[Minios-devel] [UNIKRAFT PATCH 2/4] include/uk: fix test_bit atomicity

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

ukarch_test_bit_sync does not make sense. A barrier() call is not a
memory barrier as was said in the comment. Even if it it was, it would
not make ukarch_test_bit_sync atomic. In fact this "barrier()" call is
needed in ukarch_test_bit, and does not help ukarch_test_bit_sync to
become a "sync" version.

This commit merges these two function together, and adds a missing
uk_test_bit into bitops.h.

Signed-off-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>
---
 include/uk/arch/atomic.h | 14 +++-----------
 include/uk/bitops.h      |  1 +
 2 files changed, 4 insertions(+), 11 deletions(-)

diff --git a/include/uk/arch/atomic.h b/include/uk/arch/atomic.h
index 0964e14..e6444c0 100644
--- a/include/uk/arch/atomic.h
+++ b/include/uk/arch/atomic.h
@@ -127,8 +127,10 @@ static inline int ukarch_test_bit(unsigned int nr,
                                        const volatile unsigned long *byte)
 {
        const volatile __u8 *ptr = (const __u8 *)byte;
+       int ret =  ((1 << (nr & 7)) & (ptr[nr >> 3])) != 0;
 
-       return ((1 << (nr & 7)) & (ptr[nr >> 3])) != 0;
+       barrier();
+       return ret;
 }
 
 /**
@@ -188,16 +190,6 @@ static inline void ukarch_clr_bit_sync(unsigned int nr, 
volatile void *byte)
        ukarch_test_and_clr_bit_sync(nr, byte);
 }
 
-/* As test_bit, but with a following memory barrier. */
-static inline int ukarch_test_bit_sync(unsigned int nr, volatile void *byte)
-{
-       int result;
-
-       result = ukarch_test_bit(nr, byte);
-       barrier();
-       return result;
-}
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/include/uk/bitops.h b/include/uk/bitops.h
index e004fdf..5a28410 100644
--- a/include/uk/bitops.h
+++ b/include/uk/bitops.h
@@ -250,6 +250,7 @@ uk_find_next_zero_bit(const unsigned long *addr, unsigned 
long size,
 #define uk_set_bit(i, a)          ukarch_set_bit_sync(i, a)
 #define __uk_clear_bit(i, a)      ukarch_clr_bit(i, a)
 #define uk_clear_bit(i, a)        ukarch_clr_bit_sync(i, a)
+#define uk_test_bit(i, a)         ukarch_test_bit(i, a)
 
 static inline int
 uk_test_and_clear_bit(long bit, volatile unsigned long *var)
-- 
2.19.0


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