1 files changed, 164 insertions, 30 deletions

diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index ee73bcca7e6f..6747134227cd 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -8,8 +8,10 @@
 #include <linux/types.h>
 #include <linux/export.h>
 #include <linux/spinlock.h>
+#include <linux/jiffies.h>
 #include <linux/init.h>
 #include <linux/smp.h>
+#include <linux/percpu.h>
 #include <asm/io.h>
 
 int spin_retry = -1;
@@ -32,6 +34,40 @@ static int __init spin_retry_setup(char *str)
 }
 __setup("spin_retry=", spin_retry_setup);
 
+struct spin_wait {
+	struct spin_wait *next, *prev;
+	int node_id;
+} __aligned(32);
+
+static DEFINE_PER_CPU_ALIGNED(struct spin_wait, spin_wait[4]);
+
+#define _Q_LOCK_CPU_OFFSET	0
+#define _Q_LOCK_STEAL_OFFSET	16
+#define _Q_TAIL_IDX_OFFSET	18
+#define _Q_TAIL_CPU_OFFSET	20
+
+#define _Q_LOCK_CPU_MASK	0x0000ffff
+#define _Q_LOCK_STEAL_ADD	0x00010000
+#define _Q_LOCK_STEAL_MASK	0x00030000
+#define _Q_TAIL_IDX_MASK	0x000c0000
+#define _Q_TAIL_CPU_MASK	0xfff00000
+
+#define _Q_LOCK_MASK		(_Q_LOCK_CPU_MASK | _Q_LOCK_STEAL_MASK)
+#define _Q_TAIL_MASK		(_Q_TAIL_IDX_MASK | _Q_TAIL_CPU_MASK)
+
+void arch_spin_lock_setup(int cpu)
+{
+	struct spin_wait *node;
+	int ix;
+
+	node = per_cpu_ptr(&spin_wait[0], cpu);
+	for (ix = 0; ix < 4; ix++, node++) {
+		memset(node, 0, sizeof(*node));
+		node->node_id = ((cpu + 1) << _Q_TAIL_CPU_OFFSET) +
+			(ix << _Q_TAIL_IDX_OFFSET);
+	}
+}
+
 static inline int arch_load_niai4(int *lock)
 {
 	int owner;
@@ -60,75 +96,160 @@ static inline int arch_cmpxchg_niai8(int *lock, int old, int new)
 	return expected == old;
 }
 
-void arch_spin_lock_wait(arch_spinlock_t *lp)
+static inline struct spin_wait *arch_spin_decode_tail(int lock)
 {
-	int cpu = SPINLOCK_LOCKVAL;
-	int owner, count;
+	int ix, cpu;
+
+	ix = (lock & _Q_TAIL_IDX_MASK) >> _Q_TAIL_IDX_OFFSET;
+	cpu = (lock & _Q_TAIL_CPU_MASK) >> _Q_TAIL_CPU_OFFSET;
+	return per_cpu_ptr(&spin_wait[ix], cpu - 1);
+}
+
+static inline int arch_spin_yield_target(int lock, struct spin_wait *node)
+{
+	if (lock & _Q_LOCK_CPU_MASK)
+		return lock & _Q_LOCK_CPU_MASK;
+	if (node == NULL || node->prev == NULL)
+		return 0;	/* 0 -> no target cpu */
+	while (node->prev)
+		node = node->prev;
+	return node->node_id >> _Q_TAIL_CPU_OFFSET;
+}
+
+static inline void arch_spin_lock_queued(arch_spinlock_t *lp)
+{
+	struct spin_wait *node, *next;
+	int lockval, ix, node_id, tail_id, old, new, owner, count;
+
+	ix = S390_lowcore.spinlock_index++;
+	barrier();
+	lockval = SPINLOCK_LOCKVAL;	/* cpu + 1 */
+	node = this_cpu_ptr(&spin_wait[ix]);
+	node->prev = node->next = NULL;
+	node_id = node->node_id;
+
+	/* Enqueue the node for this CPU in the spinlock wait queue */
+	while (1) {
+		old = READ_ONCE(lp->lock);
+		if ((old & _Q_LOCK_CPU_MASK) == 0 &&
+		    (old & _Q_LOCK_STEAL_MASK) != _Q_LOCK_STEAL_MASK) {
+			/*
+			 * The lock is free but there may be waiters.
+			 * With no waiters simply take the lock, if there
+			 * are waiters try to steal the lock. The lock may
+			 * be stolen three times before the next queued
+			 * waiter will get the lock.
+			 */
+			new = (old ? (old + _Q_LOCK_STEAL_ADD) : 0) | lockval;
+			if (__atomic_cmpxchg_bool(&lp->lock, old, new))
+				/* Got the lock */
+				goto out;
+			/* lock passing in progress */
+			continue;
+		}
+		/* Make the node of this CPU the new tail. */
+		new = node_id | (old & _Q_LOCK_MASK);
+		if (__atomic_cmpxchg_bool(&lp->lock, old, new))
+			break;
+	}
+	/* Set the 'next' pointer of the tail node in the queue */
+	tail_id = old & _Q_TAIL_MASK;
+	if (tail_id != 0) {
+		node->prev = arch_spin_decode_tail(tail_id);
+		WRITE_ONCE(node->prev->next, node);
+	}
 
 	/* Pass the virtual CPU to the lock holder if it is not running */
-	owner = arch_load_niai4(&lp->lock);
+	owner = arch_spin_yield_target(old, node);
 	if (owner && arch_vcpu_is_preempted(owner - 1))
 		smp_yield_cpu(owner - 1);
 
+	/* Spin on the CPU local node->prev pointer */
+	if (tail_id != 0) {
+		count = spin_retry;
+		while (READ_ONCE(node->prev) != NULL) {
+			if (count-- >= 0)
+				continue;
+			count = spin_retry;
+			/* Query running state of lock holder again. */
+			owner = arch_spin_yield_target(old, node);
+			if (owner && arch_vcpu_is_preempted(owner - 1))
+				smp_yield_cpu(owner - 1);
+		}
+	}
+
+	/* Spin on the lock value in the spinlock_t */
 	count = spin_retry;
 	while (1) {
-		owner = arch_load_niai4(&lp->lock);
-		/* Try to get the lock if it is free. */
+		old = READ_ONCE(lp->lock);
+		owner = old & _Q_LOCK_CPU_MASK;
 		if (!owner) {
-			if (arch_cmpxchg_niai8(&lp->lock, 0, cpu))
-				return;
+			tail_id = old & _Q_TAIL_MASK;
+			new = ((tail_id != node_id) ? tail_id : 0) | lockval;
+			if (__atomic_cmpxchg_bool(&lp->lock, old, new))
+				/* Got the lock */
+				break;
 			continue;
 		}
 		if (count-- >= 0)
 			continue;
 		count = spin_retry;
-		/*
-		 * For multiple layers of hypervisors, e.g. z/VM + LPAR
-		 * yield the CPU unconditionally. For LPAR rely on the
-		 * sense running status.
-		 */
 		if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(owner - 1))
 			smp_yield_cpu(owner - 1);
 	}
+
+	/* Pass lock_spin job to next CPU in the queue */
+	if (node_id && tail_id != node_id) {
+		/* Wait until the next CPU has set up the 'next' pointer */
+		while ((next = READ_ONCE(node->next)) == NULL)
+			;
+		next->prev = NULL;
+	}
+
+ out:
+	S390_lowcore.spinlock_index--;
 }
-EXPORT_SYMBOL(arch_spin_lock_wait);
 
-void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
+static inline void arch_spin_lock_classic(arch_spinlock_t *lp)
 {
-	int cpu = SPINLOCK_LOCKVAL;
-	int owner, count;
+	int lockval, old, new, owner, count;
 
-	local_irq_restore(flags);
+	lockval = SPINLOCK_LOCKVAL;	/* cpu + 1 */
 
 	/* Pass the virtual CPU to the lock holder if it is not running */
-	owner = arch_load_niai4(&lp->lock);
+	owner = arch_spin_yield_target(ACCESS_ONCE(lp->lock), NULL);
 	if (owner && arch_vcpu_is_preempted(owner - 1))
 		smp_yield_cpu(owner - 1);
 
 	count = spin_retry;
 	while (1) {
-		owner = arch_load_niai4(&lp->lock);
+		old = arch_load_niai4(&lp->lock);
+		owner = old & _Q_LOCK_CPU_MASK;
 		/* Try to get the lock if it is free. */
 		if (!owner) {
-			local_irq_disable();
-			if (arch_cmpxchg_niai8(&lp->lock, 0, cpu))
-				return;
-			local_irq_restore(flags);
+			new = (old & _Q_TAIL_MASK) | lockval;
+			if (arch_cmpxchg_niai8(&lp->lock, old, new))
+				/* Got the lock */
+			       return;
 			continue;
 		}
 		if (count-- >= 0)
 			continue;
 		count = spin_retry;
-		/*
-		 * For multiple layers of hypervisors, e.g. z/VM + LPAR
-		 * yield the CPU unconditionally. For LPAR rely on the
-		 * sense running status.
-		 */
 		if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(owner - 1))
 			smp_yield_cpu(owner - 1);
 	}
 }
-EXPORT_SYMBOL(arch_spin_lock_wait_flags);
+
+void arch_spin_lock_wait(arch_spinlock_t *lp)
+{
+	/* Use classic spinlocks + niai if the steal time is >= 10% */
+	if (test_cpu_flag(CIF_DEDICATED_CPU))
+		arch_spin_lock_queued(lp);
+	else
+		arch_spin_lock_classic(lp);
+}
+EXPORT_SYMBOL(arch_spin_lock_wait);
 
 int arch_spin_trylock_retry(arch_spinlock_t *lp)
 {
@@ -270,3 +391,16 @@ void arch_lock_relax(int cpu)
 	smp_yield_cpu(cpu - 1);
 }
 EXPORT_SYMBOL(arch_lock_relax);
+
+void arch_spin_relax(arch_spinlock_t *lp)
+{
+	int cpu;
+
+	cpu = READ_ONCE(lp->lock) & _Q_LOCK_CPU_MASK;
+	if (!cpu)
+		return;
+	if (MACHINE_IS_LPAR && !arch_vcpu_is_preempted(cpu - 1))
+		return;
+	smp_yield_cpu(cpu - 1);
+}
+EXPORT_SYMBOL(arch_spin_relax);