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cpu_primary_thread_mask is only defined when CONFIG_SMP=y. However, even
in UP kernels there is always exactly one CPU, which can reasonably be
treated as the primary thread.
Historically, topology_is_primary_thread() always returned true with
CONFIG_SMP=n. A recent commit:
4b455f5994 ("cpu/SMT: Provide a default topology_is_primary_thread()")
replaced it with a generic implementation with the note:
"When disabling SMT, the primary thread of the SMT will remain
enabled/active. Architectures that have a special primary thread (e.g.
x86) need to override this function. ..."
For consistency and clarity, make the primary thread mask available
regardless of SMP, similar to cpu_possible_mask and cpu_present_mask.
Move __cpu_primary_thread_mask into common code to prevent build issues.
Let cpu_mark_primary_thread() configure the mask even for UP kernels,
alongside other masks. Then, topology_is_primary_thread() can
consistently reference it.
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20250320234104.8288-1-chang.seok.bae@intel.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.