Messages in this thread | | | From | (Eric W. Biederman) | Date | Mon, 20 Jul 2009 23:56:22 -0700 | Subject | Re: [PATCH] sysrq, kdump: fix regression, revert "simplify sysrq-c handler" |
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Lai Jiangshan <laijs@cn.fujitsu.com> writes:
> 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?
Because it seemed reasonable to be able to test the oops path as well.
>>> 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.
Why should sysrq-c become an invalid command?
What problem does this cause for you?
Eric
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