ACPI/processor: Replace racy task affinity logic

acpi_processor_get_throttling() requires to invoke the getter function on
the target CPU. This is achieved by temporarily setting the affinity of the
calling user space thread to the requested CPU and reset it to the original
affinity afterwards.

That's racy vs. CPU hotplug and concurrent affinity settings for that
thread resulting in code executing on the wrong CPU and overwriting the
new affinity setting.

acpi_processor_get_throttling() is invoked in two ways:

1) The CPU online callback, which is already running on the target CPU and
   obviously protected against hotplug and not affected by affinity
   settings.

2) The ACPI driver probe function, which is not protected against hotplug
   during modprobe.

Switch it over to work_on_cpu() and protect the probe function against CPU
hotplug.

Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Sebastian Siewior <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: [email protected]
Cc: Viresh Kumar <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Len Brown <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

0 files changed, 0 insertions, 0 deletions