sparc64: Make rwsems 64-bit.
David S. Miller [Wed, 18 Aug 2010 05:49:26 +0000 (22:49 -0700)]
Basically tip-off the powerpc code, use a 64-bit type and atomic64_t
interfaces for the implementation.

This gets us off of the by-hand asm code I wrote, which frankly I
think probably ruins I-cache hit rates.

The idea was the keep the call chains less deep, but anything taking
the rw-semaphores probably is also calling other stuff and therefore
already has allocated a stack-frame.  So no real stack frame savings
ever.

Ben H. has posted patches to make powerpc use 64-bit too and with some
abstractions we can probably use a shared header file somewhere.

With suggestions from Sam Ravnborg.

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/include/asm/rwsem-const.h [deleted file]
arch/sparc/include/asm/rwsem.h
arch/sparc/lib/Makefile
arch/sparc/lib/rwsem_64.S [deleted file]

diff --git a/arch/sparc/include/asm/rwsem-const.h b/arch/sparc/include/asm/rwsem-const.h
deleted file mode 100644 (file)
index e4c61a1..0000000
+++ /dev/null
@@ -1,12 +0,0 @@
-/* rwsem-const.h: RW semaphore counter constants.  */
-#ifndef _SPARC64_RWSEM_CONST_H
-#define _SPARC64_RWSEM_CONST_H
-
-#define RWSEM_UNLOCKED_VALUE           0x00000000
-#define RWSEM_ACTIVE_BIAS              0x00000001
-#define RWSEM_ACTIVE_MASK              0x0000ffff
-#define RWSEM_WAITING_BIAS             (-0x00010000)
-#define RWSEM_ACTIVE_READ_BIAS         RWSEM_ACTIVE_BIAS
-#define RWSEM_ACTIVE_WRITE_BIAS                (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
-
-#endif /* _SPARC64_RWSEM_CONST_H */
index 6e56210..a2b4302 100644 (file)
 
 #include <linux/list.h>
 #include <linux/spinlock.h>
-#include <asm/rwsem-const.h>
 
 struct rwsem_waiter;
 
 struct rw_semaphore {
-       signed int count;
-       spinlock_t              wait_lock;
-       struct list_head        wait_list;
+       signed long                     count;
+#define RWSEM_UNLOCKED_VALUE           0x00000000L
+#define RWSEM_ACTIVE_BIAS              0x00000001L
+#define RWSEM_ACTIVE_MASK              0xffffffffL
+#define RWSEM_WAITING_BIAS             (-RWSEM_ACTIVE_MASK-1)
+#define RWSEM_ACTIVE_READ_BIAS         RWSEM_ACTIVE_BIAS
+#define RWSEM_ACTIVE_WRITE_BIAS                (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+       spinlock_t                      wait_lock;
+       struct list_head                wait_list;
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
-       struct lockdep_map      dep_map;
+       struct lockdep_map              dep_map;
 #endif
 };
 
@@ -41,6 +46,11 @@ struct rw_semaphore {
 #define DECLARE_RWSEM(name) \
        struct rw_semaphore name = __RWSEM_INITIALIZER(name)
 
+extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
+
 extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
                         struct lock_class_key *key);
 
@@ -51,27 +61,103 @@ do {                                                               \
        __init_rwsem((sem), #sem, &__key);                      \
 } while (0)
 
-extern void __down_read(struct rw_semaphore *sem);
-extern int __down_read_trylock(struct rw_semaphore *sem);
-extern void __down_write(struct rw_semaphore *sem);
-extern int __down_write_trylock(struct rw_semaphore *sem);
-extern void __up_read(struct rw_semaphore *sem);
-extern void __up_write(struct rw_semaphore *sem);
-extern void __downgrade_write(struct rw_semaphore *sem);
+/*
+ * lock for reading
+ */
+static inline void __down_read(struct rw_semaphore *sem)
+{
+       if (unlikely(atomic64_inc_return((atomic64_t *)(&sem->count)) <= 0L))
+               rwsem_down_read_failed(sem);
+}
+
+static inline int __down_read_trylock(struct rw_semaphore *sem)
+{
+       long tmp;
+
+       while ((tmp = sem->count) >= 0L) {
+               if (tmp == cmpxchg(&sem->count, tmp,
+                                  tmp + RWSEM_ACTIVE_READ_BIAS)) {
+                       return 1;
+               }
+       }
+       return 0;
+}
 
+/*
+ * lock for writing
+ */
 static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
 {
-       __down_write(sem);
+       long tmp;
+
+       tmp = atomic64_add_return(RWSEM_ACTIVE_WRITE_BIAS,
+                                 (atomic64_t *)(&sem->count));
+       if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
+               rwsem_down_write_failed(sem);
 }
 
-static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
+static inline void __down_write(struct rw_semaphore *sem)
 {
-       return atomic_add_return(delta, (atomic_t *)(&sem->count));
+       __down_write_nested(sem, 0);
+}
+
+static inline int __down_write_trylock(struct rw_semaphore *sem)
+{
+       long tmp;
+
+       tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
+                     RWSEM_ACTIVE_WRITE_BIAS);
+       return tmp == RWSEM_UNLOCKED_VALUE;
 }
 
-static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
+/*
+ * unlock after reading
+ */
+static inline void __up_read(struct rw_semaphore *sem)
+{
+       long tmp;
+
+       tmp = atomic64_dec_return((atomic64_t *)(&sem->count));
+       if (unlikely(tmp < -1L && (tmp & RWSEM_ACTIVE_MASK) == 0L))
+               rwsem_wake(sem);
+}
+
+/*
+ * unlock after writing
+ */
+static inline void __up_write(struct rw_semaphore *sem)
+{
+       if (unlikely(atomic64_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
+                                        (atomic64_t *)(&sem->count)) < 0L))
+               rwsem_wake(sem);
+}
+
+/*
+ * implement atomic add functionality
+ */
+static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
+{
+       atomic64_add(delta, (atomic64_t *)(&sem->count));
+}
+
+/*
+ * downgrade write lock to read lock
+ */
+static inline void __downgrade_write(struct rw_semaphore *sem)
+{
+       long tmp;
+
+       tmp = atomic64_add_return(-RWSEM_WAITING_BIAS, (atomic64_t *)(&sem->count));
+       if (tmp < 0L)
+               rwsem_downgrade_wake(sem);
+}
+
+/*
+ * implement exchange and add functionality
+ */
+static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
 {
-       atomic_add(delta, (atomic_t *)(&sem->count));
+       return atomic64_add_return(delta, (atomic64_t *)(&sem->count));
 }
 
 static inline int rwsem_is_locked(struct rw_semaphore *sem)
index c4b5e03..846d1c4 100644 (file)
@@ -15,7 +15,7 @@ lib-$(CONFIG_SPARC32) += divdi3.o udivdi3.o
 lib-$(CONFIG_SPARC32) += copy_user.o locks.o
 lib-y                 += atomic_$(BITS).o
 lib-$(CONFIG_SPARC32) += lshrdi3.o ashldi3.o
-lib-y                 += rwsem_$(BITS).o
+lib-$(CONFIG_SPARC32) += rwsem_32.o
 lib-$(CONFIG_SPARC32) += muldi3.o bitext.o cmpdi2.o
 
 lib-$(CONFIG_SPARC64) += copy_page.o clear_page.o bzero.o
diff --git a/arch/sparc/lib/rwsem_64.S b/arch/sparc/lib/rwsem_64.S
deleted file mode 100644 (file)
index 91a7d29..0000000
+++ /dev/null
@@ -1,163 +0,0 @@
-/* rwsem.S: RW semaphore assembler.
- *
- * Written by David S. Miller (davem@redhat.com), 2001.
- * Derived from asm-i386/rwsem.h
- */
-
-#include <asm/rwsem-const.h>
-
-       .section        .sched.text, "ax"
-
-       .globl          __down_read
-__down_read:
-1:     lduw            [%o0], %g1
-       add             %g1, 1, %g7
-       cas             [%o0], %g1, %g7
-       cmp             %g1, %g7
-       bne,pn          %icc, 1b
-        add            %g7, 1, %g7
-       cmp             %g7, 0
-       bl,pn           %icc, 3f
-        nop
-2:
-       retl
-        nop
-3:
-       save            %sp, -192, %sp
-       call            rwsem_down_read_failed
-        mov            %i0, %o0
-       ret
-        restore
-       .size           __down_read, .-__down_read
-
-       .globl          __down_read_trylock
-__down_read_trylock:
-1:     lduw            [%o0], %g1
-       add             %g1, 1, %g7
-       cmp             %g7, 0
-       bl,pn           %icc, 2f
-        mov            0, %o1
-       cas             [%o0], %g1, %g7
-       cmp             %g1, %g7
-       bne,pn          %icc, 1b
-        mov            1, %o1
-2:     retl
-        mov            %o1, %o0
-       .size           __down_read_trylock, .-__down_read_trylock
-
-       .globl          __down_write
-__down_write:
-       sethi           %hi(RWSEM_ACTIVE_WRITE_BIAS), %g1
-       or              %g1, %lo(RWSEM_ACTIVE_WRITE_BIAS), %g1
-1:
-       lduw            [%o0], %g3
-       add             %g3, %g1, %g7
-       cas             [%o0], %g3, %g7
-       cmp             %g3, %g7
-       bne,pn          %icc, 1b
-        cmp            %g7, 0
-       bne,pn          %icc, 3f
-        nop
-2:     retl
-        nop
-3:
-       save            %sp, -192, %sp
-       call            rwsem_down_write_failed
-        mov            %i0, %o0
-       ret
-        restore
-       .size           __down_write, .-__down_write
-
-       .globl          __down_write_trylock
-__down_write_trylock:
-       sethi           %hi(RWSEM_ACTIVE_WRITE_BIAS), %g1
-       or              %g1, %lo(RWSEM_ACTIVE_WRITE_BIAS), %g1
-1:
-       lduw            [%o0], %g3
-       cmp             %g3, 0
-       bne,pn          %icc, 2f
-        mov            0, %o1
-       add             %g3, %g1, %g7
-       cas             [%o0], %g3, %g7
-       cmp             %g3, %g7
-       bne,pn          %icc, 1b
-        mov            1, %o1
-2:     retl
-        mov            %o1, %o0
-       .size           __down_write_trylock, .-__down_write_trylock
-
-       .globl          __up_read
-__up_read:
-1:
-       lduw            [%o0], %g1
-       sub             %g1, 1, %g7
-       cas             [%o0], %g1, %g7
-       cmp             %g1, %g7
-       bne,pn          %icc, 1b
-        cmp            %g7, 0
-       bl,pn           %icc, 3f
-        nop
-2:     retl
-        nop
-3:     sethi           %hi(RWSEM_ACTIVE_MASK), %g1
-       sub             %g7, 1, %g7
-       or              %g1, %lo(RWSEM_ACTIVE_MASK), %g1
-       andcc           %g7, %g1, %g0
-       bne,pn          %icc, 2b
-        nop
-       save            %sp, -192, %sp
-       call            rwsem_wake
-        mov            %i0, %o0
-       ret
-        restore
-       .size           __up_read, .-__up_read
-
-       .globl          __up_write
-__up_write:
-       sethi           %hi(RWSEM_ACTIVE_WRITE_BIAS), %g1
-       or              %g1, %lo(RWSEM_ACTIVE_WRITE_BIAS), %g1
-1:
-       lduw            [%o0], %g3
-       sub             %g3, %g1, %g7
-       cas             [%o0], %g3, %g7
-       cmp             %g3, %g7
-       bne,pn          %icc, 1b
-        sub            %g7, %g1, %g7
-       cmp             %g7, 0
-       bl,pn           %icc, 3f
-        nop
-2:
-       retl
-        nop
-3:
-       save            %sp, -192, %sp
-       call            rwsem_wake
-        mov            %i0, %o0
-       ret
-        restore
-       .size           __up_write, .-__up_write
-
-       .globl          __downgrade_write
-__downgrade_write:
-       sethi           %hi(RWSEM_WAITING_BIAS), %g1
-       or              %g1, %lo(RWSEM_WAITING_BIAS), %g1
-1:
-       lduw            [%o0], %g3
-       sub             %g3, %g1, %g7
-       cas             [%o0], %g3, %g7
-       cmp             %g3, %g7
-       bne,pn          %icc, 1b
-        sub            %g7, %g1, %g7
-       cmp             %g7, 0
-       bl,pn           %icc, 3f
-        nop
-2:
-       retl
-        nop
-3:
-       save            %sp, -192, %sp
-       call            rwsem_downgrade_wake
-        mov            %i0, %o0
-       ret
-        restore
-       .size           __downgrade_write, .-__downgrade_write