stats
-{
-	u32 contention_stats[NR_CONTENTION_STATS];
-	u32 histo_spin_blocked[HISTO_BUCKETS+1];
-	u64 time_blocked;
-} spinlock_stats;
-
-static u8 zero_stats;
-
-static inline void check_zero(void)
-{
-	u8 ret;
-	u8 old;
-
-	old = READ_ONCE(zero_stats);
-	if (unlikely(old)) {
-		ret = cmpxchg(&zero_stats, old, 0);
-		/* This ensures only one fellow resets the stat */
-		if (ret == old)
-			memset(&spinlock_stats, 0, sizeof(spinlock_stats));
-	}
-}
-
-static inline void add_stats(enum kvm_contention_stat var, u32 val)
-{
-	check_zero();
-	spinlock_stats.contention_stats[var] += val;
-}
-
-
-static inline u64 spin_time_start(void)
-{
-	return sched_clock();
-}
-
-static void __spin_time_accum(u64 delta, u32 *array)
-{
-	unsigned index;
-
-	index = ilog2(delta);
-	check_zero();
-
-	if (index < HISTO_BUCKETS)
-		array[index]++;
-	else
-		array[HISTO_BUCKETS]++;
-}
-
-static inline void spin_time_accum_blocked(u64 start)
-{
-	u32 delta;
-
-	delta = sched_clock() - start;
-	__spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
-	spinlock_stats.time_blocked += delta;
-}
-
-static struct dentry *d_spin_debug;
-static struct dentry *d_kvm_debug;
-
-static struct dentry *kvm_init_debugfs(void)
-{
-	d_kvm_debug = debugfs_create_dir("kvm-guest", NULL);
-	if (!d_kvm_debug)
-		printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n");
-
-	return d_kvm_debug;
-}
-
-static int __init kvm_spinlock_debugfs(void)
-{
-	struct dentry *d_kvm;
-
-	d_kvm = kvm_init_debugfs();
-	if (d_kvm == NULL)
-		return -ENOMEM;
-
-	d_spin_debug = debugfs_create_dir("spinlocks", d_kvm);
-
-	debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
-
-	debugfs_create_u32("taken_slow", 0444, d_spin_debug,
-		   &spinlock_stats.contention_stats[TAKEN_SLOW]);
-	debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
-		   &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]);
-
-	debugfs_create_u32("released_slow", 0444, d_spin_debug,
-		   &spinlock_stats.contention_stats[RELEASED_SLOW]);
-	debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
-		   &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]);
-
-	debugfs_create_u64("time_blocked", 0444, d_spin_debug,
-			   &spinlock_stats.time_blocked);
-
-	debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
-		     spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
-
-	return 0;
-}
-fs_initcall(kvm_spinlock_debugfs);
-#else  /* !CONFIG_KVM_DEBUG_FS */
-static inline void add_stats(enum kvm_contention_stat var, u32 val)
-{
-}
-
-static inline u64 spin_time_start(void)
-{
-	return 0;
-}
-
-static inline void spin_time_accum_blocked(u64 start)
-{
-}
-#endif  /* CONFIG_KVM_DEBUG_FS */
-
-struct kvm_lock_waiting {
-	struct arch_spinlock *lock;
-	__ticket_t want;
-};
-
-/* cpus 'waiting' on a spinlock to become available */
-static cpumask_t waiting_cpus;
-
-/* Track spinlock on which a cpu is waiting */
-static DEFINE_PER_CPU(struct kvm_lock_waiting, klock_waiting);
-
-__visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
-{
-	struct kvm_lock_waiting *w;
-	int cpu;
-	u64 start;
-	unsigned long flags;
-	__ticket_t head;
-
-	if (in_nmi())
-		return;
-
-	w = this_cpu_ptr(&klock_waiting);
-	cpu = smp_processor_id();
-	start = spin_time_start();
-
-	/*
-	 * Make sure an interrupt handler can't upset things in a
-	 * partially setup state.
-	 */
-	local_irq_save(flags);
-
-	/*
-	 * The ordering protocol on this is that the "lock" pointer
-	 * may only be set non-NULL if the "want" ticket is correct.
-	 * If we're updating "want", we must first clear "lock".
-	 */
-	w->lock = NULL;
-	smp_wmb();
-	w->want = want;
-	smp_wmb();
-	w->lock = lock;
-
-	add_stats(TAKEN_SLOW, 1);
-
-	/*
-	 * This uses set_bit, which is atomic but we should not rely on its
-	 * reordering gurantees. So barrier is needed after this call.
-	 */
-	cpumask_set_cpu(cpu, &waiting_cpus);
-
-	barrier();
-
-	/*
-	 * Mark entry to slowpath before doing the pickup test to make
-	 * sure we don't deadlock with an unlocker.
-	 */
-	__ticket_enter_slowpath(lock);
-
-	/* make sure enter_slowpath, which is atomic does not cross the read */
-	smp_mb__after_atomic();
-
-	/*
-	 * check again make sure it didn't become free while
-	 * we weren't looking.
-	 */
-	head = READ_ONCE(lock->tickets.head);
-	if (__tickets_equal(head, want)) {
-		add_stats(TAKEN_SLOW_PICKUP, 1);
-		goto out;
-	}
-
-	/*
-	 * halt until it's our turn and kicked. Note that we do safe halt
-	 * for irq enabled case to avoid hang when lock info is overwritten
-	 * in irq spinlock slowpath and no spurious interrupt occur to save us.
-	 */
-	if (arch_irqs_disabled_flags(flags))
-		halt();
-	else
-		safe_halt();
-
-out:
-	cpumask_clear_cpu(cpu, &waiting_cpus);
-	w->lock = NULL;
-	local_irq_restore(flags);
-	spin_time_accum_blocked(start);
-}
-PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning);
-
-/* Kick vcpu waiting on @lock->head to reach value @ticket */
-static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
-{
-	int cpu;
-
-	add_stats(RELEASED_SLOW, 1);
-	for_each_cpu(cpu, &waiting_cpus) {
-		const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu);
-		if (READ_ONCE(w->lock) == lock &&
-		    READ_ONCE(w->want) == ticket) {
-			add_stats(RELEASED_SLOW_KICKED, 1);
-			kvm_kick_cpu(cpu);
-			break;
-		}
-	}
-}
-
-#endif /* !CONFIG_QUEUED_SPINLOCKS */
-
 /*
  * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
  */
@@ -854,16 +614,11 @@ void __init kvm_spinlock_init(void)
 	if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
 		return;
 
-#ifdef CONFIG_QUEUED_SPINLOCKS
 	__pv_init_lock_hash();
 	pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
 	pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
 	pv_lock_ops.wait = kvm_wait;
 	pv_lock_ops.kick = kvm_kick_cpu;
-#else /* !CONFIG_QUEUED_SPINLOCKS */
-	pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
-	pv_lock_ops.unlock_kick = kvm_unlock_kick;
-#endif
 }
 
 static __init int kvm_spinlock_init_jump(void)

arch/x86/kernel/paravirt-spinlocks.c

@@ -8,7 +8,6 @@
 
 #include <asm/paravirt.h>
 
-#ifdef CONFIG_QUEUED_SPINLOCKS
 __visible void __native_queued_spin_unlock(struct qspinlock *lock)
 {
 	native_queued_spin_unlock(lock);
@@ -21,19 +20,13 @@ bool pv_is_native_spin_unlock(void)
 	return pv_lock_ops.queued_spin_unlock.func ==
 		__raw_callee_save___native_queued_spin_unlock;
 }
-#endif
 
 struct pv_lock_ops pv_lock_ops = {
 #ifdef CONFIG_SMP
-#ifdef CONFIG_QUEUED_SPINLOCKS
 	.queued_spin_lock_slowpath = native_queued_spin_lock_slowpath,
 	.queued_spin_unlock = PV_CALLEE_SAVE(__native_queued_spin_unlock),
 	.wait = paravirt_nop,
 	.kick = paravirt_nop,
-#else /* !CONFIG_QUEUED_SPINLOCKS */
-	.lock_spinning = __PV_IS_CALLEE_SAVE(paravirt_nop),
-	.unlock_kick = paravirt_nop,
-#endif /* !CONFIG_QUEUED_SPINLOCKS */
 #endif /* SMP */
 };
 EXPORT_SYMBOL(pv_lock_ops);

arch/x86/kernel/paravirt_patch_32.c

@@ -10,7 +10,7 @@ DEF_NATIVE(pv_mmu_ops, write_cr3, "mov %eax, %cr3");
 DEF_NATIVE(pv_mmu_ops, read_cr3, "mov %cr3, %eax");
 DEF_NATIVE(pv_cpu_ops, clts, "clts");
 
-#if defined(CONFIG_PARAVIRT_SPINLOCKS) && defined(CONFIG_QUEUED_SPINLOCKS)
+#if defined(CONFIG_PARAVIRT_SPINLOCKS)
 DEF_NATIVE(pv_lock_ops, queued_spin_unlock, "movb $0, (%eax)");
 #endif
 
@@ -49,7 +49,7 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
 		PATCH_SITE(pv_mmu_ops, read_cr3);
 		PATCH_SITE(pv_mmu_ops, write_cr3);
 		PATCH_SITE(pv_cpu_ops, clts);
-#if defined(CONFIG_PARAVIRT_SPINLOCKS) && defined(CONFIG_QUEUED_SPINLOCKS)
+#if defined(CONFIG_PARAVIRT_SPINLOCKS)
 		case PARAVIRT_PATCH(pv_lock_ops.queued_spin_unlock):
 			if (pv_is_native_spin_unlock()) {
 				start = start_pv_lock_ops_queued_spin_unlock;

arch/x86/kernel/paravirt_patch_64.c

@@ -19,7 +19,7 @@ DEF_NATIVE(pv_cpu_ops, swapgs, "swapgs");
 DEF_NATIVE(, mov32, "mov %edi, %eax");
 DEF_NATIVE(, mov64, "mov %rdi, %rax");
 
-#if defined(CONFIG_PARAVIRT_SPINLOCKS) && defined(CONFIG_QUEUED_SPINLOCKS)
+#if defined(CONFIG_PARAVIRT_SPINLOCKS)
 DEF_NATIVE(pv_lock_ops, queued_spin_unlock, "movb $0, (%rdi)");
 #endif
 
@@ -61,7 +61,7 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
 		PATCH_SITE(pv_cpu_ops, clts);
 		PATCH_SITE(pv_mmu_ops, flush_tlb_single);
 		PATCH_SITE(pv_cpu_ops, wbinvd);
-#if defined(CONFIG_PARAVIRT_SPINLOCKS) && defined(CONFIG_QUEUED_SPINLOCKS)
+#if defined(CONFIG_PARAVIRT_SPINLOCKS)
 		case PARAVIRT_PATCH(pv_lock_ops.queued_spin_unlock):
 			if (pv_is_native_spin_unlock()) {
 				start = start_pv_lock_ops_queued_spin_unlock;

arch/x86/xen/spinlock.c

@@ -21,8 +21,6 @@ static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
 static DEFINE_PER_CPU(char *, irq_name);
 static bool xen_pvspin = true;
 
-#ifdef CONFIG_QUEUED_SPINLOCKS
-
 #include <asm/qspinlock.h>
 
 static void xen_qlock_kick(int cpu)
@@ -71,207 +69,6 @@ static void xen_qlock_wait(u8 *byte, u8 val)
 	xen_poll_irq(irq);
 }
 
-#else /* CONFIG_QUEUED_SPINLOCKS */
-
-enum xen_contention_stat {
-	TAKEN_SLOW,
-	TAKEN_SLOW_PICKUP,
-	TAKEN_SLOW_SPURIOUS,
-	RELEASED_SLOW,
-	RELEASED_SLOW_KICKED,
-	NR_CONTENTION_STATS
-};
-
-
-#ifdef CONFIG_XEN_DEBUG_FS
-#define HISTO_BUCKETS	30
-static struct xen_spinlock_stats
-{
-	u32 contention_stats[NR_CONTENTION_STATS];
-	u32 histo_spin_blocked[HISTO_BUCKETS+1];
-	u64 time_blocked;
-} spinlock_stats;
-
-static u8 zero_stats;
-
-static inline void check_zero(void)
-{
-	u8 ret;
-	u8 old = READ_ONCE(zero_stats);
-	if (unlikely(old)) {
-		ret = cmpxchg(&zero_stats, old, 0);
-		/* This ensures only one fellow resets the stat */
-		if (ret == old)
-			memset(&spinlock_stats, 0, sizeof(spinlock_stats));
-	}
-}
-
-static inline void add_stats(enum xen_contention_stat var, u32 val)
-{
-	check_zero();
-	spinlock_stats.contention_stats[var] += val;
-}
-
-static inline u64 spin_time_start(void)
-{
-	return xen_clocksource_read();
-}
-
-static void __spin_time_accum(u64 delta, u32 *array)
-{
-	unsigned index = ilog2(delta);
-
-	check_zero();
-
-	if (index < HISTO_BUCKETS)
-		array[index]++;
-	else
-		array[HISTO_BUCKETS]++;
-}
-
-static inline void spin_time_accum_blocked(u64 start)
-{
-	u32 delta = xen_clocksource_read() - start;
-
-	__spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
-	spinlock_stats.time_blocked += delta;
-}
-#else  /* !CONFIG_XEN_DEBUG_FS */
-static inline void add_stats(enum xen_contention_stat var, u32 val)
-{
-}
-
-static inline u64 spin_time_start(void)
-{
-	return 0;
-}
-
-static inline void spin_time_accum_blocked(u64 start)
-{
-}
-#endif  /* CONFIG_XEN_DEBUG_FS */
-
-struct xen_lock_waiting {
-	struct arch_spinlock *lock;
-	__ticket_t want;
-};
-
-static DEFINE_PER_CPU(struct xen_lock_waiting, lock_waiting);
-static cpumask_t waiting_cpus;
-
-__visible void xen_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
-{
-	int irq = __this_cpu_read(lock_kicker_irq);
-	struct xen_lock_waiting *w = this_cpu_ptr(&lock_waiting);
-	int cpu = smp_processor_id();
-	u64 start;
-	__ticket_t head;
-	unsigned long flags;
-
-	/* If kicker interrupts not initialized yet, just spin */
-	if (irq == -1)
-		return;
-
-	start = spin_time_start();
-
-	/*
-	 * Make sure an interrupt handler can't upset things in a
-	 * partially setup state.
-	 */
-	local_irq_save(flags);
-	/*
-	 * We don't really care if we're overwriting some other
-	 * (lock,want) pair, as that would mean that we're currently
-	 * in an interrupt context, and the outer context had
-	 * interrupts enabled.  That has already kicked the VCPU out
-	 * of xen_poll_irq(), so it will just return spuriously and
-	 * retry with newly setup (lock,want).
-	 *
-	 * The ordering protocol on this is that the "lock" pointer
-	 * may only be set non-NULL if the "want" ticket is correct.
-	 * If we're updating "want", we must first clear "lock".
-	 */
-	w->lock = NULL;
-	smp_wmb();
-	w->want = want;
-	smp_wmb();
-	w->lock = lock;
-
-	/* This uses set_bit, which atomic and therefore a barrier */
-	cpumask_set_cpu(cpu, &waiting_cpus);
-	add_stats(TAKEN_SLOW, 1);
-
-	/* clear pending */
-	xen_clear_irq_pending(irq);
-
-	/* Only check lock once pending cleared */
-	barrier();
-
-	/*
-	 * Mark entry to slowpath before doing the pickup test to make
-	 * sure we don't deadlock with an unlocker.
-	 */
-	__ticket_enter_slowpath(lock);
-
-	/* make sure enter_slowpath, which is atomic does not cross the read */
-	smp_mb__after_atomic();
-
-	/*
-	 * check again make sure it didn't become free while
-	 * we weren't looking
-	 */
-	head = READ_ONCE(lock->tickets.head);
-	if (__tickets_equal(head, want)) {
-		add_stats(TAKEN_SLOW_PICKUP, 1);
-		goto out;
-	}
-
-	/* Allow interrupts while blocked */
-	local_irq_restore(flags);
-
-	/*
-	 * If an interrupt happens here, it will leave the wakeup irq
-	 * pending, which will cause xen_poll_irq() to return
-	 * immediately.
-	 */
-
-	/* Block until irq becomes pending (or perhaps a spurious wakeup) */
-	xen_poll_irq(irq);
-	add_stats(TAKEN_SLOW_SPURIOUS, !xen_test_irq_pending(irq));
-
-	local_irq_save(flags);
-
-	kstat_incr_irq_this_cpu(irq);
-out:
-	cpumask_clear_cpu(cpu, &waiting_cpus);
-	w->lock = NULL;
-
-	local_irq_restore(flags);
-
-	spin_time_accum_blocked(start);
-}
-PV_CALLEE_SAVE_REGS_THUNK(xen_lock_spinning);
-
-static void xen_unlock_kick(struct arch_spinlock *lock, __ticket_t next)
-{
-	int cpu;
-
-	add_stats(RELEASED_SLOW, 1);
-
-	for_each_cpu(cpu, &waiting_cpus) {
-		const struct xen_lock_waiting *w = &per_cpu(lock_waiting, cpu);
-
-		/* Make sure we read lock before want */
-		if (READ_ONCE(w->lock) == lock &&
-		    READ_ONCE(w->want) == next) {
-			add_stats(RELEASED_SLOW_KICKED, 1);
-			xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
-			break;
-		}
-	}
-}
-#endif /* CONFIG_QUEUED_SPINLOCKS */
-
 static irqreturn_t dummy_handler(int irq, void *dev_id)
 {
 	BUG();
@@ -334,16 +131,12 @@ void __init xen_init_spinlocks(void)
 		return;
 	}
 	printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
-#ifdef CONFIG_QUEUED_SPINLOCKS
+
 	__pv_init_lock_hash();
 	pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
 	pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
 	pv_lock_ops.wait = xen_qlock_wait;
 	pv_lock_ops.kick = xen_qlock_kick;
-#else
-	pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(xen_lock_spinning);
-	pv_lock_ops.unlock_kick = xen_unlock_kick;
-#endif
 }
 
 /*
@@ -372,44 +165,3 @@ static __init int xen_parse_nopvspin(char *arg)
 }
 early_param("xen_nopvspin", xen_parse_nopvspin);
 
-#if defined(CONFIG_XEN_DEBUG_FS) && !defined(CONFIG_QUEUED_SPINLOCKS)
-
-static struct dentry *d_spin_debug;
-
-static int __init xen_spinlock_debugfs(void)
-{
-	struct dentry *d_xen = xen_init_debugfs();
-
-	if (d_xen == NULL)
-		return -ENOMEM;
-
-	if (!xen_pvspin)
-		return 0;
-
-	d_spin_debug = debugfs_create_dir("spinlocks", d_xen);
-
-	debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
-
-	debugfs_create_u32("taken_slow", 0444, d_spin_debug,
-			   &spinlock_stats.contention_stats[TAKEN_SLOW]);
-	debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
-			   &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]);
-	debugfs_create_u32("taken_slow_spurious", 0444, d_spin_debug,
-			   &spinlock_stats.contention_stats[TAKEN_SLOW_SPURIOUS]);
-
-	debugfs_create_u32("released_slow", 0444, d_spin_debug,
-			   &spinlock_stats.contention_stats[RELEASED_SLOW]);
-	debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
-			   &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]);
-
-	debugfs_create_u64("time_blocked", 0444, d_spin_debug,
-			   &spinlock_stats.time_blocked);
-
-	debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
-				spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
-
-	return 0;
-}
-fs_initcall(xen_spinlock_debugfs);
-
-#endif	/* CONFIG_XEN_DEBUG_FS */