tile: support atomic64_dec_if_positive()

Use the normal cmpxchg() idiom to implement this functionality.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index 0e500d9..9a9d086 100644 (file)
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -24,6 +24,7 @@ config TILE
        select MODULES_USE_ELF_RELA
        select HAVE_ARCH_TRACEHOOK
        select HAVE_SYSCALL_TRACEPOINTS
+       select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 
 # FIXME: investigate whether we need/want these options.
 #      select HAVE_IOREMAP_PROT

diff --git a/arch/tile/include/asm/atomic.h b/arch/tile/include/asm/atomic.h
index f246142..e71387a 100644 (file)
--- a/arch/tile/include/asm/atomic.h
+++ b/arch/tile/include/asm/atomic.h
@@ -131,4 +131,25 @@ static inline int atomic_read(const atomic_t *v)
 #include <asm/atomic_64.h>
 #endif
 
+#ifndef __ASSEMBLY__
+
+static inline long long atomic64_dec_if_positive(atomic64_t *v)
+{
+       long long c, old, dec;
+
+       c = atomic64_read(v);
+       for (;;) {
+               dec = c - 1;
+               if (unlikely(dec < 0))
+                       break;
+               old = atomic64_cmpxchg((v), c, dec);
+               if (likely(old == c))
+                       break;
+               c = old;
+       }
+       return dec;
+}
+
+#endif /* __ASSEMBLY__ */
+
 #endif /* _ASM_TILE_ATOMIC_H */