[Bug testsuite/31312] attach-many-short-lived-threads gives inconsistent results

["cel at linux dot ibm.com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31312

--- Comment #15 from Carl E Love <cel at linux dot ibm.com> ---

Tommy:

I spent some time trying to dig into this again.

The gdb log says that it detached from the pid.  I don't find any way to verify
that.  I don't see any gdb attached thread status command that would verify it. 

I did try putting in sleep commands in the hope that if it was a race of trying
to delay the attach a bit more to give time for the detach to really finish. 
But that didn't make any difference.

I was able to get the expect script to issue the ps command on the fail so I
can go look at the processes running:

                   if {$eperm} {
                        xfail "$test (EPERM)"
                        # The attach failed.  No point in doing the rest        
                        # of the tests since we are not attached?  So           
                        # should we either 1) exit the test; or 2)              
                        # try again with a new testpid?                         
                        puts "CARLL, xfail EPERM, testpid $testpid"

                        gdb_test "detach" "Detaching from.*"

                        # try to figure out the state of the process            
                        set prompt {\$ $}
                        spawn bash
                        expect -re $prompt
                        send "ps -eaf \r"
                        expect {
                            "aa" {
                                send "CARLL, Output\r"
                            }
                            -re $prompt
                        }
                        expect eof

Based on the ps output, it does look like the process is still running.

With regards to my patch, you mentioned that you were concerned about leaving
the process running and then starting another one. Perhaps we should kill the
process that we couldn't attach to then create a new one?  That way we
shouldn't 
be leaving anything running.  Specifically:

                -re "$gdb_prompt $" {
                    if {$eperm} {
                        xfail "$test (EPERM)"
                        # Kill the current process and start a new one    <<
NEW                           
                        kill_wait_spawned_process $test_spawn_id          <<
NEW

                        # The attach failed.  No point in doing the rest        
                        # of the tests since we are not attached?  So           
                        # should we either 1) exit the test; or 2)              
                        # try again with a new testpid?                         
                        puts "CARLL, xfail EPERM, testpid $testpid"

                        # Try a new process                                     
                        set test_spawn_id [spawn_wait_for_attach $binfile]
                        set testpid [spawn_id_get_pid $test_spawn_id]
                    } else {
                        pass $test
                    }
                }

We could just end the test as you suggested.  That is still another option.  

Thoughts on killing the previous thread and then creating a new one?  Or would
you still prefer just ending the test?

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