x86/percpu: Clean up <asm/percpu.h> a bit

 - Fix misc typos

 - There's 4 variants of the same spelling right now:

     'per-CPU', 'per CPU', 'percpu' and 'per-cpu'

   Standardize on 'per-CPU' only.

 - s/makes gcc load
    /makes the compiler load

 - Instead of:

     #ifdef CONFIG_XXXX
     #define YYYY FOO
     #else
     #define YYYY BAR
     #endif

   Use the slightly more readable form of:

     #ifdef CONFIG_XXXX
     # define YYYY FOO
     #else
     # define YYYY BAR
     #endif

 - Standardize & expand '#else' and '#endif' comments

 - Fix comment style

 - Capitalize x86 instruction names in comments

No change in code.

Signed-off-by: Ingo Molnar <[email protected]>
Cc: Uros Bizjak <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: [email protected]

Author: Ingo Molnar

arch/x86/include/asm/percpu.h

@@ -3,30 +3,30 @@
 #define _ASM_X86_PERCPU_H
 
 #ifdef CONFIG_X86_64
-#define __percpu_seg		gs
-#define __percpu_rel		(%rip)
+# define __percpu_seg		gs
+# define __percpu_rel		(%rip)
 #else
-#define __percpu_seg		fs
-#define __percpu_rel
+# define __percpu_seg		fs
+# define __percpu_rel
 #endif
 
 #ifdef __ASSEMBLY__
 
 #ifdef CONFIG_SMP
-#define __percpu		%__percpu_seg:
+# define __percpu		%__percpu_seg:
 #else
-#define __percpu
+# define __percpu
 #endif
 
 #define PER_CPU_VAR(var)	__percpu(var)__percpu_rel
 
 #ifdef CONFIG_X86_64_SMP
-#define INIT_PER_CPU_VAR(var)  init_per_cpu__##var
+# define INIT_PER_CPU_VAR(var)  init_per_cpu__##var
 #else
-#define INIT_PER_CPU_VAR(var)  var
+# define INIT_PER_CPU_VAR(var)  var
 #endif
 
-#else /* ...!ASSEMBLY */
+#else /* !__ASSEMBLY__: */
 
 #include <linux/build_bug.h>
 #include <linux/stringify.h>
@@ -37,19 +37,19 @@
 #ifdef CONFIG_CC_HAS_NAMED_AS
 
 #ifdef __CHECKER__
-#define __seg_gs		__attribute__((address_space(__seg_gs)))
-#define __seg_fs		__attribute__((address_space(__seg_fs)))
+# define __seg_gs		__attribute__((address_space(__seg_gs)))
+# define __seg_fs		__attribute__((address_space(__seg_fs)))
 #endif
 
 #ifdef CONFIG_X86_64
-#define __percpu_seg_override	__seg_gs
+# define __percpu_seg_override	__seg_gs
 #else
-#define __percpu_seg_override	__seg_fs
+# define __percpu_seg_override	__seg_fs
 #endif
 
 #define __percpu_prefix		""
 
-#else /* CONFIG_CC_HAS_NAMED_AS */
+#else /* !CONFIG_CC_HAS_NAMED_AS: */
 
 #define __percpu_seg_override
 #define __percpu_prefix		"%%"__stringify(__percpu_seg)":"
@@ -80,7 +80,8 @@
 
 #define PER_CPU_VAR(var)	%__percpu_seg:(var)__percpu_rel
 
-#else /* CONFIG_SMP */
+#else /* !CONFIG_SMP: */
+
 #define __percpu_seg_override
 #define __percpu_prefix		""
 #define __force_percpu_prefix	""
@@ -96,7 +97,7 @@
 #define __force_percpu_arg(x)	__force_percpu_prefix "%" #x
 
 /*
- * Initialized pointers to per-cpu variables needed for the boot
+ * Initialized pointers to per-CPU variables needed for the boot
  * processor need to use these macros to get the proper address
  * offset from __per_cpu_load on SMP.
  *
@@ -106,13 +107,15 @@
        extern typeof(var) init_per_cpu_var(var)
 
 #ifdef CONFIG_X86_64_SMP
-#define init_per_cpu_var(var)  init_per_cpu__##var
+# define init_per_cpu_var(var)  init_per_cpu__##var
 #else
-#define init_per_cpu_var(var)  var
+# define init_per_cpu_var(var)  var
 #endif
 
-/* For arch-specific code, we can use direct single-insn ops (they
- * don't give an lvalue though). */
+/*
+ * For arch-specific code, we can use direct single-insn ops (they
+ * don't give an lvalue though).
+ */
 
 #define __pcpu_type_1 u8
 #define __pcpu_type_2 u16
@@ -158,7 +161,7 @@ do {									\
 
 #define __raw_cpu_read_const(pcp)	__raw_cpu_read(, , pcp)
 
-#else /* CONFIG_USE_X86_SEG_SUPPORT */
+#else /* !CONFIG_USE_X86_SEG_SUPPORT: */
 
 #define __raw_cpu_read(size, qual, _var)				\
 ({									\
@@ -183,7 +186,7 @@ do {									\
 } while (0)
 
 /*
- * The generic per-cpu infrastrucutre is not suitable for
+ * The generic per-CPU infrastrucutre is not suitable for
  * reading const-qualified variables.
  */
 #define __raw_cpu_read_const(pcp)	({ BUILD_BUG(); (typeof(pcp))0; })
@@ -219,7 +222,7 @@ do {									\
 } while (0)
 
 /*
- * Generate a percpu add to memory instruction and optimize code
+ * Generate a per-CPU add to memory instruction and optimize code
  * if one is added or subtracted.
  */
 #define percpu_add_op(size, qual, var, val)				\
@@ -266,9 +269,9 @@ do {									\
 })
 
 /*
- * this_cpu_xchg() is implemented using cmpxchg without a lock prefix.
- * xchg is expensive due to the implied lock prefix. The processor
- * cannot prefetch cachelines if xchg is used.
+ * this_cpu_xchg() is implemented using CMPXCHG without a LOCK prefix.
+ * XCHG is expensive due to the implied LOCK prefix. The processor
+ * cannot prefetch cachelines if XCHG is used.
  */
 #define this_percpu_xchg_op(_var, _nval)				\
 ({									\
@@ -278,8 +281,8 @@ do {									\
 })
 
 /*
- * cmpxchg has no such implied lock semantics as a result it is much
- * more efficient for cpu local operations.
+ * CMPXCHG has no such implied lock semantics as a result it is much
+ * more efficient for CPU-local operations.
  */
 #define percpu_cmpxchg_op(size, qual, _var, _oval, _nval)		\
 ({									\
@@ -314,6 +317,7 @@ do {									\
 })
 
 #if defined(CONFIG_X86_32) && !defined(CONFIG_UML)
+
 #define percpu_cmpxchg64_op(size, qual, _var, _oval, _nval)		\
 ({									\
 	union {								\
@@ -374,7 +378,8 @@ do {									\
 
 #define raw_cpu_try_cmpxchg64(pcp, ovalp, nval)		percpu_try_cmpxchg64_op(8,         , pcp, ovalp, nval)
 #define this_cpu_try_cmpxchg64(pcp, ovalp, nval)	percpu_try_cmpxchg64_op(8, volatile, pcp, ovalp, nval)
-#endif
+
+#endif /* defined(CONFIG_X86_32) && !defined(CONFIG_UML) */
 
 #ifdef CONFIG_X86_64
 #define raw_cpu_cmpxchg64(pcp, oval, nval)	percpu_cmpxchg_op(8,         , pcp, oval, nval);
@@ -443,7 +448,8 @@ do {									\
 
 #define raw_cpu_try_cmpxchg128(pcp, ovalp, nval)	percpu_try_cmpxchg128_op(16,         , pcp, ovalp, nval)
 #define this_cpu_try_cmpxchg128(pcp, ovalp, nval)	percpu_try_cmpxchg128_op(16, volatile, pcp, ovalp, nval)
-#endif
+
+#endif /* CONFIG_X86_64 */
 
 #define raw_cpu_read_1(pcp)		__raw_cpu_read(1, , pcp)
 #define raw_cpu_read_2(pcp)		__raw_cpu_read(2, , pcp)
@@ -510,8 +516,8 @@ do {									\
 #define this_cpu_try_cmpxchg_4(pcp, ovalp, nval)	percpu_try_cmpxchg_op(4, volatile, pcp, ovalp, nval)
 
 /*
- * Per cpu atomic 64 bit operations are only available under 64 bit.
- * 32 bit must fall back to generic operations.
+ * Per-CPU atomic 64-bit operations are only available under 64-bit kernels.
+ * 32-bit kernels must fall back to generic operations.
  */
 #ifdef CONFIG_X86_64
 #define raw_cpu_read_8(pcp)		__raw_cpu_read(8, , pcp)
@@ -539,20 +545,23 @@ do {									\
 #define this_cpu_try_cmpxchg_8(pcp, ovalp, nval)	percpu_try_cmpxchg_op(8, volatile, pcp, ovalp, nval)
 
 #define raw_cpu_read_long(pcp)		raw_cpu_read_8(pcp)
-#else
-/* There is no generic 64 bit read stable operation for 32 bit targets. */
+
+#else /* !CONFIG_X86_64: */
+
+/* There is no generic 64-bit read stable operation for 32-bit targets. */
 #define this_cpu_read_stable_8(pcp)	({ BUILD_BUG(); (typeof(pcp))0; })
 
 #define raw_cpu_read_long(pcp)		raw_cpu_read_4(pcp)
-#endif
+
+#endif /* CONFIG_X86_64 */
 
 #define this_cpu_read_const(pcp)	__raw_cpu_read_const(pcp)
 
 /*
- * this_cpu_read() makes gcc load the percpu variable every time it is
- * accessed while this_cpu_read_stable() allows the value to be cached.
+ * this_cpu_read() makes the compiler load the per-CPU variable every time
+ * it is accessed while this_cpu_read_stable() allows the value to be cached.
  * this_cpu_read_stable() is more efficient and can be used if its value
- * is guaranteed to be valid across cpus.  The current users include
+ * is guaranteed to be valid across CPUs.  The current users include
  * pcpu_hot.current_task and pcpu_hot.top_of_stack, both of which are
  * actually per-thread variables implemented as per-CPU variables and
  * thus stable for the duration of the respective task.
@@ -626,12 +635,12 @@ DECLARE_PER_CPU_READ_MOSTLY(unsigned long, this_cpu_off);
 
 #define	early_per_cpu_ptr(_name) (_name##_early_ptr)
 #define	early_per_cpu_map(_name, _idx) (_name##_early_map[_idx])
-#define	early_per_cpu(_name, _cpu) 				\
+#define	early_per_cpu(_name, _cpu)				\
 	*(early_per_cpu_ptr(_name) ?				\
 		&early_per_cpu_ptr(_name)[_cpu] :		\
 		&per_cpu(_name, _cpu))
 
-#else	/* !CONFIG_SMP */
+#else /* !CONFIG_SMP: */
 #define	DEFINE_EARLY_PER_CPU(_type, _name, _initvalue)		\
 	DEFINE_PER_CPU(_type, _name) = _initvalue
 
@@ -651,6 +660,6 @@ DECLARE_PER_CPU_READ_MOSTLY(unsigned long, this_cpu_off);
 #define	early_per_cpu_ptr(_name) NULL
 /* no early_per_cpu_map() */
 
-#endif	/* !CONFIG_SMP */
+#endif /* CONFIG_SMP */
 
 #endif /* _ASM_X86_PERCPU_H */