Re: utrace vs. ptrace

[Martin Bligh <mbligh@mbligh.org>]

Alan Cox wrote:
> On Iau, 2006-07-13 at 12:05 -0700, Linus Torvalds wrote:
> 
>>Doing core-dumping in user space would be insane. It doesn't give _any_ 
>>advantages, only disadvantages.
> 
> 
> It has a number of very real advantages in certain circumstances and the
> only interface the kernel needs to provide is the debugger interface and
> something to "kick" the debugger and reparent to it, or for that matter
> it might even be viable just to pass the helper the fd of an anonymous
> file holding the dump.
> 
> Taking out the kernel core dump support would be insane.
> 
> We get customers who like to collect/process/do clever stuff with core
> dumps and failure cases. We also get people who want to dump a core that
> excludes the 14GB shared mmap of the database file as another example
> where it helps.

The in-kernel core dumper also seems to hold locks that wedge access
to /proc for that pid, which causes anything walking /proc to wedge.
For large core dumps, that takes far too long, and causes us real
problems

M.