From: Peter Zijlstra <[email protected]>
commit 7bd3e239d6c6d1cad276e8f130b386df4234dcd7 upstream.
The fact that volatile allows for atomic load/stores is a special case
not a requirement for {READ,WRITE}_ONCE(). Their primary purpose is to
force the compiler to emit load/stores _once_.
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Christian Borntraeger <[email protected]>
Acked-by: Will Deacon <[email protected]>
Acked-by: Linus Torvalds <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Paul McKenney <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
[wt: backported only for next patch]
Signed-off-by: Willy Tarreau <[email protected]>
---
include/linux/compiler.h | 16 ----------------
1 file changed, 16 deletions(-)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index c6d06e9..53563d8 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -181,29 +181,16 @@ void ftrace_likely_update(struct ftrace_branch_data *f,
int val, int expect);
#include <uapi/linux/types.h>
-static __always_inline void data_access_exceeds_word_size(void)
-#ifdef __compiletime_warning
-__compiletime_warning("data access exceeds word size and won't be atomic")
-#endif
-;
-
-static __always_inline void data_access_exceeds_word_size(void)
-{
-}
-
static __always_inline void __read_once_size(const volatile void *p, void
*res, int size)
{
switch (size) {
case 1: *(__u8 *)res = *(volatile __u8 *)p; break;
case 2: *(__u16 *)res = *(volatile __u16 *)p; break;
case 4: *(__u32 *)res = *(volatile __u32 *)p; break;
-#ifdef CONFIG_64BIT
case 8: *(__u64 *)res = *(volatile __u64 *)p; break;
-#endif
default:
barrier();
__builtin_memcpy((void *)res, (const void *)p, size);
- data_access_exceeds_word_size();
barrier();
}
}
@@ -214,13 +201,10 @@ static __always_inline void __write_once_size(volatile
void *p, void *res, int s
case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
-#ifdef CONFIG_64BIT
case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
-#endif
default:
barrier();
__builtin_memcpy((void *)p, (const void *)res, size);
- data_access_exceeds_word_size();
barrier();
}
}
--
2.8.0.rc2.1.gbe9624a
