From: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Our existing spinlocks aren't fair and replacing them has been on the
TODO list for a long time. This moves to the recently-introduced ticket
spinlocks, which are simple enough that they are likely to be correct
and fast on the vast majority of extant implementations.
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
---
arch/riscv/include/asm/Kbuild | 2 ++
arch/riscv/include/asm/spinlock.h | 41 +------------------------
arch/riscv/include/asm/spinlock_types.h | 6 +---
3 files changed, 4 insertions(+), 45 deletions(-)
diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
index 57b86fd9916c..42b1961af1a6 100644
--- a/arch/riscv/include/asm/Kbuild
+++ b/arch/riscv/include/asm/Kbuild
@@ -2,5 +2,7 @@
generic-y += early_ioremap.h
generic-y += flat.h
generic-y += kvm_para.h
+generic-y += ticket-lock.h
+generic-y += ticket-lock-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
index f4f7fa1b7ca8..38089cbdea92 100644
--- a/arch/riscv/include/asm/spinlock.h
+++ b/arch/riscv/include/asm/spinlock.h
@@ -10,46 +10,7 @@
#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;
- }
-}
-
-/***********************************************************/
+#include <asm-generic/ticket-lock.h>
static inline void arch_read_lock(arch_rwlock_t *lock)
{
diff --git a/arch/riscv/include/asm/spinlock_types.h b/arch/riscv/include/asm/spinlock_types.h
index 5a35a49505da..431ee08e26c4 100644
--- a/arch/riscv/include/asm/spinlock_types.h
+++ b/arch/riscv/include/asm/spinlock_types.h
@@ -10,11 +10,7 @@
# error "please don't include this file directly"
#endif
-typedef struct {
- volatile unsigned int lock;
-} arch_spinlock_t;
-
-#define __ARCH_SPIN_LOCK_UNLOCKED { 0 }
+#include <asm-generic/ticket-lock-types.h>
typedef struct {
volatile unsigned int lock;
--
2.34.1
