RISC-V: Move to generic spinlocks

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.

This introduces a horrible hack that allows us to split out the spinlock
conversion from the rwlock conversion.  We have to do the spinlocks
first because qrwlock needs fair spinlocks, but we don't want to pollute
the asm-generic code to support the generic spinlocks without qrwlocks.
Thus we pollute the RISC-V code, but just until the next commit as it's
all going away.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Guo Ren <guoren@kernel.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
index 5edf5b8587e7d987e38676cde811c735e6e65877..c3f229ae80330f2d6faf196dd17b99192264ba0c 100644 (file)
--- a/arch/riscv/include/asm/Kbuild
+++ b/arch/riscv/include/asm/Kbuild
@@ -3,5 +3,7 @@ generic-y += early_ioremap.h
 generic-y += flat.h
 generic-y += kvm_para.h
 generic-y += parport.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
index f4f7fa1b7ca87606aa0c741c2617c1b72aded256..88a4d5d0d98ab2e7f83d195960b4854fe0baa9c9 100644 (file)
--- a/arch/riscv/include/asm/spinlock.h
+++ b/arch/riscv/include/asm/spinlock.h
@@ -7,49 +7,13 @@
 #ifndef _ASM_RISCV_SPINLOCK_H
 #define _ASM_RISCV_SPINLOCK_H
 
+/* This is horible, but the whole file is going away in the next commit. */
+#define __ASM_GENERIC_QRWLOCK_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;
-       }
-}
-
-/***********************************************************/
+#include <asm-generic/spinlock.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 5a35a49505da26105596f5d800530312d8c6d217..f2f9b5d7120d1d4f6f972b993b71ebb73ac57b36 100644 (file)
--- a/arch/riscv/include/asm/spinlock_types.h
+++ b/arch/riscv/include/asm/spinlock_types.h
@@ -6,15 +6,14 @@
 #ifndef _ASM_RISCV_SPINLOCK_TYPES_H
 #define _ASM_RISCV_SPINLOCK_TYPES_H
 
+/* This is horible, but the whole file is going away in the next commit. */
+#define __ASM_GENERIC_QRWLOCK_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 }
+#include <asm-generic/spinlock_types.h>
 
 typedef struct {
        volatile unsigned int lock;