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Linux kernel stable tree
9861f7f66f
Currently, the CONFIG_CSD_LOCK_WAIT_DEBUG code uses sched_clock() to check for excessive CSD-lock wait times. This works, but does not guarantee monotonic timestamps on x86 due to the sched_clock() function's use of the rdtsc instruction, which does not guarantee ordering. This means that, given successive calls to sched_clock(), the second might return an earlier time than the second, that is, time might seem to go backwards. This can (and does!) result in false-positive CSD-lock wait complaints claiming almost 2^64 nanoseconds of delay. Therefore, switch from sched_clock() to ktime_get_mono_fast_ns(), which does guarantee monotonic timestamps via the rdtsc_ordered() function, which as the name implies, does guarantee ordered timestamps, at least in the absence of calls from NMI handlers, which are not involved in this code path. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Rik van Riel <riel@surriel.com> Cc: Neeraj Upadhyay <neeraj.upadhyay@kernel.org> Cc: Leonardo Bras <leobras@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> |
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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.