Jarrett Farnitano a8311f647e kexec: yield to scheduler when loading kimage segments
Without yielding while loading kimage segments, a large initrd will
block all other work on the CPU performing the load until it is
completed.  For example loading an initrd of 200MB on a low power single
core system will lock up the system for a few seconds.

To increase system responsiveness to other tasks at that time, call
cond_resched() in both the crash kernel and normal kernel segment
loading loops.

I did run into a practical problem.  Hardware watchdogs on embedded
systems can have short timers on the order of seconds.  If the system is
locked up for a few seconds with only a single core available, the
watchdog may not be pet in a timely fashion.  If this happens, the
hardware watchdog will fire and reset the system.

This really only becomes a problem when you are working with a single
core, a decently sized initrd, and have a constrained hardware watchdog.

Link: http://lkml.kernel.org/r/1528738546-3328-1-git-send-email-jmf@amazon.com
Signed-off-by: Jarrett Farnitano <jmf@amazon.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-06-15 07:55:24 +09:00

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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.
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