(this can be used for general discussion of per-thread data)
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[CMcC] Each of the following [tcl core subsystems] contains Thread Specific Data:

    * tclFileName
    * tclIO ([Tcl Core IO System])
    * tclNotify
    * tclAsync
    * tclEvent
    * tclTimer
    * and even tclRegexp

It's used, somewhat like ClientData, to store per-thread quasi-global arbitrary data,
which is required to maintain state, and used to clean up on termination
or [Finalization] as it is called in the tcl [core].

This is useful, because it helps modularise each subsystem, however the very encapsulation
makes it impossible to extend or modify the subsystems additively, which would make it easier to
test subsystem mods without pulling apart entire subsystems.

I'm writing a TIP on this subject.

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[LV] In Jan, 2007, on the [starkit] mailing list, a user asked about problems
between [thread]s and [vfs]. [JH] replied that vfs mount points are not
shared between threads by design to try to limit easy crash conditions.
If a particular vfs mount point is needed, it should be mounted within
the thread.

As with all packages, once loaded in any interp, they are available 
statically to all others.

 hobbit [~] 4 % /Library/Tcl/basekits/base-tcl-thread-macosx-universal
 % package require Thread
 2.6.5
 % set t [thread::create {thread::wait}]
 tid0x1804e00
 % package require vfs
 1.3
 % thread::send $t {load {} vfs}
 % thread::send $t {package names}
 Thread tclkitpath zlib vfs Mk4tcl Tcl


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I think there's a typo.  Previously loaded libraries are statically available to other interpreters, but packages aren't. In order to mount a [vfs], you need more than just the base [vfs] library, you in general also need tcl package(s).  And if you're running in a [Starpack], where all the packages are stored in a [vfs], it becomes a chicken-and-egg problem.

(Run from within a [Starpack])
 % package require Thread
 2.6.5
 % set t [thread::create {thread::wait}]
 tid00000A8C
 % thread::send $t {load {} vfs}
 % thread::send $t {load {} vfs::mk4}
 package "vfs::mk4" isn't loaded statically
 % thread::send $t {vfs::mk4::Mount foo.exe foo}
 invalid command name "vfs::mk4::Mount"

So the thread can't "package require vfs::mk4" until after the thread has mounted the [Starpack], but the thread can't mount the [Starpack] until after it has successfully executed "package require vfs::mk4".

Unless there's some other mechanism to expose the [vfs] to a thread (perhaps by copying the [Thread Specific Data]?), it seems as though threads now have *very* limited functionality in a [Starpack].

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[Category Threads]