Commit 57c82954 authored by Mark Rutland's avatar Mark Rutland Committed by Catalin Marinas

arm64: make cpu number a percpu variable

In the absence of CONFIG_THREAD_INFO_IN_TASK, core code maintains
thread_info::cpu, and low-level architecture code can access this to
build raw_smp_processor_id(). With CONFIG_THREAD_INFO_IN_TASK, core code
maintains task_struct::cpu, which for reasons of hte header soup is not
accessible to low-level arch code.

Instead, we can maintain a percpu variable containing the cpu number.

For both the old and new implementation of raw_smp_processor_id(), we
read a syreg into a GPR, add an offset, and load the result. As the
offset is now larger, it may not be folded into the load, but otherwise
the assembly shouldn't change much.
Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Tested-by: default avatarLaura Abbott <labbott@redhat.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 580efaa7
...@@ -29,11 +29,20 @@ ...@@ -29,11 +29,20 @@
#ifndef __ASSEMBLY__ #ifndef __ASSEMBLY__
#include <asm/percpu.h>
#include <linux/threads.h> #include <linux/threads.h>
#include <linux/cpumask.h> #include <linux/cpumask.h>
#include <linux/thread_info.h> #include <linux/thread_info.h>
#define raw_smp_processor_id() (current_thread_info()->cpu) DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number);
/*
* We don't use this_cpu_read(cpu_number) as that has implicit writes to
* preempt_count, and associated (compiler) barriers, that we'd like to avoid
* the expense of. If we're preemptible, the value can be stale at use anyway.
*/
#define raw_smp_processor_id() (*this_cpu_ptr(&cpu_number))
struct seq_file; struct seq_file;
......
...@@ -58,6 +58,9 @@ ...@@ -58,6 +58,9 @@
#define CREATE_TRACE_POINTS #define CREATE_TRACE_POINTS
#include <trace/events/ipi.h> #include <trace/events/ipi.h>
DEFINE_PER_CPU_READ_MOSTLY(int, cpu_number);
EXPORT_PER_CPU_SYMBOL(cpu_number);
/* /*
* as from 2.5, kernels no longer have an init_tasks structure * as from 2.5, kernels no longer have an init_tasks structure
* so we need some other way of telling a new secondary core * so we need some other way of telling a new secondary core
...@@ -719,6 +722,8 @@ void __init smp_prepare_cpus(unsigned int max_cpus) ...@@ -719,6 +722,8 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
*/ */
for_each_possible_cpu(cpu) { for_each_possible_cpu(cpu) {
per_cpu(cpu_number, cpu) = cpu;
if (cpu == smp_processor_id()) if (cpu == smp_processor_id())
continue; continue;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment