[PATCH 5/7] ARM: Stop using TPIDRPRW to hold per_cpu_offset

Keith Packard
2021-09-07T22:01:01Z

We're going to store TPIDRPRW here instead

Signed-off-by: Keith Packard <keithpac@amazon.com>
---
arch/arm/include/asm/percpu.h | 31 -------------------------------
arch/arm/kernel/setup.c | 7 -------
arch/arm/kernel/smp.c | 3 ---
3 files changed, 41 deletions(-)

diff --git a/arch/arm/include/asm/percpu.h b/arch/arm/include/asm/percpu.h
index e2fcb3cfd3de..eeafcd6a3e01 100644
--- a/arch/arm/include/asm/percpu.h
+++ b/arch/arm/include/asm/percpu.h
@@ -7,37 +7,6 @@

register unsigned long current_stack_pointer asm ("sp");

-/*
- * Same as asm-generic/percpu.h, except that we store the per cpu offset
- * in the TPIDRPRW. TPIDRPRW only exists on V6K and V7
- */
-#if defined(CONFIG_SMP) && !defined(CONFIG_CPU_V6)
-static inline void set_my_cpu_offset(unsigned long off)
-{
- /* Set TPIDRPRW */
- asm volatile("mcr p15, 0, %0, c13, c0, 4" : : "r" (off) : "memory");
-}
-
-static inline unsigned long __my_cpu_offset(void)
-{
- unsigned long off;
-
- /*
- * Read TPIDRPRW.
- * We want to allow caching the value, so avoid using volatile and
- * instead use a fake stack read to hazard against barrier().
- */
- asm("mrc p15, 0, %0, c13, c0, 4" : "=r" (off)
- : "Q" (*(const unsigned long *)current_stack_pointer));
-
- return off;
-}
-#define __my_cpu_offset __my_cpu_offset()
-#else
-#define set_my_cpu_offset(x) do {} while(0)
-
-#endif /* CONFIG_SMP */
-
#include <asm-generic/percpu.h>

#endif /* _ASM_ARM_PERCPU_H_ */
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index ca0201635fac..d0dc60afe54f 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -590,13 +590,6 @@ void __init smp_setup_processor_id(void)
for (i = 1; i < nr_cpu_ids; ++i)
cpu_logical_map(i) = i == cpu ? 0 : i;

- /*
- * clear __my_cpu_offset on boot CPU to avoid hang caused by
- * using percpu variable early, for example, lockdep will
- * access percpu variable inside lock_release
- */
- set_my_cpu_offset(0);
-
pr_info("Booting Linux on physical CPU 0x%x\n", mpidr);
}

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 5e999f1f1aea..8ccf10b34f08 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -410,8 +410,6 @@ asmlinkage void secondary_start_kernel(unsigned int cpu, struct task_struct *tas
{
struct mm_struct *mm = &init_mm;

- set_my_cpu_offset(per_cpu_offset(cpu));
-
secondary_biglittle_init();

/*
@@ -495,7 +493,6 @@ void __init smp_cpus_done(unsigned int max_cpus)

void __init smp_prepare_boot_cpu(void)
{
- set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
}

void __init smp_prepare_cpus(unsigned int max_cpus)
--
2.33.0