Hi,
I need a bit of help sorting this out...
I have a memory test script that is a bit of compiled C. The test itself
can only ever return a 0 or 1 exit code, this is explicitly coded and there
are no other options.
I also have a wrapper test script that calls the C program that should also
only return 0 or 1 on completion.
The problem i'm encountering, however, involves the return code when
subprocess.poll() is called against the running memory test process. The
current code in my wrapper program looks like this:
def run_processes(self, number, command):
passed = True
pipe = []
for i in range(number):
pipe.append(self._command(command))
print "Started: process %u pid %u: %s" % (i, pipe[i].pid,
command)
sys.stdout.flush()
waiting = True
while waiting:
waiting = False
for i in range(number):
if pipe[i]:
line = pipe[i].communicate()[0]
if line and len(line) > 1:
print "process %u pid %u: %s" % (i, pipe[i].pid,
line)
sys.stdout.flush()
if pipe[i].poll() == -1:
waiting = True
else:
return_value = pipe[i].poll()
if return_value != 0:
print "Error: process %u pid %u retuned %u" %
(i, pipe[i].pid, return_value)
passed = False
print "process %u pid %u returned success" % (i,
pipe[i].pid)
pipe[i] = None
sys.stdout.flush()
return passed
So what happens here is that in the waiting loop, if pipe[i].poll returns a
-1, we keep waiting, and then if it returns anything OTHER than -1, we exit
and return the return code.
BUT, I'm getting, in some cases, a return code of 127, which is impossible
to get from the memory test program.
The output from this bit of code looks like this in a failing situation:
Error: process 0 pid 2187 retuned 127
process 0 pid 2187 returned success
Error: process 1 pid 2188 retuned 127
process 1 pid 2188 returned success
I'm thinking that I'm hitting some sort of race here where the kernel is
reporting -1 while the process is running, then returns 127 or some other
status when the process is being killed and then finally 0 or 1 after the
process has completely closed out. I "think" that the poll picks up this
intermediate exit status and immediately exits the loop, instead of waiting
for a 0 or 1.
I've got a modified version that I'm getting someone to test for me now that
changes
if pipe[i].poll() == -1:
waiting = True
to this
if pipe[i].poll() not in [0,1]:
waiting = True
So my real question is: am I on the right track here, and am I correct in my
guess that the kernel is reporting different status codes to
subprocess.poll() during the shutdown of the polled process?
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