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Re: [PATCH] arm64: make secondary_start_kernel() notrace




On 12/06/18 10:07, Zhizhou Zhang wrote:
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

Signed-off-by: Zhizhou Zhang <zhizhouzhang@xxxxxxxxxxxx>
---
  arch/arm64/kernel/smp.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index f3e2e3ae..11b0f30 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -179,7 +179,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
   * 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)
+notrace asmlinkage void secondary_start_kernel(void)
  {
  	u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
  	struct mm_struct *mm = &init_mm;


Tested-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>

I think this should go to stable releases as well.

Suzuki