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x86/percpu: Clean up <asm/percpu.h> a bit
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 - 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 <mingo@kernel.org>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
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Ingo Molnar committed May 20, 2024
1 parent 47c9dbd commit 61d73e4
Showing 1 changed file with 50 additions and 41 deletions.
91 changes: 50 additions & 41 deletions arch/x86/include/asm/percpu.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand All @@ -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)":"
Expand Down Expand Up @@ -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 ""
Expand All @@ -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.
*
Expand All @@ -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
Expand Down Expand Up @@ -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) \
({ \
Expand All @@ -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; })
Expand Down Expand Up @@ -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) \
Expand Down Expand Up @@ -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) \
({ \
Expand All @@ -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) \
({ \
Expand Down Expand Up @@ -314,6 +317,7 @@ do { \
})

#if defined(CONFIG_X86_32) && !defined(CONFIG_UML)

#define percpu_cmpxchg64_op(size, qual, _var, _oval, _nval) \
({ \
union { \
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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.
Expand Down Expand Up @@ -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

Expand All @@ -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 */

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