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Message-ID: <47AB120A.1000600@wpkg.org>
Date: Thu, 07 Feb 2008 15:13:30 +0100
From: Tomasz Chmielewski <mangoo@...g.org>
To: LKML <linux-kernel@...r.kernel.org>
Subject: why kexec insists on syncing with recent kernels?
According to kernel/kexec.c:
* kexec does not sync, or unmount filesystems so if you need
* that to happen you need to do that yourself.
I saw this was true with 2.6.18 kernel (i.e., it didn't sync), but kexec
syncs with recent kernels (I checked 2.6.23.14 and 2.6.24):
# kexec -e
md: stopping all md devices
sd 2:0:0:0: [sdb] Synchronizing SCSI cache
With kexec on 2.6.18 it was executing a loaded kernel immediately.
Generally, it's a good thing to sync before jumping into a new kernel,
but it breaks my setup here after upgrading from 2.6.18 to 2.6.24.
Why?
I have a couple of diskless (iSCSI-boot) machines with a buggy BIOS (old
Supermicro P4SBR/P4SBE) which randomly freeze after rebooting (the
machine shuts down just fine, but instead of booting again, showing BIOS
bootup messages etc. you can just see blank screen).
Therefore, I use kexec as a workaround for this rebooting problem.
The way kexec works now makes rebooting unreliable again:
- network interfaces are brought down,
- kernel tries to sync - it never will, as we're booted off network,
which is down
Any ideas why kexec insists on syncing?
--
Tomasz Chmielewski
http://blog.wpkg.org
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