Ns critsec

2008-08-29T15:39:55Z

Hcd000:

Man page: http://aolserver.com/docs/tcl/ns_critsec.html

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'''NAME'''

: ns_critsec - Operate on critical section objects

'''SYNOPSIS'''

: '''ns_critsec''' ''option ?arg arg ...?''

'''DESCRIPTION'''

: This command provides a mechanism to manipulate critical section objects. The legal ''option''s (which may be abbreviated) are:
* '''ns_critsec create'''

: Initializes a new critical section object and returns a handle to it.
* '''ns_critsec destroy''' ''object''

: Destroys the critical section object and frees any resources it was using.
* '''ns_critsec enter''' ''object''

: Enters the critical section. The thread will block if another thread is already in the critical section.
* '''ns_critsec leave''' ''object''

: Leaves the critical section. When the thread leaves the critical section as many times as it has entered, a notification will be sent to other threads that are waiting on the critical section.

'''EXAMPLES'''

Is this the right way to use this command? The example is contrived, but I wanted to call ns_critsec multiple times.

# If a thread is executing any of these procs, no other
# thread can execute any of these procs until the first
# thread has completely finished.

nsv_set . special_file_critsec [ns_critsec create]

proc write_special_file {data} {
set critsec [nsv_get . special_file_critsec]
ns_critsec enter $critsec
set handle [open special_file w]
puts $handle $data
close $handle
ns_critsec leave $critsec
}

proc read_special_file {} {
set critsec [nsv_get . special_file_critsec]
ns_critsec enter $critsec
set handle [open special_file r]
set result [read $handle]
close $handle
ns_critsec leave $critsec
return $result
}

proc change_special_file {data} {
set critsec [nsv_get . special_file_critsec]
ns_critsec enter $critsec
set result [read_special_file]
write_special_file $data
ns_critsec leave $critsec
return $result
}

'''SEE ALSO'''

: [[ns_cond]], [[ns_event]], [[ns_mutex]], [[ns_thread]]

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[[Category Documentation]] - [[Category Core Tcl API]]

AOLserver Wiki - User contributions [en]

Ns critsec