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ARRAY_BIST requires the test to be invoked only from one of the HT siblings of a core. If the other sibling was in mwait(), that didn't permit the test to complete and resulted in several retries before the test could finish. The exit rendezvous was introduced to keep the HT sibling busy until the primary CPU completed the test to avoid those retries. What is actually needed is to ensure that both the threads rendezvous *before* the wrmsr to trigger the test to give good chance to complete the test. The `stop_machine()` function returns only after all the CPUs complete running the function, and provides an exit rendezvous implicitly. In kernel/stop_machine.c::multi_cpu_stop(), every CPU in the mask needs to complete reaching MULTI_STOP_RUN. When all CPUs complete, the state machine moves to next state, i.e MULTI_STOP_EXIT. Thus the underlying API stop_core_cpuslocked() already provides an exit rendezvous. Add the rendezvous earlier in order to ensure the wrmsr is triggered after all CPUs reach the do_array_test(). Remove the exit rendezvous since stop_core_cpuslocked() already guarantees that. Signed-off-by: Ashok Raj <ashok.raj@intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> Link: https://lore.kernel.org/r/20240125082254.424859-5-ashok.raj@intel.com Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.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 Restructured Text 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.