Ticket spinlocks for flare based on Bjoern's old code.

2 files changed, 44 insertions, 53 deletions

diff --git a/arch/sparc/include/asm/spinlock_64.h b/arch/sparc/include/asm/spinlock_64.h
index 073936a8b275..0415e1867e92 100644
--- a/arch/sparc/include/asm/spinlock_64.h
+++ b/arch/sparc/include/asm/spinlock_64.h
@@ -13,82 +13,72 @@
  * and rebuild your kernel.
  */
 
-/* Because we play games to save cycles in the non-contention case, we
- * need to be extra careful about branch targets into the "spinning"
- * code.  They live in their own section, but the newer V9 branches
- * have a shorter range than the traditional 32-bit sparc branch
- * variants.  The rule is that the branches that go into and out of
- * the spinner sections must be pre-V9 branches.
- */
-
-#define arch_spin_is_locked(lp) ((lp)->lock != 0)
+#define arch_spin_is_locked(lp) ((lp)->tail != (lp)->head)
 
 #define arch_spin_unlock_wait(lp)       \
         do {    rmb();                  \
-        } while((lp)->lock)
+        } while((lp)->tail != (lp)->head)
 
 static inline void arch_spin_lock(arch_spinlock_t *lock)
 {
-        unsigned long tmp;
+        int ticket, tmp;
 
         __asm__ __volatile__(
-"1:     ldstub          [%1], %0\n"
-"       brnz,pn         %0, 2f\n"
-"        nop\n"
-"       .subsection     2\n"
-"2:     ldub            [%1], %0\n"
-"       brnz,pt         %0, 2b\n"
-"        nop\n"
-"       ba,a,pt         %%xcc, 1b\n"
-"       .previous"
-        : "=&r" (tmp)
-        : "r" (lock)
+"1:     lduw            [%2], %0 \n" /* read ticket */
+"       add             %0, 1, %1 \n"
+"       cas             [%2], %0, %1 \n"
+"       cmp             %0, %1 \n"
+"       be,a,pt         %%icc, 2f \n"
+"        nop \n"
+"       ba              1b\n"
+"        nop \n"
+"2:     lduw            [%3], %1 \n"
+"       cmp             %0, %1 \n"
+"       be,a,pt         %%icc, 3f \n"
+"        nop \n"
+"       ba              2b\n"
+"3:      nop"
+        : "=&r" (ticket), "=&r" (tmp)
+        : "r" (&lock->tail), "r" (&lock->head)
         : "memory");
 }
 
 static inline int arch_spin_trylock(arch_spinlock_t *lock)
 {
-        unsigned long result;
-
+        int tail, head;
         __asm__ __volatile__(
-"       ldstub          [%1], %0\n"
-        : "=r" (result)
-        : "r" (lock)
+"       lduw            [%2], %0 \n" /* read tail */
+"       lduw            [%3], %1 \n" /* read head */
+"       cmp             %0, %1 \n"
+"       bne,a,pn        %%icc, 1f \n"
+"        nop \n"
+"       inc             %1 \n"
+"       cas             [%2], %0, %1 \n" /* try to inc ticket */
+"1:     "
+        : "=&r" (tail), "=&r" (head)
+        : "r" (&lock->tail), "r" (&lock->head)
         : "memory");
 
-        return (result == 0UL);
+        return (tail == head);
 }
 
 static inline void arch_spin_unlock(arch_spinlock_t *lock)
 {
+        int tmp;
         __asm__ __volatile__(
-"       stb             %%g0, [%0]"
-        : /* No outputs */
-        : "r" (lock)
+"       lduw            [%1], %0 \n"
+"       inc             %0 \n"
+"       st              %0, [%1] \n"
+        : "=&r" (tmp)
+        : "r" (&lock->head)
         : "memory");
 }
 
-static inline void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
-{
-        unsigned long tmp1, tmp2;
+/* We don't handle this yet, but it looks like not re-enabling the interrupts
+ * works fine, too. For example, lockdep also does it like this.
+ */
+#define arch_spin_lock_flags(l, f) arch_spin_lock(l)
 
-        __asm__ __volatile__(
-"1:     ldstub          [%2], %0\n"
-"       brnz,pn         %0, 2f\n"
-"        nop\n"
-"       .subsection     2\n"
-"2:     rdpr            %%pil, %1\n"
-"       wrpr            %3, %%pil\n"
-"3:     ldub            [%2], %0\n"
-"       brnz,pt         %0, 3b\n"
-"        nop\n"
-"       ba,pt           %%xcc, 1b\n"
-"        wrpr           %1, %%pil\n"
-"       .previous"
-        : "=&r" (tmp1), "=&r" (tmp2)
-        : "r"(lock), "r"(flags)
-        : "memory");
-}
 
 /* Multi-reader locks, these are much saner than the 32-bit Sparc ones... */
 
diff --git a/arch/sparc/include/asm/spinlock_types.h b/arch/sparc/include/asm/spinlock_types.h
index 9c454fdeaad8..49b89fe2ccfc 100644
--- a/arch/sparc/include/asm/spinlock_types.h
+++ b/arch/sparc/include/asm/spinlock_types.h
@@ -6,10 +6,11 @@
 #endif
 
 typedef struct {
-        volatile unsigned char lock;
+        volatile int tail;
+        volatile int head;
 } arch_spinlock_t;
 
-#define __ARCH_SPIN_LOCK_UNLOCKED       { 0 }
+#define __ARCH_SPIN_LOCK_UNLOCKED       { 0, 0 }
 
 typedef struct {
         volatile unsigned int lock;