kerneloops | automatically collect and submit kernel crash signatures

I finally figured out what was wrong. The difference between __preempt_count and current_task is that first one is defined as an int variable, whereas the 2nd one as a pointer to structure. In other words 1st one is defined as a variable and the 2nd one as a pointer.

Now, looking deeper into per cpu variables, they are just variables allocated by the compiler in separate memory locations, like an array. When per_cpu_ptr for a variable Foo is called, then the macro computes something like Foo[cpu], but that means the per_cpu_ptr needs the actual base address of the variable, meaning the & so that it can compute the relative address value starting from this.

When declaring: foo = per_cpu_ptr(&__preempt_count,cpu) , this address is already given = &__preempt_count

When declaring: bar = per_cpu_ptr(current_task,cpu), this address is not given, as the & is missing here. The current_task is a pointer but not the base address of the current_task array.

In both above cases the argument to per_cpu_ptr is a pointer, but here my understanding was wrong, it was not clear to me what is actually the pointer of the variable I need to pass, now it's clear: I have to pass the base address of the variable(var or pointer doesn't matter) so that the macro can compute the relative address for that cpu.

Therefore the right approaches that work are:

bar = per_cpu(current_task,cpu) which translates into *per_cpu_var(&current_task,cpu)

or directly

bar = *per_cpu_var(&current_task,cpu);

You are sorting by the expression a.name - b.name which for your data is always NaN.

If you are trying to sort alphabetically you might want to see this post:
Javascript - sort objects in an array alphabetically on one property of the array