[PATCH 2/5] riscv: Add QUEUED_SPINLOCKS & QUEUED_RWLOCKS supported

guoren
2020-11-24T13:52:05Z

From: Guo Ren <guoren@linux.alibaba.com>

riscv only support lr.wd/s(c).w(d) with word(double word) size &
align access. There are not lr.h/sc.h instructions. But qspinlock.c
need xchg with short type variable:

xchg_tail -> xchg_releaxed(&lock->tail, ...

typedef struct qspinlock {
union {
atomic_t val;

/*
* By using the whole 2nd least significant byte for the
* pending bit, we can allow better optimization of the lock
* acquisition for the pending bit holder.
*/
struct {
u8 locked;
u8 pending;
};
struct {
u16 locked_pending;
u16 tail; /* half word*/
};
};
} arch_spinlock_t;

So we add short emulation in xchg with word length and it only
solve qspinlock's requirement.

Michael have sent qspinlock before, ref to Link below.

Link: https://lore.kernel.org/linux-riscv/20190211043829.30096-1-michaeljclark@mac.com/
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michael Clark <michaeljclark@mac.com>
---
arch/riscv/Kconfig | 2 +
arch/riscv/include/asm/Kbuild | 3 +
arch/riscv/include/asm/cmpxchg.h | 36 +++++++++
arch/riscv/include/asm/spinlock.h | 126 +-------------------------------
arch/riscv/include/asm/spinlock_types.h | 15 +---
5 files changed, 46 insertions(+), 136 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 2d61c4c..d757ba4 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -36,6 +36,8 @@ config RISCV
select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
select ARCH_WANT_FRAME_POINTERS
select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
+ select ARCH_USE_QUEUED_RWLOCKS
+ select ARCH_USE_QUEUED_SPINLOCKS
select CLONE_BACKWARDS
select CLINT_TIMER if !MMU
select COMMON_CLK
diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
index 59dd7be..6f5f438 100644
--- a/arch/riscv/include/asm/Kbuild
+++ b/arch/riscv/include/asm/Kbuild
@@ -6,3 +6,6 @@ generic-y += kvm_para.h
generic-y += local64.h
generic-y += user.h
generic-y += vmlinux.lds.h
+generic-y += mcs_spinlock.h
+generic-y += qrwlock.h
+generic-y += qspinlock.h
diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
index 5609185..e178700 100644
--- a/arch/riscv/include/asm/cmpxchg.h
+++ b/arch/riscv/include/asm/cmpxchg.h
@@ -16,7 +16,43 @@
__typeof__(ptr) __ptr = (ptr); \
__typeof__(new) __new = (new); \
__typeof__(*(ptr)) __ret; \
+ register unsigned long __rc, tmp, align, addr; \
switch (size) { \
+ case 2: \
+ align = ((unsigned long) __ptr & 0x3); \
+ addr = ((unsigned long) __ptr & ~0x3); \
+ if (align) { \
+ __asm__ __volatile__ ( \
+ "0: lr.w %0, 0(%z4)\n" \
+ " move %1, %0\n" \
+ " slli %1, %1, 16\n" \
+ " srli %1, %1, 16\n" \
+ " move %2, %z3\n" \
+ " slli %2, %2, 16\n" \
+ " or %1, %2, %1\n" \
+ " sc.w %2, %1, 0(%z4)\n" \
+ " bnez %2, 0b\n" \
+ " srli %0, %0, 16\n" \
+ : "=&r" (__ret), "=&r" (tmp), "=&r" (__rc) \
+ : "rJ" (__new), "rJ"(addr) \
+ : "memory"); \
+ } else { \
+ __asm__ __volatile__ ( \
+ "0: lr.w %0, (%z4)\n" \
+ " move %1, %0\n" \
+ " srli %1, %1, 16\n" \
+ " slli %1, %1, 16\n" \
+ " move %2, %z3\n" \
+ " or %1, %2, %1\n" \
+ " sc.w %2, %1, 0(%z4)\n" \
+ " bnez %2, 0b\n" \
+ " slli %0, %0, 16\n" \
+ " srli %0, %0, 16\n" \
+ : "=&r" (__ret), "=&r" (tmp), "=&r" (__rc) \
+ : "rJ" (__new), "rJ"(addr) \
+ : "memory"); \
+ } \
+ break; \
case 4: \
__asm__ __volatile__ ( \
" amoswap.w %0, %2, %1\n" \
diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h
index f4f7fa1..b8deb3a 100644
--- a/arch/riscv/include/asm/spinlock.h
+++ b/arch/riscv/include/asm/spinlock.h
@@ -7,129 +7,7 @@
#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);
-}
+#include <asm/qrwlock.h>
+#include <asm/qspinlock.h>

#endif /* _ASM_RISCV_SPINLOCK_H */
diff --git a/arch/riscv/include/asm/spinlock_types.h b/arch/riscv/include/asm/spinlock_types.h
index f398e76..d033a97 100644
--- a/arch/riscv/include/asm/spinlock_types.h
+++ b/arch/riscv/include/asm/spinlock_types.h
@@ -6,20 +6,11 @@
#ifndef _ASM_RISCV_SPINLOCK_TYPES_H
#define _ASM_RISCV_SPINLOCK_TYPES_H

-#ifndef __LINUX_SPINLOCK_TYPES_H
+#if !defined(__LINUX_SPINLOCK_TYPES_H) && !defined(_ASM_RISCV_SPINLOCK_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 }
+#include <asm-generic/qspinlock_types.h>
+#include <asm-generic/qrwlock_types.h>

#endif /* _ASM_RISCV_SPINLOCK_TYPES_H */
--
2.7.4