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
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
#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)
{
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
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
* (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(¶virt_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
#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>
kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
}
-
-#ifdef CONFIG_QUEUED_SPINLOCKS
-
#include <asm/qspinlock.h>
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.
*/
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)
#include <asm/paravirt.h>
-#ifdef CONFIG_QUEUED_SPINLOCKS
__visible void __native_queued_spin_unlock(struct qspinlock *lock)
{
native_queued_spin_unlock(lock);
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);
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
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;
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
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;
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)
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();
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
}
/*
}
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 */
projects / GitHub / LineageOS / android_kernel_motorola_exynos9610.git / commitdiff