[PATCH v3 4/5] arm64: locking: Move rwlock implementation over to qrwlocks

From: Will Deacon
Date: Thu Oct 12 2017 - 08:21:23 EST

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Now that the qrwlock can make use of WFE, remove our homebrew rwlock
code in favour of the generic queued implementation.

Tested-by: Waiman Long <longman@xxxxxxxxxx>
Tested-by: Jeremy Linton <jeremy.linton@xxxxxxx>
Tested-by: Adam Wallis <awallis@xxxxxxxxxxxxxx>
Tested-by: Jan Glauber <jglauber@xxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
---
arch/arm64/Kconfig | 17 ++++
arch/arm64/include/asm/Kbuild | 1 +
arch/arm64/include/asm/spinlock.h | 164 +-------------------------------
arch/arm64/include/asm/spinlock_types.h | 6 +-
4 files changed, 20 insertions(+), 168 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0df64a6a56d4..df02ad932020 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -22,7 +22,24 @@ config ARM64
select ARCH_HAS_STRICT_MODULE_RWX
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAVE_NMI_SAFE_CMPXCHG if ACPI_APEI_SEA
+ select ARCH_INLINE_READ_LOCK if !PREEMPT
+ select ARCH_INLINE_READ_LOCK_BH if !PREEMPT
+ select ARCH_INLINE_READ_LOCK_IRQ if !PREEMPT
+ select ARCH_INLINE_READ_LOCK_IRQSAVE if !PREEMPT
+ select ARCH_INLINE_READ_UNLOCK if !PREEMPT
+ select ARCH_INLINE_READ_UNLOCK_BH if !PREEMPT
+ select ARCH_INLINE_READ_UNLOCK_IRQ if !PREEMPT
+ select ARCH_INLINE_READ_UNLOCK_IRQRESTORE if !PREEMPT
+ select ARCH_INLINE_WRITE_LOCK if !PREEMPT
+ select ARCH_INLINE_WRITE_LOCK_BH if !PREEMPT
+ select ARCH_INLINE_WRITE_LOCK_IRQ if !PREEMPT
+ select ARCH_INLINE_WRITE_LOCK_IRQSAVE if !PREEMPT
+ select ARCH_INLINE_WRITE_UNLOCK if !PREEMPT
+ select ARCH_INLINE_WRITE_UNLOCK_BH if !PREEMPT
+ select ARCH_INLINE_WRITE_UNLOCK_IRQ if !PREEMPT
+ select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE if !PREEMPT
select ARCH_USE_CMPXCHG_LOCKREF
+ select ARCH_USE_QUEUED_RWLOCKS
select ARCH_SUPPORTS_MEMORY_FAILURE
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_NUMA_BALANCING
diff --git a/arch/arm64/include/asm/Kbuild b/arch/arm64/include/asm/Kbuild
index 2326e39d5892..e63d0a8312de 100644
--- a/arch/arm64/include/asm/Kbuild
+++ b/arch/arm64/include/asm/Kbuild
@@ -16,6 +16,7 @@ generic-y += mcs_spinlock.h
generic-y += mm-arch-hooks.h
generic-y += msi.h
generic-y += preempt.h
+generic-y += qrwlock.h
generic-y += rwsem.h
generic-y += segment.h
generic-y += serial.h
diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
index aa51a38e46e4..fdb827c7832f 100644
--- a/arch/arm64/include/asm/spinlock.h
+++ b/arch/arm64/include/asm/spinlock.h
@@ -137,169 +137,7 @@ static inline int arch_spin_is_contended(arch_spinlock_t *lock)
}
#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"
- __nops(1),
- /* 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"
- __nops(2))
- : "=&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"
- " cbnz %w1, 2b\n"
- __nops(1),
- /* 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"
- " staddl %w0, %2\n"
- __nops(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"
- __nops(1)
- "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)
+#include <asm/qrwlock.h>

/* See include/linux/spinlock.h */
#define smp_mb__after_spinlock() smp_mb()
diff --git a/arch/arm64/include/asm/spinlock_types.h b/arch/arm64/include/asm/spinlock_types.h
index 55be59a35e3f..6b856012c51b 100644
--- a/arch/arm64/include/asm/spinlock_types.h
+++ b/arch/arm64/include/asm/spinlock_types.h
@@ -36,10 +36,6 @@ typedef struct {

#define __ARCH_SPIN_LOCK_UNLOCKED { 0 , 0 }

-typedef struct {
- volatile unsigned int lock;
-} arch_rwlock_t;
-
-#define __ARCH_RW_LOCK_UNLOCKED { 0 }
+#include <asm-generic/qrwlock_types.h>

#endif
--
2.1.4

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