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| author | Mark Rutland <mark.rutland@arm.com> | 2016-11-03 20:23:11 (GMT) |
|---|---|---|
| committer | Alex Shi <alex.shi@linaro.org> | 2017-05-27 03:16:16 (GMT) |
| commit | ac6ed41247a773883782d2c8c73f9a1e98d764d3 (patch) | |
| tree | 1f18abdf15c24c49d200ffc90fd563c7d165467f /arch/arm64/kernel | |
| parent | ebff883d279a34258040928ff863d16c7f17fb58 (diff) | |
| download | linux-ac6ed41247a773883782d2c8c73f9a1e98d764d3.tar.xz | |
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: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura 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: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 57c82954e77fa12c1023e87210d2ede77aaa0058)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
Diffstat (limited to 'arch/arm64/kernel')
| -rw-r--r-- | arch/arm64/kernel/smp.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index f64401f..6f42c68 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -58,6 +58,9 @@ #define CREATE_TRACE_POINTS #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 * 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) */ for_each_possible_cpu(cpu) { + per_cpu(cpu_number, cpu) = cpu; + if (cpu == smp_processor_id()) continue; |