Merge tag 'generic-ticket-spinlocks-v6' into for-next

asm-generic: New generic ticket-based spinlock

This contains a new ticket-based spinlock that uses only generic
atomics and doesn't require as much from the memory system as qspinlock
does in order to be fair.  It also includes a bit of documentation about
the qspinlock and qrwlock fairness requirements.

This will soon be used by a handful of architectures that don't meet the
qspinlock requirements.

* tag 'generic-ticket-spinlocks-v6':
  csky: Move to generic ticket-spinlock
  RISC-V: Move to queued RW locks
  RISC-V: Move to generic spinlocks
  openrisc: Move to ticket-spinlock
  asm-generic: qrwlock: Document the spinlock fairness requirements
  asm-generic: qspinlock: Indicate the use of mixed-size atomics
  asm-generic: ticket-lock: New generic ticket-based spinlock

11 files changed, 10 insertions, 314 deletions

diff --git a/arch/csky/include/asm/Kbuild b/arch/csky/include/asm/Kbuild
index 888248235c23..103207a58f97 100644
--- a/arch/csky/include/asm/Kbuild
+++ b/arch/csky/include/asm/Kbuild
@@ -3,7 +3,10 @@ generic-y += asm-offsets.h
 generic-y += extable.h
 generic-y += gpio.h
 generic-y += kvm_para.h
+generic-y += spinlock.h
+generic-y += spinlock_types.h
 generic-y += qrwlock.h
+generic-y += qrwlock_types.h
 generic-y += parport.h
 generic-y += user.h
 generic-y += vmlinux.lds.h
diff --git a/arch/csky/include/asm/spinlock.h b/arch/csky/include/asm/spinlock.h
deleted file mode 100644
index 69f5aa249c5f..000000000000
--- a/arch/csky/include/asm/spinlock.h
+++ /dev/null
@@ -1,89 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-
-#ifndef __ASM_CSKY_SPINLOCK_H
-#define __ASM_CSKY_SPINLOCK_H
-
-#include <linux/spinlock_types.h>
-#include <asm/barrier.h>
-
-/*
- * Ticket-based spin-locking.
- */
-static inline void arch_spin_lock(arch_spinlock_t *lock)
-{
-	arch_spinlock_t lockval;
-	u32 ticket_next = 1 << TICKET_NEXT;
-	u32 *p = &lock->lock;
-	u32 tmp;
-
-	asm volatile (
-		"1:	ldex.w		%0, (%2) \n"
-		"	mov		%1, %0	 \n"
-		"	add		%0, %3	 \n"
-		"	stex.w		%0, (%2) \n"
-		"	bez		%0, 1b   \n"
-		: "=&r" (tmp), "=&r" (lockval)
-		: "r"(p), "r"(ticket_next)
-		: "cc");
-
-	while (lockval.tickets.next != lockval.tickets.owner)
-		lockval.tickets.owner = READ_ONCE(lock->tickets.owner);
-
-	smp_mb();
-}
-
-static inline int arch_spin_trylock(arch_spinlock_t *lock)
-{
-	u32 tmp, contended, res;
-	u32 ticket_next = 1 << TICKET_NEXT;
-	u32 *p = &lock->lock;
-
-	do {
-		asm volatile (
-		"	ldex.w		%0, (%3)   \n"
-		"	movi		%2, 1	   \n"
-		"	rotli		%1, %0, 16 \n"
-		"	cmpne		%1, %0     \n"
-		"	bt		1f         \n"
-		"	movi		%2, 0	   \n"
-		"	add		%0, %0, %4 \n"
-		"	stex.w		%0, (%3)   \n"
-		"1:				   \n"
-		: "=&r" (res), "=&r" (tmp), "=&r" (contended)
-		: "r"(p), "r"(ticket_next)
-		: "cc");
-	} while (!res);
-
-	if (!contended)
-		smp_mb();
-
-	return !contended;
-}
-
-static inline void arch_spin_unlock(arch_spinlock_t *lock)
-{
-	smp_mb();
-	WRITE_ONCE(lock->tickets.owner, lock->tickets.owner + 1);
-}
-
-static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
-{
-	return lock.tickets.owner == lock.tickets.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)
-{
-	struct __raw_tickets tickets = READ_ONCE(lock->tickets);
-
-	return (tickets.next - tickets.owner) > 1;
-}
-#define arch_spin_is_contended	arch_spin_is_contended
-
-#include <asm/qrwlock.h>
-
-#endif /* __ASM_CSKY_SPINLOCK_H */
diff --git a/arch/csky/include/asm/spinlock_types.h b/arch/csky/include/asm/spinlock_types.h
deleted file mode 100644
index db87a12c3827..000000000000
--- a/arch/csky/include/asm/spinlock_types.h
+++ /dev/null
@@ -1,27 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-
-#ifndef __ASM_CSKY_SPINLOCK_TYPES_H
-#define __ASM_CSKY_SPINLOCK_TYPES_H
-
-#ifndef __LINUX_SPINLOCK_TYPES_RAW_H
-# error "please don't include this file directly"
-#endif
-
-#define TICKET_NEXT	16
-
-typedef struct {
-	union {
-		u32 lock;
-		struct __raw_tickets {
-			/* little endian */
-			u16 owner;
-			u16 next;
-		} tickets;
-	};
-} arch_spinlock_t;
-
-#define __ARCH_SPIN_LOCK_UNLOCKED	{ { 0 } }
-
-#include <asm-generic/qrwlock_types.h>
-
-#endif /* __ASM_CSKY_SPINLOCK_TYPES_H */
diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index 0d68adf6e02b..99f0e4a4cbbd 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig
@@ -30,7 +30,6 @@ config OPENRISC
 	select HAVE_DEBUG_STACKOVERFLOW
 	select OR1K_PIC
 	select CPU_NO_EFFICIENT_FFS if !OPENRISC_HAVE_INST_FF1
-	select ARCH_USE_QUEUED_SPINLOCKS
 	select ARCH_USE_QUEUED_RWLOCKS
 	select OMPIC if SMP
 	select ARCH_WANT_FRAME_POINTERS
diff --git a/arch/openrisc/include/asm/Kbuild b/arch/openrisc/include/asm/Kbuild
index ca5987e11053..3386b9c1c073 100644
--- a/arch/openrisc/include/asm/Kbuild
+++ b/arch/openrisc/include/asm/Kbuild
@@ -1,9 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 generic-y += extable.h
 generic-y += kvm_para.h
-generic-y += mcs_spinlock.h
-generic-y += qspinlock_types.h
-generic-y += qspinlock.h
+generic-y += spinlock_types.h
+generic-y += spinlock.h
 generic-y += qrwlock_types.h
 generic-y += qrwlock.h
 generic-y += user.h
diff --git a/arch/openrisc/include/asm/spinlock.h b/arch/openrisc/include/asm/spinlock.h
deleted file mode 100644
index 264944a71535..000000000000
--- a/arch/openrisc/include/asm/spinlock.h
+++ /dev/null
@@ -1,27 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
-/*
- * OpenRISC Linux
- *
- * Linux architectural port borrowing liberally from similar works of
- * others.  All original copyrights apply as per the original source
- * declaration.
- *
- * OpenRISC implementation:
- * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
- * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
- * et al.
- */
-
-#ifndef __ASM_OPENRISC_SPINLOCK_H
-#define __ASM_OPENRISC_SPINLOCK_H
-
-#include <asm/qspinlock.h>
-
-#include <asm/qrwlock.h>
-
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
-
-#endif
diff --git a/arch/openrisc/include/asm/spinlock_types.h b/arch/openrisc/include/asm/spinlock_types.h
deleted file mode 100644
index 7c6fb1208c88..000000000000
--- a/arch/openrisc/include/asm/spinlock_types.h
+++ /dev/null
@@ -1,7 +0,0 @@
-#ifndef _ASM_OPENRISC_SPINLOCK_TYPES_H
-#define _ASM_OPENRISC_SPINLOCK_TYPES_H
-
-#include <asm/qspinlock_types.h>
-#include <asm/qrwlock_types.h>
-
-#endif /* _ASM_OPENRISC_SPINLOCK_TYPES_H */
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 0f1dc11b5d7f..f863065b478c 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -39,6 +39,7 @@ config RISCV
 	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
 	select ARCH_SUPPORTS_HUGETLBFS if MMU
 	select ARCH_USE_MEMTEST
+	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_GENERAL_HUGETLB
diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
index 5edf5b8587e7..504f8b7e72d4 100644
--- a/arch/riscv/include/asm/Kbuild
+++ b/arch/riscv/include/asm/Kbuild
@@ -3,5 +3,9 @@ generic-y += early_ioremap.h
 generic-y += flat.h
 generic-y += kvm_para.h
 generic-y += parport.h
+generic-y += spinlock.h
+generic-y += spinlock_types.h
+generic-y += qrwlock.h
+generic-y += qrwlock_types.h
 generic-y += user.h
 generic-y += vmlinux.lds.h
diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h
deleted file mode 100644
index f4f7fa1b7ca8..000000000000
--- a/arch/riscv/include/asm/spinlock.h
+++ /dev/null
@@ -1,135 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * Copyright (C) 2015 Regents of the University of California
- * Copyright (C) 2017 SiFive
- */
-
-#ifndef _ASM_RISCV_SPINLOCK_H
-#define _ASM_RISCV_SPINLOCK_H
-
-#include <linux/kernel.h>
-#include <asm/current.h>
-#include <asm/fence.h>
-
-/*
- * Simple spin lock operations.  These provide no fairness guarantees.
- */
-
-/* FIXME: Replace this with a ticket lock, like MIPS. */
-
-#define arch_spin_is_locked(x)	(READ_ONCE((x)->lock) != 0)
-
-static inline void arch_spin_unlock(arch_spinlock_t *lock)
-{
-	smp_store_release(&lock->lock, 0);
-}
-
-static inline int arch_spin_trylock(arch_spinlock_t *lock)
-{
-	int tmp = 1, busy;
-
-	__asm__ __volatile__ (
-		"	amoswap.w %0, %2, %1\n"
-		RISCV_ACQUIRE_BARRIER
-		: "=r" (busy), "+A" (lock->lock)
-		: "r" (tmp)
-		: "memory");
-
-	return !busy;
-}
-
-static inline void arch_spin_lock(arch_spinlock_t *lock)
-{
-	while (1) {
-		if (arch_spin_is_locked(lock))
-			continue;
-
-		if (arch_spin_trylock(lock))
-			break;
-	}
-}
-
-/***********************************************************/
-
-static inline void arch_read_lock(arch_rwlock_t *lock)
-{
-	int tmp;
-
-	__asm__ __volatile__(
-		"1:	lr.w	%1, %0\n"
-		"	bltz	%1, 1b\n"
-		"	addi	%1, %1, 1\n"
-		"	sc.w	%1, %1, %0\n"
-		"	bnez	%1, 1b\n"
-		RISCV_ACQUIRE_BARRIER
-		: "+A" (lock->lock), "=&r" (tmp)
-		:: "memory");
-}
-
-static inline void arch_write_lock(arch_rwlock_t *lock)
-{
-	int tmp;
-
-	__asm__ __volatile__(
-		"1:	lr.w	%1, %0\n"
-		"	bnez	%1, 1b\n"
-		"	li	%1, -1\n"
-		"	sc.w	%1, %1, %0\n"
-		"	bnez	%1, 1b\n"
-		RISCV_ACQUIRE_BARRIER
-		: "+A" (lock->lock), "=&r" (tmp)
-		:: "memory");
-}
-
-static inline int arch_read_trylock(arch_rwlock_t *lock)
-{
-	int busy;
-
-	__asm__ __volatile__(
-		"1:	lr.w	%1, %0\n"
-		"	bltz	%1, 1f\n"
-		"	addi	%1, %1, 1\n"
-		"	sc.w	%1, %1, %0\n"
-		"	bnez	%1, 1b\n"
-		RISCV_ACQUIRE_BARRIER
-		"1:\n"
-		: "+A" (lock->lock), "=&r" (busy)
-		:: "memory");
-
-	return !busy;
-}
-
-static inline int arch_write_trylock(arch_rwlock_t *lock)
-{
-	int busy;
-
-	__asm__ __volatile__(
-		"1:	lr.w	%1, %0\n"
-		"	bnez	%1, 1f\n"
-		"	li	%1, -1\n"
-		"	sc.w	%1, %1, %0\n"
-		"	bnez	%1, 1b\n"
-		RISCV_ACQUIRE_BARRIER
-		"1:\n"
-		: "+A" (lock->lock), "=&r" (busy)
-		:: "memory");
-
-	return !busy;
-}
-
-static inline void arch_read_unlock(arch_rwlock_t *lock)
-{
-	__asm__ __volatile__(
-		RISCV_RELEASE_BARRIER
-		"	amoadd.w x0, %1, %0\n"
-		: "+A" (lock->lock)
-		: "r" (-1)
-		: "memory");
-}
-
-static inline void arch_write_unlock(arch_rwlock_t *lock)
-{
-	smp_store_release(&lock->lock, 0);
-}
-
-#endif /* _ASM_RISCV_SPINLOCK_H */
diff --git a/arch/riscv/include/asm/spinlock_types.h b/arch/riscv/include/asm/spinlock_types.h
deleted file mode 100644
index 5a35a49505da..000000000000
--- a/arch/riscv/include/asm/spinlock_types.h
+++ /dev/null
@@ -1,25 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * Copyright (C) 2015 Regents of the University of California
- */
-
-#ifndef _ASM_RISCV_SPINLOCK_TYPES_H
-#define _ASM_RISCV_SPINLOCK_TYPES_H
-
-#ifndef __LINUX_SPINLOCK_TYPES_RAW_H
-# error "please don't include this file directly"
-#endif
-
-typedef struct {
-	volatile unsigned int lock;
-} arch_spinlock_t;
-
-#define __ARCH_SPIN_LOCK_UNLOCKED	{ 0 }
-
-typedef struct {
-	volatile unsigned int lock;
-} arch_rwlock_t;
-
-#define __ARCH_RW_LOCK_UNLOCKED		{ 0 }
-
-#endif /* _ASM_RISCV_SPINLOCK_TYPES_H */