[PATCH v2 1/2] remote: Use `catch' in killing pending force-kills

Address an execution race in `close_wait_program' and use `catch' in 
killing pending force-kills issued there in the recovery of a stuck test 
case, in case the force-kill sequence has completed before the command 
to kill the sequence had a chance to run, so that no error is thrown and 
a testsuite run does not get interrupted early like:

PASS: gcc.c-torture/execute/postmod-1.c   -O0  (test for excess errors)
Executing on remote-localhost: .../gcc/testsuite/gcc/postmod-1.exe    (timeout = 15)
spawn [open ...]
WARNING: program timed out
ERROR: tcl error sourcing .../gcc/testsuite/gcc.c-torture/execute/execute.exp.
ERROR: child process exited abnormally
    while executing
"exec sh -c "exec > /dev/null 2>&1 && kill -9 $exec_pid""
    (procedure "close_wait_program" line 57)
    invoked from within
"close_wait_program $spawn_id $pid wres"
    (procedure "local_exec" line 104)
[...]
"uplevel #0 source .../gcc/testsuite/gcc.c-torture/execute/execute.exp"
    invoked from within
"catch "uplevel #0 source $test_file_name""
testcase .../gcc/testsuite/gcc.c-torture/execute/execute.exp completed in 196 seconds

		=== gcc Summary ===

# of expected passes		1

-- therefore not letting `execute.exp' continue (here with the GCC `c' 
testsuite invoked with `execute.exp=postmod-1.c' for 8 compilation and 8 
execution tests).

The completion of the force-kill sequence would have to happen in the 
window between the `wait' command has returned, which would at worst 
happen as a result of the final `kill -9' command in the sequence, and 
the `kill -9 $exec_pid' command issued here, and the `sleep 5' command 
issued at the end of the force-kill sequence makes the likelihood of 
such a scenario low, but this might still happen with a loaded host 
system and there is no drawback from using `catch' here, so let's do it.

	* lib/remote.exp (close_wait_program): Use `catch' in killing 
	pending force-kills.

Signed-off-by: Maciej W. Rozycki <[email protected]>
---
Hi,

 Please apply.  FAOD this has been formatted for `git am' use.

  Maciej

Changes from v1:

- Simplify `catch' invocation, no functional change.
---
 lib/remote.exp |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

dejagnu-remote-close-wait-kill-catch.diff
Index: dejagnu/lib/remote.exp
===================================================================
--- dejagnu.orig/lib/remote.exp
+++ dejagnu/lib/remote.exp
@@ -113,7 +113,10 @@ proc close_wait_program { program_id pid
 	# We reaped the process, so cancel the pending force-kills, as
 	# otherwise if the PID is reused for some other unrelated
 	# process, we'd kill the wrong process.
-	exec sh -c "exec > /dev/null 2>&1 && kill -9 $exec_pid"
+	#
+	# Use `catch' in case the force-kills have completed, so as not
+	# to cause TCL to choke if `kill' returns a failure.
+	catch {exec sh -c "kill -9 $exec_pid" >& /dev/null}
     }
 
     return $res