arch/arm64/include/asm/spinlock.h - kernel/bruno - Git at Google

 /*
  * Copyright (C) 2012 ARM Ltd.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 #ifndef __ASM_SPINLOCK_H
 #define __ASM_SPINLOCK_H

 #include <asm/lse.h>
 #include <asm/spinlock_types.h>
 #include <asm/processor.h>

 /*
  * Spinlock implementation.
  *
  * The memory barriers are implicit with the load-acquire and store-release
  * instructions.
  */

 #define arch_spin_unlock_wait(lock) \
 	do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)

 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)

 static inline void arch_spin_lock(arch_spinlock_t *lock)
 {
 	unsigned int tmp;
 	arch_spinlock_t lockval, newval;

 	asm volatile(
 	/* Atomically increment the next ticket. */
 	ARM64_LSE_ATOMIC_INSN(
 	/* LL/SC */
 "	prfm	pstl1strm, %3\n"
 "1:	ldaxr	%w0, %3\n"
 "	add	%w1, %w0, %w5\n"
 "	stxr	%w2, %w1, %3\n"
 "	cbnz	%w2, 1b\n",
 	/* LSE atomics */
 "	mov	%w2, %w5\n"
 "	ldadda	%w2, %w0, %3\n"
 "	nop\n"
 "	nop\n"
 "	nop\n"
 	)

 	/* Did we get the lock? */
 "	eor	%w1, %w0, %w0, ror #16\n"
 "	cbz	%w1, 3f\n"
 	/*
 	 * No: spin on the owner. Send a local event to avoid missing an
 	 * unlock before the exclusive load.
 	 */
 "	sevl\n"
 "2:	wfe\n"
 "	ldaxrh	%w2, %4\n"
 "	eor	%w1, %w2, %w0, lsr #16\n"
 "	cbnz	%w1, 2b\n"
 	/* We got the lock. Critical section starts here. */
 "3:"
 	: "=&r" (lockval), "=&r" (newval), "=&r" (tmp), "+Q" (*lock)
 	: "Q" (lock->owner), "I" (1 << TICKET_SHIFT)
 	: "memory");
 }

 static inline int arch_spin_trylock(arch_spinlock_t *lock)
 {
 	unsigned int tmp;
 	arch_spinlock_t lockval;

 	asm volatile(ARM64_LSE_ATOMIC_INSN(
 	/* LL/SC */
 	"	prfm	pstl1strm, %2\n"
 	"1:	ldaxr	%w0, %2\n"
 	"	eor	%w1, %w0, %w0, ror #16\n"
 	"	cbnz	%w1, 2f\n"
 	"	add	%w0, %w0, %3\n"
 	"	stxr	%w1, %w0, %2\n"
 	"	cbnz	%w1, 1b\n"
 	"2:",
 	/* LSE atomics */
 	"	ldr	%w0, %2\n"
 	"	eor	%w1, %w0, %w0, ror #16\n"
 	"	cbnz	%w1, 1f\n"
 	"	add	%w1, %w0, %3\n"
 	"	casa	%w0, %w1, %2\n"
 	"	and	%w1, %w1, #0xffff\n"
 	"	eor	%w1, %w1, %w0, lsr #16\n"
 	"1:")
 	: "=&r" (lockval), "=&r" (tmp), "+Q" (*lock)
 	: "I" (1 << TICKET_SHIFT)
 	: "memory");

 	return !tmp;
 }

 static inline void arch_spin_unlock(arch_spinlock_t *lock)
 {
 	unsigned long tmp;

 	asm volatile(ARM64_LSE_ATOMIC_INSN(
 	/* LL/SC */
 	"	ldrh	%w1, %0\n"
 	"	add	%w1, %w1, #1\n"
 	"	stlrh	%w1, %0",
 	/* LSE atomics */
 	"	mov	%w1, #1\n"
 	"	nop\n"
 	"	staddlh	%w1, %0")
 	: "=Q" (lock->owner), "=&r" (tmp)
 	:
 	: "memory");
 }

 static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
 {
 	return lock.owner == lock.next;
 }

 static inline int arch_spin_is_locked(arch_spinlock_t *lock)
 {
 	return !arch_spin_value_unlocked(READ_ONCE(*lock));
 }

 static inline int arch_spin_is_contended(arch_spinlock_t *lock)
 {
 	arch_spinlock_t lockval = READ_ONCE(*lock);
 	return (lockval.next - lockval.owner) > 1;
 }
 #define arch_spin_is_contended	arch_spin_is_contended

 /*
  * Write lock implementation.
  *
  * Write locks set bit 31. Unlocking, is done by writing 0 since the lock is
  * exclusively held.
  *
  * The memory barriers are implicit with the load-acquire and store-release
  * instructions.
  */

 static inline void arch_write_lock(arch_rwlock_t *rw)
 {
 	unsigned int tmp;

 	asm volatile(ARM64_LSE_ATOMIC_INSN(
 	/* LL/SC */
 	"	sevl\n"
 	"1:	wfe\n"
 	"2:	ldaxr	%w0, %1\n"
 	"	cbnz	%w0, 1b\n"
 	"	stxr	%w0, %w2, %1\n"
 	"	cbnz	%w0, 2b\n"
 	"	nop",
 	/* LSE atomics */
 	"1:	mov	%w0, wzr\n"
 	"2:	casa	%w0, %w2, %1\n"
 	"	cbz	%w0, 3f\n"
 	"	ldxr	%w0, %1\n"
 	"	cbz	%w0, 2b\n"
 	"	wfe\n"
 	"	b	1b\n"
 	"3:")
 	: "=&r" (tmp), "+Q" (rw->lock)
 	: "r" (0x80000000)
 	: "memory");
 }

 static inline int arch_write_trylock(arch_rwlock_t *rw)
 {
 	unsigned int tmp;

 	asm volatile(ARM64_LSE_ATOMIC_INSN(
 	/* LL/SC */
 	"1:	ldaxr	%w0, %1\n"
 	"	cbnz	%w0, 2f\n"
 	"	stxr	%w0, %w2, %1\n"
 	"	cbnz	%w0, 1b\n"
 	"2:",
 	/* LSE atomics */
 	"	mov	%w0, wzr\n"
 	"	casa	%w0, %w2, %1\n"
 	"	nop\n"
 	"	nop")
 	: "=&r" (tmp), "+Q" (rw->lock)
 	: "r" (0x80000000)
 	: "memory");

 	return !tmp;
 }

 static inline void arch_write_unlock(arch_rwlock_t *rw)
 {
 	asm volatile(ARM64_LSE_ATOMIC_INSN(
 	"	stlr	wzr, %0",
 	"	swpl	wzr, wzr, %0")
 	: "=Q" (rw->lock) :: "memory");
 }

 /* write_can_lock - would write_trylock() succeed? */
 #define arch_write_can_lock(x)		((x)->lock == 0)

 /*
  * Read lock implementation.
  *
  * It exclusively loads the lock value, increments it and stores the new value
  * back if positive and the CPU still exclusively owns the location. If the
  * value is negative, the lock is already held.
  *
  * During unlocking there may be multiple active read locks but no write lock.
  *
  * The memory barriers are implicit with the load-acquire and store-release
  * instructions.
  *
  * Note that in UNDEFINED cases, such as unlocking a lock twice, the LL/SC
  * and LSE implementations may exhibit different behaviour (although this
  * will have no effect on lockdep).
  */
 static inline void arch_read_lock(arch_rwlock_t *rw)
 {
 	unsigned int tmp, tmp2;

 	asm volatile(
 	"	sevl\n"
 	ARM64_LSE_ATOMIC_INSN(
 	/* LL/SC */
 	"1:	wfe\n"
 	"2:	ldaxr	%w0, %2\n"
 	"	add	%w0, %w0, #1\n"
 	"	tbnz	%w0, #31, 1b\n"
 	"	stxr	%w1, %w0, %2\n"
 	"	nop\n"
 	"	cbnz	%w1, 2b",
 	/* LSE atomics */
 	"1:	wfe\n"
 	"2:	ldxr	%w0, %2\n"
 	"	adds	%w1, %w0, #1\n"
 	"	tbnz	%w1, #31, 1b\n"
 	"	casa	%w0, %w1, %2\n"
 	"	sbc	%w0, %w1, %w0\n"
 	"	cbnz	%w0, 2b")
 	: "=&r" (tmp), "=&r" (tmp2), "+Q" (rw->lock)
 	:
 	: "cc", "memory");
 }

 static inline void arch_read_unlock(arch_rwlock_t *rw)
 {
 	unsigned int tmp, tmp2;

 	asm volatile(ARM64_LSE_ATOMIC_INSN(
 	/* LL/SC */
 	"1:	ldxr	%w0, %2\n"
 	"	sub	%w0, %w0, #1\n"
 	"	stlxr	%w1, %w0, %2\n"
 	"	cbnz	%w1, 1b",
 	/* LSE atomics */
 	"	movn	%w0, #0\n"
 	"	nop\n"
 	"	nop\n"
 	"	staddl	%w0, %2")
 	: "=&r" (tmp), "=&r" (tmp2), "+Q" (rw->lock)
 	:
 	: "memory");
 }

 static inline int arch_read_trylock(arch_rwlock_t *rw)
 {
 	unsigned int tmp, tmp2;

 	asm volatile(ARM64_LSE_ATOMIC_INSN(
 	/* LL/SC */
 	"	mov	%w1, #1\n"
 	"1:	ldaxr	%w0, %2\n"
 	"	add	%w0, %w0, #1\n"
 	"	tbnz	%w0, #31, 2f\n"
 	"	stxr	%w1, %w0, %2\n"
 	"	cbnz	%w1, 1b\n"
 	"2:",
 	/* LSE atomics */
 	"	ldr	%w0, %2\n"
 	"	adds	%w1, %w0, #1\n"
 	"	tbnz	%w1, #31, 1f\n"
 	"	casa	%w0, %w1, %2\n"
 	"	sbc	%w1, %w1, %w0\n"
 	"	nop\n"
 	"1:")
 	: "=&r" (tmp), "=&r" (tmp2), "+Q" (rw->lock)
 	:
 	: "cc", "memory");

 	return !tmp2;
 }

 /* read_can_lock - would read_trylock() succeed? */
 #define arch_read_can_lock(x)		((x)->lock < 0x80000000)

 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)

 #define arch_spin_relax(lock)	cpu_relax()
 #define arch_read_relax(lock)	cpu_relax()
 #define arch_write_relax(lock)	cpu_relax()

 /*
  * Accesses appearing in program order before a spin_lock() operation
  * can be reordered with accesses inside the critical section, by virtue
  * of arch_spin_lock being constructed using acquire semantics.
  *
  * In cases where this is problematic (e.g. try_to_wake_up), an
  * smp_mb__before_spinlock() can restore the required ordering.
  */
 #define smp_mb__before_spinlock()	smp_mb()

 #endif /* __ASM_SPINLOCK_H */
	/*
	* Copyright (C) 2012 ARM Ltd.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	*/
	#ifndef __ASM_SPINLOCK_H
	#define __ASM_SPINLOCK_H

	#include <asm/lse.h>
	#include <asm/spinlock_types.h>
	#include <asm/processor.h>

	/*
	* Spinlock implementation.
	*
	* The memory barriers are implicit with the load-acquire and store-release
	* instructions.
	*/

	#define arch_spin_unlock_wait(lock) \
	do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)

	#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)

	static inline void arch_spin_lock(arch_spinlock_t *lock)
	{
	unsigned int tmp;
	arch_spinlock_t lockval, newval;

	asm volatile(
	/* Atomically increment the next ticket. */
	ARM64_LSE_ATOMIC_INSN(
	/* LL/SC */
	" prfm pstl1strm, %3\n"
	"1: ldaxr %w0, %3\n"
	" add %w1, %w0, %w5\n"
	" stxr %w2, %w1, %3\n"
	" cbnz %w2, 1b\n",
	/* LSE atomics */
	" mov %w2, %w5\n"
	" ldadda %w2, %w0, %3\n"
	" nop\n"
	" nop\n"
	" nop\n"
	)

	/* Did we get the lock? */
	" eor %w1, %w0, %w0, ror #16\n"
	" cbz %w1, 3f\n"
	/*
	* No: spin on the owner. Send a local event to avoid missing an
	* unlock before the exclusive load.
	*/
	" sevl\n"
	"2: wfe\n"
	" ldaxrh %w2, %4\n"
	" eor %w1, %w2, %w0, lsr #16\n"
	" cbnz %w1, 2b\n"
	/* We got the lock. Critical section starts here. */
	"3:"
	: "=&r" (lockval), "=&r" (newval), "=&r" (tmp), "+Q" (*lock)
	: "Q" (lock->owner), "I" (1 << TICKET_SHIFT)
	: "memory");
	}

	static inline int arch_spin_trylock(arch_spinlock_t *lock)
	{
	unsigned int tmp;
	arch_spinlock_t lockval;

	asm volatile(ARM64_LSE_ATOMIC_INSN(
	/* LL/SC */
	" prfm pstl1strm, %2\n"
	"1: ldaxr %w0, %2\n"
	" eor %w1, %w0, %w0, ror #16\n"
	" cbnz %w1, 2f\n"
	" add %w0, %w0, %3\n"
	" stxr %w1, %w0, %2\n"
	" cbnz %w1, 1b\n"
	"2:",
	/* LSE atomics */
	" ldr %w0, %2\n"
	" eor %w1, %w0, %w0, ror #16\n"
	" cbnz %w1, 1f\n"
	" add %w1, %w0, %3\n"
	" casa %w0, %w1, %2\n"
	" and %w1, %w1, #0xffff\n"
	" eor %w1, %w1, %w0, lsr #16\n"
	"1:")
	: "=&r" (lockval), "=&r" (tmp), "+Q" (*lock)
	: "I" (1 << TICKET_SHIFT)
	: "memory");

	return !tmp;
	}

	static inline void arch_spin_unlock(arch_spinlock_t *lock)
	{
	unsigned long tmp;

	asm volatile(ARM64_LSE_ATOMIC_INSN(
	/* LL/SC */
	" ldrh %w1, %0\n"
	" add %w1, %w1, #1\n"
	" stlrh %w1, %0",
	/* LSE atomics */
	" mov %w1, #1\n"
	" nop\n"
	" staddlh %w1, %0")
	: "=Q" (lock->owner), "=&r" (tmp)
	:
	: "memory");
	}

	static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
	{
	return lock.owner == lock.next;
	}

	static inline int arch_spin_is_locked(arch_spinlock_t *lock)
	{
	return !arch_spin_value_unlocked(READ_ONCE(*lock));
	}

	static inline int arch_spin_is_contended(arch_spinlock_t *lock)
	{
	arch_spinlock_t lockval = READ_ONCE(*lock);
	return (lockval.next - lockval.owner) > 1;
	}
	#define arch_spin_is_contended arch_spin_is_contended

	/*
	* Write lock implementation.
	*
	* Write locks set bit 31. Unlocking, is done by writing 0 since the lock is
	* exclusively held.
	*
	* The memory barriers are implicit with the load-acquire and store-release
	* instructions.
	*/

	static inline void arch_write_lock(arch_rwlock_t *rw)
	{
	unsigned int tmp;

	asm volatile(ARM64_LSE_ATOMIC_INSN(
	/* LL/SC */
	" sevl\n"
	"1: wfe\n"
	"2: ldaxr %w0, %1\n"
	" cbnz %w0, 1b\n"
	" stxr %w0, %w2, %1\n"
	" cbnz %w0, 2b\n"
	" nop",
	/* LSE atomics */
	"1: mov %w0, wzr\n"
	"2: casa %w0, %w2, %1\n"
	" cbz %w0, 3f\n"
	" ldxr %w0, %1\n"
	" cbz %w0, 2b\n"
	" wfe\n"
	" b 1b\n"
	"3:")
	: "=&r" (tmp), "+Q" (rw->lock)
	: "r" (0x80000000)
	: "memory");
	}

	static inline int arch_write_trylock(arch_rwlock_t *rw)
	{
	unsigned int tmp;

	asm volatile(ARM64_LSE_ATOMIC_INSN(
	/* LL/SC */
	"1: ldaxr %w0, %1\n"
	" cbnz %w0, 2f\n"
	" stxr %w0, %w2, %1\n"
	" cbnz %w0, 1b\n"
	"2:",
	/* LSE atomics */
	" mov %w0, wzr\n"
	" casa %w0, %w2, %1\n"
	" nop\n"
	" nop")
	: "=&r" (tmp), "+Q" (rw->lock)
	: "r" (0x80000000)
	: "memory");

	return !tmp;
	}

	static inline void arch_write_unlock(arch_rwlock_t *rw)
	{
	asm volatile(ARM64_LSE_ATOMIC_INSN(
	" stlr wzr, %0",
	" swpl wzr, wzr, %0")
	: "=Q" (rw->lock) :: "memory");
	}

	/* write_can_lock - would write_trylock() succeed? */
	#define arch_write_can_lock(x) ((x)->lock == 0)

	/*
	* Read lock implementation.
	*
	* It exclusively loads the lock value, increments it and stores the new value
	* back if positive and the CPU still exclusively owns the location. If the
	* value is negative, the lock is already held.
	*
	* During unlocking there may be multiple active read locks but no write lock.
	*
	* The memory barriers are implicit with the load-acquire and store-release
	* instructions.
	*
	* Note that in UNDEFINED cases, such as unlocking a lock twice, the LL/SC
	* and LSE implementations may exhibit different behaviour (although this
	* will have no effect on lockdep).
	*/
	static inline void arch_read_lock(arch_rwlock_t *rw)
	{
	unsigned int tmp, tmp2;

	asm volatile(
	" sevl\n"
	ARM64_LSE_ATOMIC_INSN(
	/* LL/SC */
	"1: wfe\n"
	"2: ldaxr %w0, %2\n"
	" add %w0, %w0, #1\n"
	" tbnz %w0, #31, 1b\n"
	" stxr %w1, %w0, %2\n"
	" nop\n"
	" cbnz %w1, 2b",
	/* LSE atomics */
	"1: wfe\n"
	"2: ldxr %w0, %2\n"
	" adds %w1, %w0, #1\n"
	" tbnz %w1, #31, 1b\n"
	" casa %w0, %w1, %2\n"
	" sbc %w0, %w1, %w0\n"
	" cbnz %w0, 2b")
	: "=&r" (tmp), "=&r" (tmp2), "+Q" (rw->lock)
	:
	: "cc", "memory");
	}

	static inline void arch_read_unlock(arch_rwlock_t *rw)
	{
	unsigned int tmp, tmp2;

	asm volatile(ARM64_LSE_ATOMIC_INSN(
	/* LL/SC */
	"1: ldxr %w0, %2\n"
	" sub %w0, %w0, #1\n"
	" stlxr %w1, %w0, %2\n"
	" cbnz %w1, 1b",
	/* LSE atomics */
	" movn %w0, #0\n"
	" nop\n"
	" nop\n"
	" staddl %w0, %2")
	: "=&r" (tmp), "=&r" (tmp2), "+Q" (rw->lock)
	:
	: "memory");
	}

	static inline int arch_read_trylock(arch_rwlock_t *rw)
	{
	unsigned int tmp, tmp2;

	asm volatile(ARM64_LSE_ATOMIC_INSN(
	/* LL/SC */
	" mov %w1, #1\n"
	"1: ldaxr %w0, %2\n"
	" add %w0, %w0, #1\n"
	" tbnz %w0, #31, 2f\n"
	" stxr %w1, %w0, %2\n"
	" cbnz %w1, 1b\n"
	"2:",
	/* LSE atomics */
	" ldr %w0, %2\n"
	" adds %w1, %w0, #1\n"
	" tbnz %w1, #31, 1f\n"
	" casa %w0, %w1, %2\n"
	" sbc %w1, %w1, %w0\n"
	" nop\n"
	"1:")
	: "=&r" (tmp), "=&r" (tmp2), "+Q" (rw->lock)
	:
	: "cc", "memory");

	return !tmp2;
	}

	/* read_can_lock - would read_trylock() succeed? */
	#define arch_read_can_lock(x) ((x)->lock < 0x80000000)

	#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
	#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)

	#define arch_spin_relax(lock) cpu_relax()
	#define arch_read_relax(lock) cpu_relax()
	#define arch_write_relax(lock) cpu_relax()

	/*
	* Accesses appearing in program order before a spin_lock() operation
	* can be reordered with accesses inside the critical section, by virtue
	* of arch_spin_lock being constructed using acquire semantics.
	*
	* In cases where this is problematic (e.g. try_to_wake_up), an
	* smp_mb__before_spinlock() can restore the required ordering.
	*/
	#define smp_mb__before_spinlock() smp_mb()

	#endif /* __ASM_SPINLOCK_H */