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b3a73b7db2
This uses more optimal ll/sc style access patterns (rather than cmpxchg), and also sets the EH=1 lock hint on those operations which acquire ownership of the lock. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20221126095932.1234527-4-npiggin@gmail.com
71 lines
1.7 KiB
C
71 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_POWERPC_QSPINLOCK_H
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#define _ASM_POWERPC_QSPINLOCK_H
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#include <linux/compiler.h>
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#include <asm/qspinlock_types.h>
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#include <asm/paravirt.h>
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static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
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{
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return READ_ONCE(lock->val);
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}
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static __always_inline int queued_spin_value_unlocked(struct qspinlock lock)
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{
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return !lock.val;
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}
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static __always_inline int queued_spin_is_contended(struct qspinlock *lock)
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{
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return !!(READ_ONCE(lock->val) & _Q_TAIL_CPU_MASK);
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}
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static __always_inline int queued_spin_trylock(struct qspinlock *lock)
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{
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u32 prev;
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asm volatile(
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"1: lwarx %0,0,%1,%3 # queued_spin_trylock \n"
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" cmpwi 0,%0,0 \n"
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" bne- 2f \n"
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" stwcx. %2,0,%1 \n"
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" bne- 1b \n"
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"\t" PPC_ACQUIRE_BARRIER " \n"
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"2: \n"
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: "=&r" (prev)
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: "r" (&lock->val), "r" (_Q_LOCKED_VAL),
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"i" (IS_ENABLED(CONFIG_PPC64))
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: "cr0", "memory");
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return likely(prev == 0);
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}
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void queued_spin_lock_slowpath(struct qspinlock *lock);
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static __always_inline void queued_spin_lock(struct qspinlock *lock)
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{
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if (!queued_spin_trylock(lock))
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queued_spin_lock_slowpath(lock);
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}
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static inline void queued_spin_unlock(struct qspinlock *lock)
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{
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smp_store_release(&lock->locked, 0);
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}
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#define arch_spin_is_locked(l) queued_spin_is_locked(l)
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#define arch_spin_is_contended(l) queued_spin_is_contended(l)
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#define arch_spin_value_unlocked(l) queued_spin_value_unlocked(l)
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#define arch_spin_lock(l) queued_spin_lock(l)
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#define arch_spin_trylock(l) queued_spin_trylock(l)
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#define arch_spin_unlock(l) queued_spin_unlock(l)
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#ifdef CONFIG_PARAVIRT_SPINLOCKS
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void pv_spinlocks_init(void);
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#else
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static inline void pv_spinlocks_init(void) { }
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#endif
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#endif /* _ASM_POWERPC_QSPINLOCK_H */
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