4.9-stable review patch. If anyone has any objections, please let me know.
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From: Zhizhou Zhang zhizhouzhang@asrmicro.com
[ Upstream commit b154886f7892499d0d3054026e19dfb9a731df61 ]
We can't call function trace hook before setup percpu offset. When entering secondary_start_kernel(), percpu offset has not been initialized. So this lead hotplug malfunction. Here is the flow to reproduce this bug:
echo 0 > /sys/devices/system/cpu/cpu1/online echo function > /sys/kernel/debug/tracing/current_tracer echo 1 > /sys/kernel/debug/tracing/tracing_on echo 1 > /sys/devices/system/cpu/cpu1/online
Acked-by: Mark Rutland mark.rutland@arm.com Tested-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Zhizhou Zhang zhizhouzhang@asrmicro.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kernel/smp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -205,7 +205,7 @@ int __cpu_up(unsigned int cpu, struct ta * This is the secondary CPU boot entry. We're using this CPUs * idle thread stack, but a set of temporary page tables. */ -asmlinkage void secondary_start_kernel(void) +asmlinkage notrace void secondary_start_kernel(void) { struct mm_struct *mm = &init_mm; unsigned int cpu = smp_processor_id();