mm/percpu: conditionally define _shared_alloc_tag via CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU

Recently discovered this entry while checking kallsyms on ARM64:
ffff800083e509c0 D _shared_alloc_tag

If ARCH_NEEDS_WEAK_PER_CPU is not defined(it is only defined for s390 and
alpha architectures), there's no need to statically define the percpu
variable _shared_alloc_tag.

Therefore, we need to implement isolation for this purpose.

When building the core kernel code for s390 or alpha architectures,
ARCH_NEEDS_WEAK_PER_CPU remains undefined (as it is gated by #if
defined(MODULE)).  However, when building modules for these architectures,
the macro is explicitly defined.

Therefore, we remove all instances of ARCH_NEEDS_WEAK_PER_CPU from the
code and introduced CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU to replace the
relevant logic.  We can now conditionally define the perpcu variable
_shared_alloc_tag based on CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU.  This
allows architectures (such as s390/alpha) that require weak definitions
for percpu variables in modules to include the definition, while others
can omit it via compile-time exclusion.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Hao Ge <[email protected]>
Suggested-by: Suren Baghdasaryan <[email protected]>
Acked-by: Alexander Gordeev <[email protected]>	[s390]
Acked-by: Mike Rapoport (Microsoft) <[email protected]>
Cc: Chistoph Lameter <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Dennis Zhou <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: Liam Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Richard Henderson <[email protected]>
Cc: Sven Schnelle <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions