POSIX personality
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"Andi" == Andi Kleen <[email protected]> writes:
Quoted 10 lines · Andi> Dave McCracken <[email protected]> writes:
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--On Tuesday, May 21, 2002 01:52:37 PM -0700 Linus Torvalds
Quoted 1 line · <[email protected]> wrote:
I don't see any reason to start using some fixed-mode semantics
without > seeing some stronger arguments on exactly why that would be a good idea. > We have used up 11 of 24 bits (and more can be made available) over the > last five years, and there are no obvious inefficiencies that I can see.
Ok, sounds reasonable. I'll add the bits as I go, then.
Andi> One reason for it would be that it would be more efficient. All Andi> the various shared state needed for POSIX thread group emulation Andi> could be put into a single structure with a single reference Andi> count.
Andi> With clone flags you need one pointer in task_struct per flag Andi> and handling of the reference count for each data structure and Andi> allocation/freeing from various slabs for a real fork. Andi> (basically lots of atomic operations at fork time + bloating of Andi> task_struct)
With one minor restriction, you could do it the same way SGI's IRIX
handled sproc() --- have a struct shared that was pointed to by the
task structure, that was then partially or completely populated
depending on the sharing flags. The struct shared can also have a
list of tasks that share stuff in it. Each task has a set of flags to say what's being shared.
You'd have to disallow sharing things that a task's parent doesn't share with the task, if the parent and the child are part of the same share group.
Peter C