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a786ef152c
The threshold in tsc_read_refs() is constant which may favor slower CPUs but may not be optimal for simple reading of reference on faster ones. Hence make it proportional to tsc_khz when available to compensate for this. The threshold guards against any disturbance like IRQs, NMIs, SMIs or CPU stealing by host on guest systems so rename it accordingly and fix comments as well. Also on some systems there is noticeable DMI bus contention at some point during boot keeping the readout failing (observed with about one in ~300 boots when testing). In that case retry also the second readout instead of simply bailing out unrefined. Usually the next second the readout returns fast just fine without any issues. Signed-off-by: Daniel Vacek <neelx@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Link: https://lkml.kernel.org/r/1541437840-29293-1-git-send-email-neelx@redhat.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.