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use __always_inline for __xchg

PATCH In review Imre Kaloz 2 participants 2 messages Jan 28, 2006 – Nov 24, 2009 MIPS

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Imre Kaloz

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#0 lore raw

PATCH 1/1 use __always_inline for __xchg

The following patch changes inline for __xchg to __always_inline in include/asm-mips/system.h, following the changes in git. Without this change linking the kernel fails.

Signed-off-by Imre Kaloz <[email protected]>
Signed-off-by Felix Fietkau <[email protected]>
include/asm-mips/system.h +1 -1
@@ -273,7 +273,7 @@
    if something tries to do an invalid xchg().  */
 extern void __xchg_called_with_bad_pointer(void);
 
-static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int size)
+static __always_inline unsigned long __xchg(unsigned long x, volatile void * ptr, int size)
 {
 	switch (size) {
 		case 4:
#1 lore raw
Quoted 6 lines · Imre Kaloz

The following patch changes inline for __xchg to __always_inline in include/asm-mips/system.h, following the changes in git. Without this change linking the kernel fails.

Signed-off-by Imre Kaloz <[email protected]>
Signed-off-by Felix Fietkau <[email protected]>

Imre just pointed me at this antique patch again saying it was still needed. Back then I ditched it because I couldn't see what the problem it was trying to fix was - but after a little brainstorming it got obvious.

Now I don't like __always_inline which forces the optimizer to do things which may not really be what we want, for example when building with -Os so I found a different fix using BUILD_BUG_ON(). Patch below.

Cheers,

Ralf

From: Ralf Baechle <[email protected]>

MIPS: Fix build error if __xchg() is not getting inlined.

If __xchg() is not getting inlined the outline version of the function will have a reference to __xchg_called_with_bad_pointer() which does not exist remaining. Fixed by using BUILD_BUG_ON() xchg() to check for allowable operand sizes.

Signed-off-by Ralf Baechle <[email protected]>
arch/mips/include/asm/system.h +8 -6
index fcf5f98..587a48a 100644
@@ -193,10 +193,6 @@ extern __u64 __xchg_u64_unsupported_on_32bit_kernels(volatile __u64 * m, __u64 v
 #define __xchg_u64 __xchg_u64_unsupported_on_32bit_kernels
 #endif
 
-/* This function doesn't exist, so you'll get a linker error
-   if something tries to do an invalid xchg().  */
-extern void __xchg_called_with_bad_pointer(void);
-
 static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int size)
 {
 	switch (size) {

@@ -205,11 +201,17 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz
 	case 8:
 		return __xchg_u64(ptr, x);
 	}
-	__xchg_called_with_bad_pointer();
+
 	return x;
 }
 
-#define xchg(ptr, x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x), (ptr), sizeof(*(ptr))))
+#define xchg(ptr, x)							\
+({									\
+	BUILD_BUG_ON(sizeof(*(ptr)) & ~0xc);				\
+									\
+	((__typeof__(*(ptr)))						\
+		__xchg((unsigned long)(x), (ptr), sizeof(*(ptr))));	\
+})
 
 extern void set_handler(unsigned long offset, void *addr, unsigned long len);
 extern void set_uncached_handler(unsigned long offset, void *addr, unsigned long len);