Scott Long <[EMAIL PROTECTED]> writes:
> I can also use the LDT to point to thread-specific segments. IMHO this
> is much better than the stack trick used by linuxthreads. The problem
Modern LinuxThreads (glibc 2.2) also uses modify_ldt for thread local data
(much to the pain of the IA64 and x86-64 ports who have to emulate it..)
> is, I don't fully understand how to use modify_ldt(). Is anyone
> knowledgeable about this?
modify_ldt() works like a memcpy to/from the ldt. See the man page. On the
layout of the LDT see the intel IA32 architecture manual from
http://developer.intel.com
> If anyone has any other suggestions, please let me know. If you are
> confused as to why I would ever want to do this in the first place, I'd
> be willing to go over it off the list.
I can imagine, but it'll cost you. Most modern CPUs have heavy penalties for
non-zero-based or limited segments (a few cycles for every memory access) and LDT
switching also makes the context switch slower.
An portable alternative is to use multiple processes with a shared memory area.
-Andi
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