linux-kernel - [PATCH] kexec: yield to scheduler when loading kimage segments

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Date:   Mon, 11 Jun 2018 10:35:46 -0700
From:   Jarrett Farnitano <jmf@...zon.com>
To:     Eric Biederman <ebiederm@...ssion.com>
Cc:     kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jarrett Farnitano <jmf@...zon.com>
Subject: [PATCH] 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.

Signed-off-by: Jarrett Farnitano <jmf@...zon.com>
---
 kernel/kexec_core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 5616755..8ee07d6 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -783,6 +783,8 @@ static int kimage_load_normal_segment(struct kimage *image,
 		else
 			buf += mchunk;
 		mbytes -= mchunk;
+
+		cond_resched();
 	}
 out:
 	return result;
@@ -847,6 +849,8 @@ static int kimage_load_crash_segment(struct kimage *image,
 		else
 			buf += mchunk;
 		mbytes -= mchunk;
+
+		cond_resched();
 	}
 out:
 	return result;
-- 
2.7.4