Message218414
collect_children routine in SocketServer.py contains two possible race conditions. First one is in while loop "while len(self.active_children) >= self.max_children:". If status of child is collected outside of Socket server (for example in signal handler or something), then the variable self.active_children will not match actual child processes and the os.waitpid(0, 0) within the while loop will raise os.error, errno=10 (ECHILD) "No Child Processes". self.active_children should be emptied in this case, otherwise you'll end up with an endless loop comsuming 100% CPU (as happened to us).
The second possible race condition is below in the collect_children routine in the "for child in self.active_children" which contains a statement self.active_children.remove(pid) which would modify the iterator. I do not now about python 2.7, but before this would result in "incorrect iteration".
Original code:
for child in self.active_children:
try:
pid, status = os.waitpid(child, os.WNOHANG)
except os.error:
pid = None
if not pid: continue
try:
self.active_children.remove(pid)
except ValueError, e:
raise ValueError('%s. x=%d and list=%r' % (e.message, pid, self.active_children))
Fixed code:
to_remove = []
for child in self.active_children:
try:
pid, status = os.waitpid(child, os.WNOHANG)
except os.error:
pid = None
if not pid: continue
to_remove.append(pid)
for pid in to_remove:
try:
self.active_children.remove(pid)
except ValueError, e:
raise ValueError('%s. x=%d and list=%r' % (e.message, pid, self.active_children)) |
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Date |
User |
Action |
Args |
2014-05-13 08:49:14 | idsvandermolen | set | recipients:
+ idsvandermolen |
2014-05-13 08:49:14 | idsvandermolen | set | messageid: <1399970954.74.0.599178198558.issue21491@psf.upfronthosting.co.za> |
2014-05-13 08:49:14 | idsvandermolen | link | issue21491 messages |
2014-05-13 08:49:14 | idsvandermolen | create | |
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