hwmon: (coretemp) Fix handling of isolated SMT siblings

Commit 0f8b916bc5b5 ("hwmon: (coretemp) avoid RDMSR interrupts to
isolated CPUs") prevents create_core_data() from creating temperature
data for an isolated CPU. coretemp_cpu_online(), however, still adds
that CPU to pdata->cpumask.

When an isolated SMT thread is processed before a housekeeping sibling,
the mask makes coretemp_cpu_online() believe that the core is already
represented. The housekeeping sibling then gets no temperature
attributes. Package attributes are similarly not retried when the first
CPU processed in a die is isolated.

The mask is also used to select a replacement CPU when a sensor target
goes offline. Including isolated CPUs permits the driver to retarget a
sensor to one, causing subsequent sysfs reads to send an RDMSR IPI to an
isolated CPU.

Keep isolated CPUs out of pdata->cpumask by moving the housekeeping check
to coretemp_cpu_online(). Sensor creation is then deferred to an eligible
CPU, and hotplug replacement targets remain on housekeeping CPUs.

Tested on an Intel Core i7-10510U running 6.18.50-3-cachyos-lts, with
nohz_full=1 on CPU 1 and its housekeeping SMT sibling on CPU 5. The stock
driver omitted Core 1 after module load and retained its readable sensor
after CPU 5 was offlined. The patched driver exposed Core 1, removed it
when CPU 5 went offline, and restored it when CPU 5 returned.

Fixes: 0f8b916bc5b5 ("hwmon: (coretemp) avoid RDMSR interrupts to isolated CPUs")
Cc: stable@vger.kernel.org
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Ximing Zhang <xzhangjr@gmail.com>
Tested-by: Asaf Nuri Bertizlioğlu <ycistak@gmail.com>
Link: https://patch.msgid.link/20261016-codex-coretemp-housekeeping-v1-1-96618c5676b2@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

0 files changed, 0 insertions, 0 deletions