kprobes: Make hash_64() as always inlined

Because hash_64() is called from the get_kprobe() inside
int3 handler, kernel causes int3 recursion and crashes if
kprobes user puts a probe on it.

Usually hash_64() is inlined into caller function, but in
some cases, it has instances by gcc's interprocedural
constant propagation.

This patch uses __always_inline instead of inline to
prevent gcc from doing such things.

Reported-by: Timo Juhani Lindfors <timo.lindfors@iki.fi>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Nadia Yvette Chambers <nyc@holomorphy.com>
Cc: yrl.pp-manager.tt@hitachi.com
Cc: David S. Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20130314115230.19690.39387.stgit@mhiramat-M0-7522
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/hash.h

@@ -15,6 +15,7 @@
  */
 
 #include <asm/types.h>
+#include <linux/compiler.h>
 
 /* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */
 #define GOLDEN_RATIO_PRIME_32 0x9e370001UL
@@ -31,7 +32,7 @@
 #error Wordsize not 32 or 64
 #endif
 
-static inline u64 hash_64(u64 val, unsigned int bits)
+static __always_inline u64 hash_64(u64 val, unsigned int bits)
 {
 	u64 hash = val;