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.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra
Ingo Molnar
Родитель
0b429e18c2
Коммит
cfd8983f03
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@ -705,7 +705,6 @@ config PARAVIRT_DEBUG
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config PARAVIRT_SPINLOCKS
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bool "Paravirtualization layer for spinlocks"
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depends on PARAVIRT && SMP
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select UNINLINE_SPIN_UNLOCK if !QUEUED_SPINLOCKS
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---help---
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Paravirtualized spinlocks allow a pvops backend to replace the
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spinlock implementation with something virtualization-friendly
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@ -718,7 +717,7 @@ config PARAVIRT_SPINLOCKS
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config QUEUED_LOCK_STAT
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bool "Paravirt queued spinlock statistics"
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depends on PARAVIRT_SPINLOCKS && DEBUG_FS && QUEUED_SPINLOCKS
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depends on PARAVIRT_SPINLOCKS && DEBUG_FS
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---help---
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Enable the collection of statistical data on the slowpath
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behavior of paravirtualized queued spinlocks and report
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@ -661,8 +661,6 @@ static inline void __set_fixmap(unsigned /* enum fixed_addresses */ idx,
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#if defined(CONFIG_SMP) && defined(CONFIG_PARAVIRT_SPINLOCKS)
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#ifdef CONFIG_QUEUED_SPINLOCKS
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static __always_inline void pv_queued_spin_lock_slowpath(struct qspinlock *lock,
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u32 val)
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{
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@ -684,22 +682,6 @@ static __always_inline void pv_kick(int cpu)
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PVOP_VCALL1(pv_lock_ops.kick, cpu);
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}
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#else /* !CONFIG_QUEUED_SPINLOCKS */
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static __always_inline void __ticket_lock_spinning(struct arch_spinlock *lock,
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__ticket_t ticket)
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{
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PVOP_VCALLEE2(pv_lock_ops.lock_spinning, lock, ticket);
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}
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static __always_inline void __ticket_unlock_kick(struct arch_spinlock *lock,
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__ticket_t ticket)
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{
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PVOP_VCALL2(pv_lock_ops.unlock_kick, lock, ticket);
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}
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#endif /* CONFIG_QUEUED_SPINLOCKS */
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#endif /* SMP && PARAVIRT_SPINLOCKS */
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#ifdef CONFIG_X86_32
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@ -301,23 +301,16 @@ struct pv_mmu_ops {
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struct arch_spinlock;
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#ifdef CONFIG_SMP
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#include <asm/spinlock_types.h>
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#else
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typedef u16 __ticket_t;
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#endif
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struct qspinlock;
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struct pv_lock_ops {
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#ifdef CONFIG_QUEUED_SPINLOCKS
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void (*queued_spin_lock_slowpath)(struct qspinlock *lock, u32 val);
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struct paravirt_callee_save queued_spin_unlock;
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void (*wait)(u8 *ptr, u8 val);
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void (*kick)(int cpu);
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#else /* !CONFIG_QUEUED_SPINLOCKS */
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struct paravirt_callee_save lock_spinning;
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void (*unlock_kick)(struct arch_spinlock *lock, __ticket_t ticket);
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#endif /* !CONFIG_QUEUED_SPINLOCKS */
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};
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/* This contains all the paravirt structures: we get a convenient
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@ -20,187 +20,13 @@
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* (the type definitions are in asm/spinlock_types.h)
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*/
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#ifdef CONFIG_X86_32
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# define LOCK_PTR_REG "a"
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#else
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# define LOCK_PTR_REG "D"
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#endif
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#if defined(CONFIG_X86_32) && (defined(CONFIG_X86_PPRO_FENCE))
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/*
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* On PPro SMP, we use a locked operation to unlock
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* (PPro errata 66, 92)
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*/
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# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
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#else
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# define UNLOCK_LOCK_PREFIX
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#endif
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/* How long a lock should spin before we consider blocking */
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#define SPIN_THRESHOLD (1 << 15)
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extern struct static_key paravirt_ticketlocks_enabled;
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static __always_inline bool static_key_false(struct static_key *key);
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#ifdef CONFIG_QUEUED_SPINLOCKS
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#include <asm/qspinlock.h>
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#else
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#ifdef CONFIG_PARAVIRT_SPINLOCKS
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static inline void __ticket_enter_slowpath(arch_spinlock_t *lock)
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{
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set_bit(0, (volatile unsigned long *)&lock->tickets.head);
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}
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#else /* !CONFIG_PARAVIRT_SPINLOCKS */
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static __always_inline void __ticket_lock_spinning(arch_spinlock_t *lock,
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__ticket_t ticket)
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{
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}
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static inline void __ticket_unlock_kick(arch_spinlock_t *lock,
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__ticket_t ticket)
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{
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}
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#endif /* CONFIG_PARAVIRT_SPINLOCKS */
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static inline int __tickets_equal(__ticket_t one, __ticket_t two)
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{
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return !((one ^ two) & ~TICKET_SLOWPATH_FLAG);
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}
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static inline void __ticket_check_and_clear_slowpath(arch_spinlock_t *lock,
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__ticket_t head)
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{
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if (head & TICKET_SLOWPATH_FLAG) {
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arch_spinlock_t old, new;
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old.tickets.head = head;
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new.tickets.head = head & ~TICKET_SLOWPATH_FLAG;
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old.tickets.tail = new.tickets.head + TICKET_LOCK_INC;
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new.tickets.tail = old.tickets.tail;
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/* try to clear slowpath flag when there are no contenders */
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cmpxchg(&lock->head_tail, old.head_tail, new.head_tail);
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}
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}
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static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
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{
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return __tickets_equal(lock.tickets.head, lock.tickets.tail);
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}
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/*
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* Ticket locks are conceptually two parts, one indicating the current head of
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* the queue, and the other indicating the current tail. The lock is acquired
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* by atomically noting the tail and incrementing it by one (thus adding
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* ourself to the queue and noting our position), then waiting until the head
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* becomes equal to the the initial value of the tail.
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*
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* We use an xadd covering *both* parts of the lock, to increment the tail and
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* also load the position of the head, which takes care of memory ordering
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* issues and should be optimal for the uncontended case. Note the tail must be
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* in the high part, because a wide xadd increment of the low part would carry
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* up and contaminate the high part.
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*/
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static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
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{
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register struct __raw_tickets inc = { .tail = TICKET_LOCK_INC };
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inc = xadd(&lock->tickets, inc);
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if (likely(inc.head == inc.tail))
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goto out;
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for (;;) {
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unsigned count = SPIN_THRESHOLD;
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do {
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inc.head = READ_ONCE(lock->tickets.head);
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if (__tickets_equal(inc.head, inc.tail))
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goto clear_slowpath;
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cpu_relax();
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} while (--count);
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__ticket_lock_spinning(lock, inc.tail);
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}
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clear_slowpath:
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__ticket_check_and_clear_slowpath(lock, inc.head);
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out:
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barrier(); /* make sure nothing creeps before the lock is taken */
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}
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static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
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{
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arch_spinlock_t old, new;
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old.tickets = READ_ONCE(lock->tickets);
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if (!__tickets_equal(old.tickets.head, old.tickets.tail))
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return 0;
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new.head_tail = old.head_tail + (TICKET_LOCK_INC << TICKET_SHIFT);
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new.head_tail &= ~TICKET_SLOWPATH_FLAG;
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/* cmpxchg is a full barrier, so nothing can move before it */
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return cmpxchg(&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail;
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}
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static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
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{
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if (TICKET_SLOWPATH_FLAG &&
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static_key_false(¶virt_ticketlocks_enabled)) {
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__ticket_t head;
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BUILD_BUG_ON(((__ticket_t)NR_CPUS) != NR_CPUS);
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head = xadd(&lock->tickets.head, TICKET_LOCK_INC);
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if (unlikely(head & TICKET_SLOWPATH_FLAG)) {
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head &= ~TICKET_SLOWPATH_FLAG;
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__ticket_unlock_kick(lock, (head + TICKET_LOCK_INC));
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}
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} else
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__add(&lock->tickets.head, TICKET_LOCK_INC, UNLOCK_LOCK_PREFIX);
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}
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static inline int arch_spin_is_locked(arch_spinlock_t *lock)
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{
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struct __raw_tickets tmp = READ_ONCE(lock->tickets);
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return !__tickets_equal(tmp.tail, tmp.head);
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}
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static inline int arch_spin_is_contended(arch_spinlock_t *lock)
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{
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struct __raw_tickets tmp = READ_ONCE(lock->tickets);
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tmp.head &= ~TICKET_SLOWPATH_FLAG;
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return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC;
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}
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#define arch_spin_is_contended arch_spin_is_contended
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static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock,
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unsigned long flags)
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{
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arch_spin_lock(lock);
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}
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static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
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{
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__ticket_t head = READ_ONCE(lock->tickets.head);
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for (;;) {
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struct __raw_tickets tmp = READ_ONCE(lock->tickets);
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/*
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* We need to check "unlocked" in a loop, tmp.head == head
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* can be false positive because of overflow.
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*/
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if (__tickets_equal(tmp.head, tmp.tail) ||
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!__tickets_equal(tmp.head, head))
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break;
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cpu_relax();
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}
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}
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#endif /* CONFIG_QUEUED_SPINLOCKS */
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/*
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* Read-write spinlocks, allowing multiple readers
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@ -23,20 +23,7 @@ typedef u32 __ticketpair_t;
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#define TICKET_SHIFT (sizeof(__ticket_t) * 8)
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#ifdef CONFIG_QUEUED_SPINLOCKS
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#include <asm-generic/qspinlock_types.h>
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#else
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typedef struct arch_spinlock {
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union {
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__ticketpair_t head_tail;
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struct __raw_tickets {
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__ticket_t head, tail;
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} tickets;
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};
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} arch_spinlock_t;
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#define __ARCH_SPIN_LOCK_UNLOCKED { { 0 } }
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#endif /* CONFIG_QUEUED_SPINLOCKS */
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#include <asm-generic/qrwlock_types.h>
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@ -575,9 +575,6 @@ static void kvm_kick_cpu(int cpu)
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kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
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}
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#ifdef CONFIG_QUEUED_SPINLOCKS
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#include <asm/qspinlock.h>
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static void kvm_wait(u8 *ptr, u8 val)
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@ -606,243 +603,6 @@ out:
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local_irq_restore(flags);
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}
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#else /* !CONFIG_QUEUED_SPINLOCKS */
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enum kvm_contention_stat {
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TAKEN_SLOW,
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TAKEN_SLOW_PICKUP,
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RELEASED_SLOW,
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RELEASED_SLOW_KICKED,
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NR_CONTENTION_STATS
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};
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#ifdef CONFIG_KVM_DEBUG_FS
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#define HISTO_BUCKETS 30
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static struct kvm_spinlock_stats
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{
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u32 contention_stats[NR_CONTENTION_STATS];
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u32 histo_spin_blocked[HISTO_BUCKETS+1];
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u64 time_blocked;
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} spinlock_stats;
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static u8 zero_stats;
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static inline void check_zero(void)
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{
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u8 ret;
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u8 old;
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old = READ_ONCE(zero_stats);
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if (unlikely(old)) {
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ret = cmpxchg(&zero_stats, old, 0);
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/* This ensures only one fellow resets the stat */
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if (ret == old)
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memset(&spinlock_stats, 0, sizeof(spinlock_stats));
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}
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}
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static inline void add_stats(enum kvm_contention_stat var, u32 val)
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{
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check_zero();
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spinlock_stats.contention_stats[var] += val;
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}
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static inline u64 spin_time_start(void)
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{
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return sched_clock();
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}
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static void __spin_time_accum(u64 delta, u32 *array)
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{
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unsigned index;
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index = ilog2(delta);
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check_zero();
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if (index < HISTO_BUCKETS)
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array[index]++;
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else
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array[HISTO_BUCKETS]++;
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}
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static inline void spin_time_accum_blocked(u64 start)
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{
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u32 delta;
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delta = sched_clock() - start;
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__spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
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spinlock_stats.time_blocked += delta;
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}
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static struct dentry *d_spin_debug;
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static struct dentry *d_kvm_debug;
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static struct dentry *kvm_init_debugfs(void)
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{
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d_kvm_debug = debugfs_create_dir("kvm-guest", NULL);
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if (!d_kvm_debug)
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printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n");
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return d_kvm_debug;
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}
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static int __init kvm_spinlock_debugfs(void)
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{
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struct dentry *d_kvm;
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d_kvm = kvm_init_debugfs();
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if (d_kvm == NULL)
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return -ENOMEM;
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d_spin_debug = debugfs_create_dir("spinlocks", d_kvm);
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debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
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debugfs_create_u32("taken_slow", 0444, d_spin_debug,
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&spinlock_stats.contention_stats[TAKEN_SLOW]);
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debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
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&spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]);
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debugfs_create_u32("released_slow", 0444, d_spin_debug,
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&spinlock_stats.contention_stats[RELEASED_SLOW]);
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debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
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&spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]);
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debugfs_create_u64("time_blocked", 0444, d_spin_debug,
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&spinlock_stats.time_blocked);
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debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
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spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
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return 0;
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}
|
||||
fs_initcall(kvm_spinlock_debugfs);
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#else /* !CONFIG_KVM_DEBUG_FS */
|
||||
static inline void add_stats(enum kvm_contention_stat var, u32 val)
|
||||
{
|
||||
}
|
||||
|
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static inline u64 spin_time_start(void)
|
||||
{
|
||||
return 0;
|
||||
}
|
||||
|
||||
static inline void spin_time_accum_blocked(u64 start)
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||||
{
|
||||
}
|
||||
#endif /* CONFIG_KVM_DEBUG_FS */
|
||||
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struct kvm_lock_waiting {
|
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struct arch_spinlock *lock;
|
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__ticket_t want;
|
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};
|
||||
|
||||
/* 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)
|
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{
|
||||
struct kvm_lock_waiting *w;
|
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int cpu;
|
||||
u64 start;
|
||||
unsigned long flags;
|
||||
__ticket_t head;
|
||||
|
||||
if (in_nmi())
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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)
|
||||
|
|
|
|||
|
|
@ -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);
|
||||
|
|
|
|||
|
|
@ -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;
|
||||
|
|
|
|||
|
|
@ -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;
|
||||
|
|
|
|||
|
|
@ -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 */
|
||||
|
|
|
|||
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