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s390/percpu: Provide arch_this_cpu_read() implementation

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Provide an s390 specific implementation of arch_this_cpu_read() instead
of the generic variant. The generic variant uses preempt_disable() /
preempt_enable() pair and READ_ONCE().

Get rid of the preempt_disable() / preempt_enable() pairs by providing an
own variant which makes use of the new percpu code section infrastructure.

With this the text size of the kernel image is reduced by ~1k
(defconfig). Also 87 generated preempt_schedule_notrace() function
calls within the kernel image (modules not counted) are removed.

Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Heiko Carstens
2026-05-26 07:57:01 +02:00
committed by Alexander Gordeev
parent ee8cefbfb0
commit 9858c19a66
1 changed files with 31 additions and 0 deletions
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31
arch/s390/include/asm/percpu.h
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@@ -248,6 +248,37 @@ do { \
#endif /* MARCH_HAS_Z196_FEATURES */
#define arch_this_cpu_read(pcp, op) \
({ \
unsigned long lc_pcpr, lc_pcpo, res__; \
typedef typeof(pcp) pcp_op_T__; \
pcp_op_T__ *ptr__; \
\
lc_pcpr = offsetof(struct lowcore, percpu_register); \
lc_pcpo = offsetof(struct lowcore, percpu_offset); \
ptr__ = PERCPU_PTR(&(pcp)); \
asm_inline volatile( \
MVIY_PERCPU("%[disppcpr]", "%[dispaltpcpr]", "%[ptr__]")\
AG_ALT("%[disppcpo]", "%[dispaltpcpo]", "%[ptr__]") \
op " %[res__],0(%[ptr__])\n" \
MVIY_ALT("%[disppcpr]", "%[dispaltpcpr]") \
: [res__] "=&d" (res__), [ptr__] "+&a" (ptr__), \
"=m" (((struct lowcore *)0)->percpu_register) \
: [disppcpr] "i" (lc_pcpr), \
[disppcpo] "i" (lc_pcpo), \
[dispaltpcpr] "i" (lc_pcpr + LOWCORE_ALT_ADDRESS), \
[dispaltpcpo] "i" (lc_pcpo + LOWCORE_ALT_ADDRESS), \
"m" (*ptr__), \
"m" (((struct lowcore *)0)->percpu_offset) \
: "cc"); \
(pcp_op_T__)res__; \
})
#define this_cpu_read_1(pcp) arch_this_cpu_read(pcp, "llgc")
#define this_cpu_read_2(pcp) arch_this_cpu_read(pcp, "llgh")
#define this_cpu_read_4(pcp) arch_this_cpu_read(pcp, "llgf")
#define this_cpu_read_8(pcp) arch_this_cpu_read(pcp, "lg")
#define arch_this_cpu_cmpxchg(pcp, oval, nval) \
({ \
typedef typeof(pcp) pcp_op_T__; \