From: Paolo 'Blaisorblade' Giarrusso <[email protected]>
i386 enables the xchg based implementation of r/w semaphores for any processor
as good as 486. So it was quite interesting to see x86_64 never using it! And it
was even more interesting to see, in rwsem.h:
/* rwsem.h: R/W semaphores implemented using XADD/CMPXCHG for x86_64+
*
* Written by David Howells ([email protected]).
* Ported by Andi Kleen <[email protected]> to x86-64.
I.e. the implementation was written, is present in the tree, but due to this:
#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
#include <linux/rwsem-spinlock.h> /* use a generic implementation */
#else
#include <asm/rwsem.h> /* use an arch-specific implementation */
#endif
it was probably _NEVER_ compiled!!!
So, handle with care this one-liner, and test it properly.
CC: Andi Kleen <[email protected]>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[email protected]>
---
arch/x86_64/Kconfig | 5 ++---
1 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -39,11 +39,10 @@ config SBUS
bool
config RWSEM_GENERIC_SPINLOCK
- bool
- default y
+ def_bool n
config RWSEM_XCHGADD_ALGORITHM
- bool
+ def_bool y
config GENERIC_CALIBRATE_DELAY
bool
-
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