CODEWITHSUNDEEP
multithreadingtclsend
Ravikiran Ambati
Ravikiran Ambati

Reputation: 1

TCL: thread::send command is running in main thread instead of thread id mentioned in send command

Below is the example script written for implementing multi threading for my existing single (main thread) threaded scripts.

# Wrapper proc for executing passed procedure list
proc eval_procs {dut_no procList} {
telnet_dut $dut_no ;# proc to change telnet id to $dut_no
puts "thread id: [thread::id]"
foreach procedure [join [list $procList]] {
    eval [join $procedure]
  }
}

for {set i 0} {$i <= 1} {incr i} {            
lappend jointhreadIds [thread::create]            
}

set dutList [list 1 2]
set dutConfigList [list [list "get_port_statistics_mt 1"] [list "c_get_port_statistics_mt 2"]] ;#proc for getting port statistics from switch 1 and 2

for {set i 0} {$i <= 1} {incr i} {            
thread::send -async [lindex $jointhreadIds $i] [eval_procs [lindex $dutList $i] [lindex $dutConfigList $i]]             
}

Two threads are created for calling the same proc (eval_procs) for each switch. But, when the proc is called using the thread::send -async, this proc is called sequentially for switch1 and later for switch2. After printing thread::id in eval_procs, I found that these procs are running in main thread, which is the reason for sequential run.

Any one to help me here, what mistake I am doing here or any other procedure to follow ?

The below post mentions to define the procs in the script while creating thread, but for me I have so many already developed libraries (procs) which are working fine with main thread. So, I can not move all the libraries under the thread::create.

https://stackoverflow.com/a/32154589/13100284

Upvotes: 0

Views: 711

Answers (2)

Donal Fellows
Donal Fellows

Reputation: 137567

In general, any custom procedures (or C commands) you create in your master interpreter are not also created in the interpreters of other threads. You can use the ttrace system of the Thread package to do the replication, but you'll need to explicitly load any extra C commands you need. (I prefer to just put everything required in packages and then just package require in every worker thread as required, but that's more complex.)

package require Ttrace

# Procedures created in here get replicated to current and future threads
ttrace::eval {
    # Wrapper proc for executing passed procedure list
    proc eval_procs {dut_no procList} {
        telnet_dut $dut_no ;# proc to change telnet id to $dut_no
        puts "thread id: [thread::id]"
        foreach procedure [join [list $procList]] {
            eval [join $procedure]
        }
    }
    # You probably need to create the other commands here; I don't know your code, but you can source them just fine
}

# Now, the rest of your code as normal.
for {set i 0} {$i <= 1} {incr i} {
    lappend jointhreadIds [thread::create]
}

set dutList [list 1 2]
set dutConfigList [list [list "get_port_statistics_mt 1"] [list "c_get_port_statistics_mt 2"]]; #proc for getting port statistics from switch 1 and 2

for {set i 0} {$i <= 1} {incr i} {
    thread::send -async [lindex $jointhreadIds $i] [eval_procs [lindex $dutList $i] [lindex $dutConfigList $i]]
}

Note that you probably have other bugs too. And that last command offends me, as it should be using a multi-list foreach and building the command to go to to the other thread with list. Here, I mean it should be something like this:

foreach  t_id $joinThreadIds  dut_no $dutList  dut_config $dutConfigList  {
    # I've split the next line in two for even more clarity
    thread::send -async $t_id [list \
            eval_procs $dut_no $dut_config]
}

Upvotes: 1

Schelte Bron
Schelte Bron

Reputation: 4813

You are executing eval_procs in the current thread and sending the result to the threads to execute. Since eval_procs returns the empty string, the threads effectively do nothing.

You probably want an additional list in there:

thread::send -async [lindex $jointhreadIds $i] \
  [list eval_procs [lindex $dutList $i] [lindex $dutConfigList $i]]

But that will fail, because the eval_procs command is not known in the worker threads. You will have to define that proc in each of the subthreads, rather than in the current one.

Upvotes: 0

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