Use the normal cmpxchg() idiom to implement this functionality.
Signed-off-by: Chris Metcalf <[email protected]>
---
arch/tile/Kconfig | 1 +
arch/tile/include/asm/atomic.h | 21 +++++++++++++++++++++
2 files changed, 22 insertions(+)
diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index 1bb7ad4..0a7b7da 100644
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -21,6 +21,7 @@ config TILE
select ARCH_HAVE_NMI_SAFE_CMPXCHG
select GENERIC_CLOCKEVENTS
select MODULES_USE_ELF_RELA
+ 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
--- 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 */
--
1.7.10.3
--
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