Re: [...] kprobes [minutes] portion 20060406

[Richard J Moore <richardj_moore at uk dot ibm dot com>]

Unfortunately I missed the discussion. Am I right in deducing that
user-space probes as being discussed here are designed or intended as
probes for use with an application's perspective? If so, I believe that is
wrong or at least only attending to part of the need. For me the real
benefit of user-space probes is to provide an  extension to a kernel probe
that gives it full access to the system.  The arguments on lkml put forward
by Christoph and Arjan have value when one thinks of a user-probe only
serving user-space code and a user-space problem.  But we have tools
already in place to deal with that.  Have we fully appreciated the need
when addressing certain system or kernel problems that one needs access to
full system resources, which will include user-space code and data.  Anyone
who works on performance problems (hangs being an extreme example)
involving the networking stack will corroborate this need. An more
generally anyone that works with a kernel-based server component of a
client-server model will also corroborate this need.

Richard

- -
Richard J Moore
IBM Advanced Linux Response Team - Linux Technology Centre
MOBEX: 264807; Mobile (+44) (0)7739-875237
Office: (+44) (0)1962-817072


                                                                           
             "Frank Ch.                                                    
             Eigler"                                                       
             <fche@redhat.co                                            To 
             m>                       Hien Q Nguyen <nguyhien@us.ibm.com>  
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                                                                   Subject 
             06/04/2006               Re: [...] kprobes [minutes] portion  
             22:28                    20060406                             
                                                                           
                                                                           




Hi -

On Thu, Apr 06, 2006 at 02:14:46PM -0700, Hien Q Nguyen wrote:
> User space probe
> Prasanna had prototype that execute the handler in the user space [...]

Beyond merely dispatching, it is important to consider what such a
handler can do.  Would it still be useful if it cannot call into the
kernel-side runtime, if it cannot share variables with kernel-space
probes?


- FChE