[Tcl-bugs] [ tcl-Feature Requests-674367 ] call for a function that is not thread safe

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Feature Requests item #674367, was opened at 2003-01-25 00:39
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Category: 80. Thread Package
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Markus Elfring (elfring)
Assigned to: Zoran Vasiljevic (vasiljevic)
Summary: call for a function that is not thread safe

Initial Comment:
I describe an use case for the handling of unsafe functions calls with 
the thread package.

I must assume that an application 
programming interface (like a graphics library or a music API) or even 
a single function is not thread safe if this property is not described in the 
documentation for that API.
So I must ensure that all unsafe 
functions are executed by a single thread at each time. I want to create a 
thread for each function library that must be handled as it has not 
implemented thread safety at startup/initialization time of my 
application. I want to achieve that calls into different unsafe libraries 
can be executed simultaneously.

I can perform the call with the 
function "thread::send" for a thread that has been created before. But I 
think that I will need a special kind of mutual exclusion. I understand the 
thread package's documentation in the way that a mutex that is created 
by the command "thread::mutex create" belongs to the calling thread. 
It may not be stored in a thread shared variable. Please correct me if I 
make wrong assumptions here.

I guess that the function 
"thread::eval" does not all what I want and need here. It does not expect 
a thread indentifier in its argument list.
I need a mutex that is global to 
the process scope 
(http://citeseer.nj.nec.com/cs?cs=1&q=synchronization+and+global+and+mutex&submit=Documents&co=Expected+Citations&cm=50&cf=Any&ao=Expected+Citations&am=20&af=Any
) 
to perform a protected and synchronous call of a code piece that 
should be executed by an other thread.
I would like to suggest new 
functions like the following.

1. thread::mutex::create 
global
         or
   thread::mutex -global create

2. 
thread::safecall id global_mutex script ?varname?


How 
do you think about this suggestion?
Does this use case lead to add 
more synchronization primitives to the thread package?

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>Comment By: Markus Elfring (elfring)
Date: 2003-01-25 10:10

Message:
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user_id=572001

Values are only available globally with TCL threads if the data is stored in 
thread shared variables. (http://cvs.sourceforge.net/cgi-
bin/viewcvs.cgi/*checkout*/tcl/thread/doc/html/tsv.html).

So I 
adjust my suggestion for the function interface design. The identifier for the 
mutex object with the global scope must be accessed by a thread shared 
variable.

1. thread::mutex::create ?tsvname 
...?

2.
thread::safecall id tsvname script ?varname?

----------------------------------------------------------------------

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