Re: [patch 1/2] x86_64 page fault NMI-safe

[Masami Hiramatsu]

Peter Zijlstra wrote:
> On Wed, 2010-08-04 at 10:45 -0400, Mathieu Desnoyers wrote:
> 
>> How do you plan to read the data concurrently with the writer overwriting the
>> data while you are reading it without corruption ?
> 
> I don't consider reading while writing (in overwrite mode) a valid case.
> 
> If you want to use overwrite, stop the writer before reading it.

For example, would you like to read system audit log always after
stop the audit?

NO, that's a most important requirement for tracers, especially for
system admins (they're the most important users of Linux) to check
the system health and catch system troubles.

For performance measurement and checking hotspot, one-shot tracing
is enough. But it's just for developers. But for the real world
computing, Linux is just an OS, users want to run their system,
middleware and applications, without troubles. But when they hit
a trouble, they wanna shoot it ASAP.
The flight recorder mode is mainly for those users.

Thank you,

-- 
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@xxxxxxxxxxx
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