lkml.org 
[lkml]   [2009]   [Jul]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] sysrq, kdump: fix regression, revert "simplify sysrq-c handler"
Eric W. Biederman wrote:
> Lai Jiangshan <laijs@cn.fujitsu.com> writes:
>
>> 1) This fix breaks our tools.
>> This fix changes the ABI. panic_on_oops is default 0,
>> and a lots system do not specify the boot option "panic",
>> thus, Sysrq-c will not cause CrashDump(Kdump) as expected.
>
> How does it break your tools?

Sysrq-c is known for causing a CrashDump.
This fix make Sysrq-c just causing an oops.
An oops in process context just kills current task and
does nothing. (panic_on_oops=0)

Why we let a cleanup patch changes the kernel behavior so much?

>
>> 2) When CONFIG_KEXEC=n, Sysrq-c should become an invalid
>> command like Sysrq-D(CONFIG_LOCKDEP, show-all-locks).
>> But this fix makes it a valid command and let it do a
>> hazard thing: cause a page fault(NULL dereference) in kernel.
>>
>> So, we revert this fix.
>
> The idea was to extend sysrq-d to also be a way of testing NULL
> pointer dereferences. How is that a bad idea?
>

When CONFIG_KEXEC=n, Crashdump is not available,
Sysrq-c should become an invalid command.




\
 
 \ /
  Last update: 2009-07-21 08:03    [W:0.139 / U:0.604 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site