alpha: fix percpu build breakage

alpha percpu access requires custom SHIFT_PERCPU_PTR() definition for
modules to work around addressing range limitation.  This is done via
generating inline assembly using C preprocessing which forces the
assembler to generate external reference.  This happens behind the
compiler's back and makes the compiler think that static percpu variables
in modules are unused.

This used to be worked around by using __unused attribute for percpu
variables which prevent the compiler from omitting the variable; however,
recent declare/definition attribute unification change broke this as
__used can't be used for declaration.  Also, in the process,
PER_CPU_ATTRIBUTES definition in alpha percpu.h got broken.

This patch adds PER_CPU_DEF_ATTRIBUTES which is only used for definitions
and make alpha use it to add __used for percpu variables in modules.  This
also fixes the PER_CPU_ATTRIBUTES double definition bug.

Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: maximilian attems <max@stro.at>
Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/arch/alpha/include/asm/percpu.h b/arch/alpha/include/asm/percpu.h
index 06c5c7a4afd3..b663f1f10b6a 100644
--- a/arch/alpha/include/asm/percpu.h
+++ b/arch/alpha/include/asm/percpu.h
@@ -30,7 +30,7 @@ extern unsigned long __per_cpu_offset[NR_CPUS];
 
 #ifndef MODULE
 #define SHIFT_PERCPU_PTR(var, offset) RELOC_HIDE(&per_cpu_var(var), (offset))
-#define PER_CPU_ATTRIBUTES
+#define PER_CPU_DEF_ATTRIBUTES
 #else
 /*
  * To calculate addresses of locally defined variables, GCC uses 32-bit
@@ -49,7 +49,7 @@ extern unsigned long __per_cpu_offset[NR_CPUS];
                 : "=&r"(__ptr), "=&r"(tmp_gp));         \
         (typeof(&per_cpu_var(var)))(__ptr + (offset)); })
 
-#define PER_CPU_ATTRIBUTES      __used
+#define PER_CPU_DEF_ATTRIBUTES  __used
 
 #endif /* MODULE */
 
@@ -71,7 +71,7 @@ extern unsigned long __per_cpu_offset[NR_CPUS];
 #define __get_cpu_var(var)              per_cpu_var(var)
 #define __raw_get_cpu_var(var)          per_cpu_var(var)
 
-#define PER_CPU_ATTRIBUTES
+#define PER_CPU_DEF_ATTRIBUTES
 
 #endif /* SMP */