Commit a8311f64 authored Jun 14, 2018 by Jarrett Farnitano Committed by Linus Torvalds Jun 15, 2018

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>

parent 92ee383f

kernel/kexec_core.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -829,6 +829,8 @@ static int kimage_load_normal_segment(struct kimage *image,
		else
		buf += mchunk;
		mbytes -= mchunk;

		cond_resched();
		}
		out:
		return result;
		@@ -893,6 +895,8 @@ static int kimage_load_crash_segment(struct kimage *image,
		else
		buf += mchunk;
		mbytes -= mchunk;

		cond_resched();
		}
		out:
		return result;

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