[deliverable/linux.git] / arch / x86 / xen / spinlock.c

/*
 * Split spinlock implementation out into its own file, so it can be
 * compiled in a FTRACE-compatible way.
 */
#include <linux/kernel_stat.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/log2.h>
#include <linux/gfp.h>
#include <linux/slab.h>

#include <asm/paravirt.h>

#include <xen/interface/xen.h>
#include <xen/events.h>

#include "xen-ops.h"
#include "debugfs.h"

#ifdef CONFIG_XEN_DEBUG_FS
static struct xen_spinlock_stats
{
	u64 taken;
	u32 taken_slow;
	u32 taken_slow_nested;
	u32 taken_slow_pickup;
	u32 taken_slow_spurious;
	u32 taken_slow_irqenable;

	u64 released;
	u32 released_slow;
	u32 released_slow_kicked;

#define HISTO_BUCKETS	30
	u32 histo_spin_total[HISTO_BUCKETS+1];
	u32 histo_spin_spinning[HISTO_BUCKETS+1];
	u32 histo_spin_blocked[HISTO_BUCKETS+1];

	u64 time_total;
	u64 time_spinning;
	u64 time_blocked;
} spinlock_stats;

static u8 zero_stats;

static unsigned lock_timeout = 1 << 10;
#define TIMEOUT lock_timeout

static inline void check_zero(void)
{
	if (unlikely(zero_stats)) {
		memset(&spinlock_stats, 0, sizeof(spinlock_stats));
		zero_stats = 0;
	}
}

#define ADD_STATS(elem, val)			\
	do { check_zero(); spinlock_stats.elem += (val); } while(0)

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_spinning(u64 start)
{
	u32 delta = xen_clocksource_read() - start;

	__spin_time_accum(delta, spinlock_stats.histo_spin_spinning);
	spinlock_stats.time_spinning += delta;
}

static inline void spin_time_accum_total(u64 start)
{
	u32 delta = xen_clocksource_read() - start;

	__spin_time_accum(delta, spinlock_stats.histo_spin_total);
	spinlock_stats.time_total += delta;
}

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 */
#define TIMEOUT			(1 << 10)
#define ADD_STATS(elem, val)	do { (void)(val); } while(0)

static inline u64 spin_time_start(void)
{
	return 0;
}

static inline void spin_time_accum_total(u64 start)
{
}
static inline void spin_time_accum_spinning(u64 start)
{
}
static inline void spin_time_accum_blocked(u64 start)
{
}
#endif  /* CONFIG_XEN_DEBUG_FS */

/*
 * Size struct xen_spinlock so it's the same as arch_spinlock_t.
 */
#if NR_CPUS < 256
typedef u8 xen_spinners_t;
# define inc_spinners(xl) \
	asm(LOCK_PREFIX " incb %0" : "+m" ((xl)->spinners) : : "memory");
# define dec_spinners(xl) \
	asm(LOCK_PREFIX " decb %0" : "+m" ((xl)->spinners) : : "memory");
#else
typedef u16 xen_spinners_t;
# define inc_spinners(xl) \
	asm(LOCK_PREFIX " incw %0" : "+m" ((xl)->spinners) : : "memory");
# define dec_spinners(xl) \
	asm(LOCK_PREFIX " decw %0" : "+m" ((xl)->spinners) : : "memory");
#endif

struct xen_spinlock {
	unsigned char lock;		/* 0 -> free; 1 -> locked */
	xen_spinners_t spinners;	/* count of waiting cpus */
};

static int xen_spin_is_locked(struct arch_spinlock *lock)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;

	return xl->lock != 0;
}

static int xen_spin_is_contended(struct arch_spinlock *lock)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;

	/* Not strictly true; this is only the count of contended
	   lock-takers entering the slow path. */
	return xl->spinners != 0;
}

static int xen_spin_trylock(struct arch_spinlock *lock)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;
	u8 old = 1;

	asm("xchgb %b0,%1"
	    : "+q" (old), "+m" (xl->lock) : : "memory");

	return old == 0;
}

static DEFINE_PER_CPU(char *, irq_name);
static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
static DEFINE_PER_CPU(struct xen_spinlock *, lock_spinners);

/*
 * Mark a cpu as interested in a lock.  Returns the CPU's previous
 * lock of interest, in case we got preempted by an interrupt.
 */
static inline struct xen_spinlock *spinning_lock(struct xen_spinlock *xl)
{
	struct xen_spinlock *prev;

	prev = __this_cpu_read(lock_spinners);
	__this_cpu_write(lock_spinners, xl);

	wmb();			/* set lock of interest before count */

	inc_spinners(xl);

	return prev;
}

/*
 * Mark a cpu as no longer interested in a lock.  Restores previous
 * lock of interest (NULL for none).
 */
static inline void unspinning_lock(struct xen_spinlock *xl, struct xen_spinlock *prev)
{
	dec_spinners(xl);
	wmb();			/* decrement count before restoring lock */
	__this_cpu_write(lock_spinners, prev);
}

static noinline int xen_spin_lock_slow(struct arch_spinlock *lock, bool irq_enable)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;
	struct xen_spinlock *prev;
	int irq = __this_cpu_read(lock_kicker_irq);
	int ret;
	u64 start;

	/* If kicker interrupts not initialized yet, just spin */
	if (irq == -1)
		return 0;

	start = spin_time_start();

	/* announce we're spinning */
	prev = spinning_lock(xl);

	ADD_STATS(taken_slow, 1);
	ADD_STATS(taken_slow_nested, prev != NULL);

	do {
		unsigned long flags;

		/* clear pending */
		xen_clear_irq_pending(irq);

		/* check again make sure it didn't become free while
		   we weren't looking  */
		ret = xen_spin_trylock(lock);
		if (ret) {
			ADD_STATS(taken_slow_pickup, 1);

			/*
			 * If we interrupted another spinlock while it
			 * was blocking, make sure it doesn't block
			 * without rechecking the lock.
			 */
			if (prev != NULL)
				xen_set_irq_pending(irq);
			goto out;
		}

		flags = arch_local_save_flags();
		if (irq_enable) {
			ADD_STATS(taken_slow_irqenable, 1);
			raw_local_irq_enable();
		}

		/*
		 * Block until irq becomes pending.  If we're
		 * interrupted at this point (after the trylock but
		 * before entering the block), then the nested lock
		 * handler guarantees that the irq will be left
		 * pending if there's any chance the lock became free;
		 * xen_poll_irq() returns immediately if the irq is
		 * pending.
		 */
		xen_poll_irq(irq);

		raw_local_irq_restore(flags);

		ADD_STATS(taken_slow_spurious, !xen_test_irq_pending(irq));
	} while (!xen_test_irq_pending(irq)); /* check for spurious wakeups */

	kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));

out:
	unspinning_lock(xl, prev);
	spin_time_accum_blocked(start);

	return ret;
}

static inline void __xen_spin_lock(struct arch_spinlock *lock, bool irq_enable)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;
	unsigned timeout;
	u8 oldval;
	u64 start_spin;

	ADD_STATS(taken, 1);

	start_spin = spin_time_start();

	do {
		u64 start_spin_fast = spin_time_start();

		timeout = TIMEOUT;

		asm("1: xchgb %1,%0\n"
		    "   testb %1,%1\n"
		    "   jz 3f\n"
		    "2: rep;nop\n"
		    "   cmpb $0,%0\n"
		    "   je 1b\n"
		    "   dec %2\n"
		    "   jnz 2b\n"
		    "3:\n"
		    : "+m" (xl->lock), "=q" (oldval), "+r" (timeout)
		    : "1" (1)
		    : "memory");

		spin_time_accum_spinning(start_spin_fast);

	} while (unlikely(oldval != 0 &&
			  (TIMEOUT == ~0 || !xen_spin_lock_slow(lock, irq_enable))));

	spin_time_accum_total(start_spin);
}

static void xen_spin_lock(struct arch_spinlock *lock)
{
	__xen_spin_lock(lock, false);
}

static void xen_spin_lock_flags(struct arch_spinlock *lock, unsigned long flags)
{
	__xen_spin_lock(lock, !raw_irqs_disabled_flags(flags));
}

static noinline void xen_spin_unlock_slow(struct xen_spinlock *xl)
{
	int cpu;

	ADD_STATS(released_slow, 1);

	for_each_online_cpu(cpu) {
		/* XXX should mix up next cpu selection */
		if (per_cpu(lock_spinners, cpu) == xl) {
			ADD_STATS(released_slow_kicked, 1);
			xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
		}
	}
}

static void xen_spin_unlock(struct arch_spinlock *lock)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;

	ADD_STATS(released, 1);

	smp_wmb();		/* make sure no writes get moved after unlock */
	xl->lock = 0;		/* release lock */

	/*
	 * Make sure unlock happens before checking for waiting
	 * spinners.  We need a strong barrier to enforce the
	 * write-read ordering to different memory locations, as the
	 * CPU makes no implied guarantees about their ordering.
	 */
	mb();

	if (unlikely(xl->spinners))
		xen_spin_unlock_slow(xl);
}

static irqreturn_t dummy_handler(int irq, void *dev_id)
{
	BUG();
	return IRQ_HANDLED;
}

void xen_init_lock_cpu(int cpu)
{
	int irq;
	char *name;

	WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
	     cpu, per_cpu(lock_kicker_irq, cpu));

	/*
	 * See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23
	 * (xen: disable PV spinlocks on HVM)
	 */
	if (xen_hvm_domain())
		return;

	name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
	irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
				     cpu,
				     dummy_handler,
				     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
				     name,
				     NULL);

	if (irq >= 0) {
		disable_irq(irq); /* make sure it's never delivered */
		per_cpu(lock_kicker_irq, cpu) = irq;
		per_cpu(irq_name, cpu) = name;
	}

	printk("cpu %d spinlock event irq %d\n", cpu, irq);
}

void xen_uninit_lock_cpu(int cpu)
{
	/*
	 * See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23
	 * (xen: disable PV spinlocks on HVM)
	 */
	if (xen_hvm_domain())
		return;

	unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
	per_cpu(lock_kicker_irq, cpu) = -1;
	kfree(per_cpu(irq_name, cpu));
	per_cpu(irq_name, cpu) = NULL;
}

void __init xen_init_spinlocks(void)
{
	/*
	 * See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23
	 * (xen: disable PV spinlocks on HVM)
	 */
	if (xen_hvm_domain())
		return;

	BUILD_BUG_ON(sizeof(struct xen_spinlock) > sizeof(arch_spinlock_t));

	pv_lock_ops.spin_is_locked = xen_spin_is_locked;
	pv_lock_ops.spin_is_contended = xen_spin_is_contended;
	pv_lock_ops.spin_lock = xen_spin_lock;
	pv_lock_ops.spin_lock_flags = xen_spin_lock_flags;
	pv_lock_ops.spin_trylock = xen_spin_trylock;
	pv_lock_ops.spin_unlock = xen_spin_unlock;
}

#ifdef CONFIG_XEN_DEBUG_FS

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;

	d_spin_debug = debugfs_create_dir("spinlocks", d_xen);

	debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);

	debugfs_create_u32("timeout", 0644, d_spin_debug, &lock_timeout);

	debugfs_create_u64("taken", 0444, d_spin_debug, &spinlock_stats.taken);
	debugfs_create_u32("taken_slow", 0444, d_spin_debug,
			   &spinlock_stats.taken_slow);
	debugfs_create_u32("taken_slow_nested", 0444, d_spin_debug,
			   &spinlock_stats.taken_slow_nested);
	debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
			   &spinlock_stats.taken_slow_pickup);
	debugfs_create_u32("taken_slow_spurious", 0444, d_spin_debug,
			   &spinlock_stats.taken_slow_spurious);
	debugfs_create_u32("taken_slow_irqenable", 0444, d_spin_debug,
			   &spinlock_stats.taken_slow_irqenable);

	debugfs_create_u64("released", 0444, d_spin_debug, &spinlock_stats.released);
	debugfs_create_u32("released_slow", 0444, d_spin_debug,
			   &spinlock_stats.released_slow);
	debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
			   &spinlock_stats.released_slow_kicked);

	debugfs_create_u64("time_spinning", 0444, d_spin_debug,
			   &spinlock_stats.time_spinning);
	debugfs_create_u64("time_blocked", 0444, d_spin_debug,
			   &spinlock_stats.time_blocked);
	debugfs_create_u64("time_total", 0444, d_spin_debug,
			   &spinlock_stats.time_total);

	debugfs_create_u32_array("histo_total", 0444, d_spin_debug,
				spinlock_stats.histo_spin_total, HISTO_BUCKETS + 1);
	debugfs_create_u32_array("histo_spinning", 0444, d_spin_debug,
				spinlock_stats.histo_spin_spinning, HISTO_BUCKETS + 1);
	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 */
Commit	Line	Data
d5de8841 JF	1	/*
	2	* Split spinlock implementation out into its own file, so it can be
	3	* compiled in a FTRACE-compatible way.
	4	*/
	5	#include <linux/kernel_stat.h>
	6	#include <linux/spinlock.h>
994025ca JF	7	#include <linux/debugfs.h>
994025ca JF	8	#include <linux/log2.h>
5a0e3ad6	9	#include <linux/gfp.h>
354e7b76	10	#include <linux/slab.h>
d5de8841 JF	11
	12	#include <asm/paravirt.h>
	13
	14	#include <xen/interface/xen.h>
	15	#include <xen/events.h>
	16
	17	#include "xen-ops.h"
994025ca JF	18	#include "debugfs.h"
	19
	20	#ifdef CONFIG_XEN_DEBUG_FS
	21	static struct xen_spinlock_stats
	22	{
	23	u64 taken;
	24	u32 taken_slow;
	25	u32 taken_slow_nested;
	26	u32 taken_slow_pickup;
	27	u32 taken_slow_spurious;
1e696f63	28	u32 taken_slow_irqenable;
994025ca JF	29
	30	u64 released;
	31	u32 released_slow;
	32	u32 released_slow_kicked;
	33
f8eca41f JF	34	#define HISTO_BUCKETS 30
	35	u32 histo_spin_total[HISTO_BUCKETS+1];
	36	u32 histo_spin_spinning[HISTO_BUCKETS+1];
	37	u32 histo_spin_blocked[HISTO_BUCKETS+1];
	38
	39	u64 time_total;
	40	u64 time_spinning;
	41	u64 time_blocked;
994025ca JF	42	} spinlock_stats;
	43
	44	static u8 zero_stats;
	45
	46	static unsigned lock_timeout = 1 << 10;
	47	#define TIMEOUT lock_timeout
	48
	49	static inline void check_zero(void)
	50	{
	51	if (unlikely(zero_stats)) {
	52	memset(&spinlock_stats, 0, sizeof(spinlock_stats));
	53	zero_stats = 0;
	54	}
	55	}
	56
	57	#define ADD_STATS(elem, val) \
	58	do { check_zero(); spinlock_stats.elem += (val); } while(0)
	59
	60	static inline u64 spin_time_start(void)
	61	{
	62	return xen_clocksource_read();
	63	}
	64
	65	static void __spin_time_accum(u64 delta, u32 *array)
	66	{
	67	unsigned index = ilog2(delta);
	68
	69	check_zero();
	70
	71	if (index < HISTO_BUCKETS)
	72	array[index]++;
	73	else
	74	array[HISTO_BUCKETS]++;
	75	}
	76
f8eca41f JF	77	static inline void spin_time_accum_spinning(u64 start)
	78	{
	79	u32 delta = xen_clocksource_read() - start;
	80
	81	__spin_time_accum(delta, spinlock_stats.histo_spin_spinning);
	82	spinlock_stats.time_spinning += delta;
	83	}
	84
	85	static inline void spin_time_accum_total(u64 start)
994025ca JF	86	{
	87	u32 delta = xen_clocksource_read() - start;
	88
f8eca41f JF	89	__spin_time_accum(delta, spinlock_stats.histo_spin_total);
f8eca41f JF	90	spinlock_stats.time_total += delta;
994025ca JF	91	}
994025ca JF	92
f8eca41f	93	static inline void spin_time_accum_blocked(u64 start)
994025ca JF	94	{
	95	u32 delta = xen_clocksource_read() - start;
	96
f8eca41f JF	97	__spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
f8eca41f JF	98	spinlock_stats.time_blocked += delta;
994025ca JF	99	}
	100	#else /* !CONFIG_XEN_DEBUG_FS */
	101	#define TIMEOUT (1 << 10)
	102	#define ADD_STATS(elem, val) do { (void)(val); } while(0)
	103
	104	static inline u64 spin_time_start(void)
	105	{
	106	return 0;
	107	}
	108
f8eca41f JF	109	static inline void spin_time_accum_total(u64 start)
	110	{
	111	}
	112	static inline void spin_time_accum_spinning(u64 start)
994025ca JF	113	{
994025ca JF	114	}
f8eca41f	115	static inline void spin_time_accum_blocked(u64 start)
994025ca JF	116	{
	117	}
	118	#endif /* CONFIG_XEN_DEBUG_FS */
d5de8841	119
7a7546b3 DV	120	/*
	121	* Size struct xen_spinlock so it's the same as arch_spinlock_t.
	122	*/
	123	#if NR_CPUS < 256
	124	typedef u8 xen_spinners_t;
	125	# define inc_spinners(xl) \
	126	asm(LOCK_PREFIX " incb %0" : "+m" ((xl)->spinners) : : "memory");
	127	# define dec_spinners(xl) \
	128	asm(LOCK_PREFIX " decb %0" : "+m" ((xl)->spinners) : : "memory");
	129	#else
	130	typedef u16 xen_spinners_t;
	131	# define inc_spinners(xl) \
	132	asm(LOCK_PREFIX " incw %0" : "+m" ((xl)->spinners) : : "memory");
	133	# define dec_spinners(xl) \
	134	asm(LOCK_PREFIX " decw %0" : "+m" ((xl)->spinners) : : "memory");
	135	#endif
	136
d5de8841 JF	137	struct xen_spinlock {
d5de8841 JF	138	unsigned char lock; /* 0 -> free; 1 -> locked */
7a7546b3	139	xen_spinners_t spinners; /* count of waiting cpus */
d5de8841 JF	140	};
d5de8841 JF	141
445c8951	142	static int xen_spin_is_locked(struct arch_spinlock *lock)
d5de8841 JF	143	{
	144	struct xen_spinlock xl = (struct xen_spinlock )lock;
	145
	146	return xl->lock != 0;
	147	}
	148
445c8951	149	static int xen_spin_is_contended(struct arch_spinlock *lock)
d5de8841 JF	150	{
	151	struct xen_spinlock xl = (struct xen_spinlock )lock;
	152
	153	/* Not strictly true; this is only the count of contended
	154	lock-takers entering the slow path. */
	155	return xl->spinners != 0;
	156	}
	157
445c8951	158	static int xen_spin_trylock(struct arch_spinlock *lock)
d5de8841 JF	159	{
	160	struct xen_spinlock xl = (struct xen_spinlock )lock;
	161	u8 old = 1;
	162
	163	asm("xchgb %b0,%1"
	164	: "+q" (old), "+m" (xl->lock) : : "memory");
	165
	166	return old == 0;
	167	}
	168
354e7b76	169	static DEFINE_PER_CPU(char *, irq_name);
d5de8841 JF	170	static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
	171	static DEFINE_PER_CPU(struct xen_spinlock *, lock_spinners);
	172
168d2f46 JF	173	/*
	174	* Mark a cpu as interested in a lock. Returns the CPU's previous
	175	* lock of interest, in case we got preempted by an interrupt.
	176	*/
	177	static inline struct xen_spinlock spinning_lock(struct xen_spinlock xl)
d5de8841	178	{
168d2f46 JF	179	struct xen_spinlock *prev;
168d2f46 JF	180
780f36d8 CL	181	prev = __this_cpu_read(lock_spinners);
780f36d8 CL	182	__this_cpu_write(lock_spinners, xl);
168d2f46	183
d5de8841	184	wmb(); /* set lock of interest before count */
168d2f46	185
7a7546b3	186	inc_spinners(xl);
168d2f46 JF	187
168d2f46 JF	188	return prev;
d5de8841 JF	189	}
d5de8841 JF	190
168d2f46 JF	191	/*
	192	* Mark a cpu as no longer interested in a lock. Restores previous
	193	* lock of interest (NULL for none).
	194	*/
	195	static inline void unspinning_lock(struct xen_spinlock xl, struct xen_spinlock prev)
d5de8841	196	{
7a7546b3	197	dec_spinners(xl);
168d2f46	198	wmb(); /* decrement count before restoring lock */
780f36d8	199	__this_cpu_write(lock_spinners, prev);
d5de8841 JF	200	}
d5de8841 JF	201
445c8951	202	static noinline int xen_spin_lock_slow(struct arch_spinlock *lock, bool irq_enable)
d5de8841 JF	203	{
d5de8841 JF	204	struct xen_spinlock xl = (struct xen_spinlock )lock;
168d2f46	205	struct xen_spinlock *prev;
780f36d8	206	int irq = __this_cpu_read(lock_kicker_irq);
d5de8841	207	int ret;
f8eca41f	208	u64 start;
d5de8841 JF	209
	210	/* If kicker interrupts not initialized yet, just spin */
	211	if (irq == -1)
	212	return 0;
	213
f8eca41f JF	214	start = spin_time_start();
f8eca41f JF	215
d5de8841	216	/* announce we're spinning */
168d2f46	217	prev = spinning_lock(xl);
d5de8841	218
994025ca JF	219	ADD_STATS(taken_slow, 1);
	220	ADD_STATS(taken_slow_nested, prev != NULL);
	221
168d2f46	222	do {
4d576b57 JF	223	unsigned long flags;
4d576b57 JF	224
168d2f46 JF	225	/* clear pending */
	226	xen_clear_irq_pending(irq);
	227
	228	/* check again make sure it didn't become free while
	229	we weren't looking */
	230	ret = xen_spin_trylock(lock);
	231	if (ret) {
994025ca JF	232	ADD_STATS(taken_slow_pickup, 1);
994025ca JF	233
168d2f46 JF	234	/*
	235	* If we interrupted another spinlock while it
	236	* was blocking, make sure it doesn't block
	237	* without rechecking the lock.
	238	*/
	239	if (prev != NULL)
	240	xen_set_irq_pending(irq);
	241	goto out;
	242	}
d5de8841	243
df9ee292	244	flags = arch_local_save_flags();
4d576b57 JF	245	if (irq_enable) {
	246	ADD_STATS(taken_slow_irqenable, 1);
	247	raw_local_irq_enable();
	248	}
	249
168d2f46 JF	250	/*
	251	* Block until irq becomes pending. If we're
	252	* interrupted at this point (after the trylock but
	253	* before entering the block), then the nested lock
	254	* handler guarantees that the irq will be left
	255	* pending if there's any chance the lock became free;
	256	* xen_poll_irq() returns immediately if the irq is
	257	* pending.
	258	*/
	259	xen_poll_irq(irq);
4d576b57 JF	260
	261	raw_local_irq_restore(flags);
	262
994025ca	263	ADD_STATS(taken_slow_spurious, !xen_test_irq_pending(irq));
168d2f46	264	} while (!xen_test_irq_pending(irq)); /* check for spurious wakeups */
d5de8841	265
d6c88a50	266	kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));
d5de8841 JF	267
d5de8841 JF	268	out:
168d2f46	269	unspinning_lock(xl, prev);
f8eca41f JF	270	spin_time_accum_blocked(start);
f8eca41f JF	271
d5de8841 JF	272	return ret;
	273	}
	274
445c8951	275	static inline void __xen_spin_lock(struct arch_spinlock *lock, bool irq_enable)
d5de8841 JF	276	{
d5de8841 JF	277	struct xen_spinlock xl = (struct xen_spinlock )lock;
994025ca	278	unsigned timeout;
d5de8841	279	u8 oldval;
994025ca JF	280	u64 start_spin;
	281
	282	ADD_STATS(taken, 1);
	283
	284	start_spin = spin_time_start();
d5de8841 JF	285
d5de8841 JF	286	do {
994025ca JF	287	u64 start_spin_fast = spin_time_start();
	288
	289	timeout = TIMEOUT;
d5de8841 JF	290
	291	asm("1: xchgb %1,%0\n"
	292	" testb %1,%1\n"
	293	" jz 3f\n"
	294	"2: rep;nop\n"
	295	" cmpb $0,%0\n"
	296	" je 1b\n"
	297	" dec %2\n"
	298	" jnz 2b\n"
	299	"3:\n"
	300	: "+m" (xl->lock), "=q" (oldval), "+r" (timeout)
	301	: "1" (1)
	302	: "memory");
	303
f8eca41f	304	spin_time_accum_spinning(start_spin_fast);
1e696f63 JF	305
	306	} while (unlikely(oldval != 0 &&
	307	(TIMEOUT == ~0 \|\| !xen_spin_lock_slow(lock, irq_enable))));
994025ca	308
f8eca41f	309	spin_time_accum_total(start_spin);
d5de8841 JF	310	}
d5de8841 JF	311
445c8951	312	static void xen_spin_lock(struct arch_spinlock *lock)
1e696f63 JF	313	{
	314	__xen_spin_lock(lock, false);
	315	}
	316
445c8951	317	static void xen_spin_lock_flags(struct arch_spinlock *lock, unsigned long flags)
1e696f63 JF	318	{
	319	__xen_spin_lock(lock, !raw_irqs_disabled_flags(flags));
	320	}
	321
d5de8841 JF	322	static noinline void xen_spin_unlock_slow(struct xen_spinlock *xl)
	323	{
	324	int cpu;
	325
994025ca JF	326	ADD_STATS(released_slow, 1);
994025ca JF	327
d5de8841 JF	328	for_each_online_cpu(cpu) {
	329	/* XXX should mix up next cpu selection */
	330	if (per_cpu(lock_spinners, cpu) == xl) {
994025ca	331	ADD_STATS(released_slow_kicked, 1);
d5de8841	332	xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
d5de8841 JF	333	}
	334	}
	335	}
	336
445c8951	337	static void xen_spin_unlock(struct arch_spinlock *lock)
d5de8841 JF	338	{
	339	struct xen_spinlock xl = (struct xen_spinlock )lock;
	340
994025ca JF	341	ADD_STATS(released, 1);
994025ca JF	342
d5de8841 JF	343	smp_wmb(); /* make sure no writes get moved after unlock */
	344	xl->lock = 0; /* release lock */
	345
2496afbf YX	346	/*
	347	* Make sure unlock happens before checking for waiting
	348	* spinners. We need a strong barrier to enforce the
	349	* write-read ordering to different memory locations, as the
	350	* CPU makes no implied guarantees about their ordering.
	351	*/
	352	mb();
d5de8841 JF	353
	354	if (unlikely(xl->spinners))
	355	xen_spin_unlock_slow(xl);
	356	}
	357
	358	static irqreturn_t dummy_handler(int irq, void *dev_id)
	359	{
	360	BUG();
	361	return IRQ_HANDLED;
	362	}
	363
148f9bb8	364	void xen_init_lock_cpu(int cpu)
d5de8841 JF	365	{
d5de8841 JF	366	int irq;
354e7b76	367	char *name;
d5de8841	368
cb91f8f4	369	WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
cb9c6f15 KRW	370	cpu, per_cpu(lock_kicker_irq, cpu));
cb9c6f15 KRW	371
70dd4998 KRW	372	/*
	373	* See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23
	374	* (xen: disable PV spinlocks on HVM)
	375	*/
	376	if (xen_hvm_domain())
	377	return;
	378
d5de8841 JF	379	name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
	380	irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
	381	cpu,
	382	dummy_handler,
	383	IRQF_DISABLED\|IRQF_PERCPU\|IRQF_NOBALANCING,
	384	name,
	385	NULL);
	386
	387	if (irq >= 0) {
	388	disable_irq(irq); /* make sure it's never delivered */
	389	per_cpu(lock_kicker_irq, cpu) = irq;
354e7b76	390	per_cpu(irq_name, cpu) = name;
d5de8841 JF	391	}
	392
	393	printk("cpu %d spinlock event irq %d\n", cpu, irq);
	394	}
	395
d68d82af AN	396	void xen_uninit_lock_cpu(int cpu)
d68d82af AN	397	{
70dd4998 KRW	398	/*
	399	* See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23
	400	* (xen: disable PV spinlocks on HVM)
	401	*/
	402	if (xen_hvm_domain())
	403	return;
	404
d68d82af	405	unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
cb9c6f15	406	per_cpu(lock_kicker_irq, cpu) = -1;
354e7b76 KRW	407	kfree(per_cpu(irq_name, cpu));
354e7b76 KRW	408	per_cpu(irq_name, cpu) = NULL;
d68d82af AN	409	}
d68d82af AN	410
d5de8841 JF	411	void __init xen_init_spinlocks(void)
d5de8841 JF	412	{
70dd4998 KRW	413	/*
	414	* See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23
	415	* (xen: disable PV spinlocks on HVM)
	416	*/
	417	if (xen_hvm_domain())
	418	return;
	419
7a7546b3 DV	420	BUILD_BUG_ON(sizeof(struct xen_spinlock) > sizeof(arch_spinlock_t));
7a7546b3 DV	421
d5de8841 JF	422	pv_lock_ops.spin_is_locked = xen_spin_is_locked;
	423	pv_lock_ops.spin_is_contended = xen_spin_is_contended;
	424	pv_lock_ops.spin_lock = xen_spin_lock;
1e696f63	425	pv_lock_ops.spin_lock_flags = xen_spin_lock_flags;
d5de8841 JF	426	pv_lock_ops.spin_trylock = xen_spin_trylock;
	427	pv_lock_ops.spin_unlock = xen_spin_unlock;
	428	}
994025ca JF	429
	430	#ifdef CONFIG_XEN_DEBUG_FS
	431
	432	static struct dentry *d_spin_debug;
	433
	434	static int __init xen_spinlock_debugfs(void)
	435	{
	436	struct dentry *d_xen = xen_init_debugfs();
	437
	438	if (d_xen == NULL)
	439	return -ENOMEM;
	440
	441	d_spin_debug = debugfs_create_dir("spinlocks", d_xen);
	442
	443	debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
	444
	445	debugfs_create_u32("timeout", 0644, d_spin_debug, &lock_timeout);
	446
	447	debugfs_create_u64("taken", 0444, d_spin_debug, &spinlock_stats.taken);
	448	debugfs_create_u32("taken_slow", 0444, d_spin_debug,
	449	&spinlock_stats.taken_slow);
	450	debugfs_create_u32("taken_slow_nested", 0444, d_spin_debug,
	451	&spinlock_stats.taken_slow_nested);
	452	debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
	453	&spinlock_stats.taken_slow_pickup);
	454	debugfs_create_u32("taken_slow_spurious", 0444, d_spin_debug,
	455	&spinlock_stats.taken_slow_spurious);
1e696f63 JF	456	debugfs_create_u32("taken_slow_irqenable", 0444, d_spin_debug,
1e696f63 JF	457	&spinlock_stats.taken_slow_irqenable);
994025ca JF	458
	459	debugfs_create_u64("released", 0444, d_spin_debug, &spinlock_stats.released);
	460	debugfs_create_u32("released_slow", 0444, d_spin_debug,
	461	&spinlock_stats.released_slow);
	462	debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
	463	&spinlock_stats.released_slow_kicked);
	464
	465	debugfs_create_u64("time_spinning", 0444, d_spin_debug,
f8eca41f JF	466	&spinlock_stats.time_spinning);
	467	debugfs_create_u64("time_blocked", 0444, d_spin_debug,
	468	&spinlock_stats.time_blocked);
994025ca	469	debugfs_create_u64("time_total", 0444, d_spin_debug,
f8eca41f	470	&spinlock_stats.time_total);
994025ca	471
9fe2a701 SV	472	debugfs_create_u32_array("histo_total", 0444, d_spin_debug,
	473	spinlock_stats.histo_spin_total, HISTO_BUCKETS + 1);
	474	debugfs_create_u32_array("histo_spinning", 0444, d_spin_debug,
	475	spinlock_stats.histo_spin_spinning, HISTO_BUCKETS + 1);
	476	debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
	477	spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
994025ca JF	478
	479	return 0;
	480	}
	481	fs_initcall(xen_spinlock_debugfs);
	482
	483	#endif /* CONFIG_XEN_DEBUG_FS */